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Sample records for hybrid exchange-correlation functional

  1. Magnetic Exchange Couplings from Semilocal Functionals Evaluated Nonself-Consistently on Hybrid Densities: Insights on Relative Importance of Exchange, Correlation, and Delocalization.

    Science.gov (United States)

    Phillips, Jordan J; Peralta, Juan E

    2012-09-11

    Semilocal functionals generally yield poor magnetic exchange couplings for transition-metal complexes, typically overpredicting in magnitude the experimental values. Here we show that semilocal functionals evaluated nonself-consistently on densities from hybrid functionals can yield magnetic exchange couplings that are greatly improved with respect to their self-consistent semilocal values. Furthermore, when semilocal functionals are evaluated nonself-consistently on densities from a "half-and-half" hybrid, their errors with respect to experimental values can actually be lower than those from self-consistent calculations with standard hybrid functionals such as PBEh or TPSSh. This illustrates that despite their notoriously poor performance for exchange couplings, for many systems semilocal functionals are capable of delivering accurate relative energies for magnetic states provided that their electron delocalization error is corrected. However, while self-consistent calculations with hybrids uniformly improve results for all complexes, evaluating nonself-consistently with semilocal functionals does not give a balanced improvement for both ferro- and antiferromagnetically coupled complexes, indicating that there is more at play with the overestimation problem than simply the delocalization error. Additionally, we show that for some systems the conventional wisdom of choice of exchange functional mattering more than correlation does not hold. This combined with results from the nonself-consistent calculations provide insight on clarifying the relative roles of exchange, correlation, and delocalization in calculating magnetic exchange coupling parameters in Kohn-Sham Density Functional Theory.

  2. Towards improved local hybrid functionals by calibration of exchange-energy densities

    International Nuclear Information System (INIS)

    Arbuznikov, Alexei V.; Kaupp, Martin

    2014-01-01

    A new approach for the calibration of (semi-)local and exact exchange-energy densities in the context of local hybrid functionals is reported. The calibration functions are derived from only the electron density and its spatial derivatives, avoiding spatial derivatives of the exact-exchange energy density or other computationally unfavorable contributions. The calibration functions fulfill the seven more important out of nine known exact constraints. It is shown that calibration improves substantially the definition of a non-dynamical correlation energy term for generalized gradient approximation (GGA)-based local hybrids. Moreover, gauge artifacts in the potential-energy curves of noble-gas dimers may be corrected by calibration. The developed calibration functions are then evaluated for a large range of energy-related properties (atomization energies, reaction barriers, ionization potentials, electron affinities, and total atomic energies) of three sets of local hybrids, using a simple one-parameter local-mixing. The functionals are based on (a) local spin-density approximation (LSDA) or (b) Perdew-Burke-Ernzerhof (PBE) exchange and correlation, and on (c) Becke-88 (B88) exchange and Lee-Yang-Parr (LYP) correlation. While the uncalibrated GGA-based functionals usually provide very poor thermochemical data, calibration allows a dramatic improvement, accompanied by only a small deterioration of reaction barriers. In particular, an optimized BLYP-based local-hybrid functional has been found that is a substantial improvement over the underlying global hybrids, as well as over previously reported LSDA-based local hybrids. It is expected that the present calibration approach will pave the way towards new generations of more accurate hyper-GGA functionals based on a local mixing of exchange-energy densities

  3. Importance of the correlation contribution for local hybrid functionals: range separation and self-interaction corrections.

    Science.gov (United States)

    Arbuznikov, Alexei V; Kaupp, Martin

    2012-01-07

    Local hybrid functionals with their position-dependent exact-exchange admixture are a conceptually simple and promising extension of the concept of a hybrid functional. Local hybrids based on a simple mixing of the local spin density approximation (LSDA) with exact exchange have been shown to be successful for thermochemistry, reaction barriers, and a range of other properties. So far, the combination of this generation of local hybrids with an LSDA correlation functional has been found to give the most favorable results for atomization energies, for a range of local mixing functions (LMFs) governing the exact-exchange admixture. Here, we show that the choice of correlation functional to be used with local hybrid exchange crucially influences the parameterization also of the exchange part as well as the overall performance. A novel ansatz for the correlation part of local hybrids is suggested based on (i) range-separation of LSDA correlation into short-range (SR) and long-range (LR) parts, and (ii) partial or full elimination of the one-electron self-correlation from the SR part. It is shown that such modified correlation functionals allow overall larger exact exchange admixture in thermochemically competitive local hybrids than before. This results in improvements for reaction barriers and for other properties crucially influenced by self-interaction errors, as demonstrated by a number of examples. Based on the range-separation approach, a fresh view on the breakdown of the correlation energy into dynamical and non-dynamical parts is suggested.

  4. Electronic properties of CdWO{sub 4}: Use of hybrid exchange and correlation functionals

    Energy Technology Data Exchange (ETDEWEB)

    Meena, B. S., E-mail: bsmphysics@gmail.com; Mund, H. S.; Ahuja, B. L. [Department of Physics, University College of Science, M. L. Sukhadia University, Udaipur-313001 (India); Heda, N. L. [Department of Pure and Applied Physics, University of Kota, Kota-324010 (India)

    2016-05-23

    Energy bands, density of states (DOS), Mulliken population (MP) and electron momentum densities (EMDs) of CdWO{sub 4} are presented using hybrid exchange and correlation functionals namely B3LYP, B3PW and PBE0. To validate the present hybrid potentials, theoretical EMDs have been compared with the experimental Compton profile. It is found that LCAO-B3LYP based Compton profile gives a better agreement with experiment than other theoretical profiles. The energy bands and DOS show a wide band gap semiconducting nature of CdWO{sub 4}. The theoretical band gap obtained using B3LYP scheme reconciles well with the available experimental data. In addition, we have also presented the anisotropies in EMDs along [100], [110] and [001] directions and the bonding effects using the MP data.

  5. Construction of exchange-correlation functionals through interpolation between the non-interacting and the strong-correlation limit

    International Nuclear Information System (INIS)

    Zhou, Yongxi; Ernzerhof, Matthias; Bahmann, Hilke

    2015-01-01

    Drawing on the adiabatic connection of density functional theory, exchange-correlation functionals of Kohn-Sham density functional theory are constructed which interpolate between the extreme limits of the electron-electron interaction strength. The first limit is the non-interacting one, where there is only exchange. The second limit is the strong correlated one, characterized as the minimum of the electron-electron repulsion energy. The exchange-correlation energy in the strong-correlation limit is approximated through a model for the exchange-correlation hole that is referred to as nonlocal-radius model [L. O. Wagner and P. Gori-Giorgi, Phys. Rev. A 90, 052512 (2014)]. Using the non-interacting and strong-correlated extremes, various interpolation schemes are presented that yield new approximations to the adiabatic connection and thus to the exchange-correlation energy. Some of them rely on empiricism while others do not. Several of the proposed approximations yield the exact exchange-correlation energy for one-electron systems where local and semi-local approximations often fail badly. Other proposed approximations generalize existing global hybrids by using a fraction of the exchange-correlation energy in the strong-correlation limit to replace an equal fraction of the semi-local approximation to the exchange-correlation energy in the strong-correlation limit. The performance of the proposed approximations is evaluated for molecular atomization energies, total atomic energies, and ionization potentials

  6. Exchange-correlation energies of atoms from efficient density functionals: influence of the electron density

    Science.gov (United States)

    Tao, Jianmin; Ye, Lin-Hui; Duan, Yuhua

    2017-12-01

    The primary goal of Kohn-Sham density functional theory is to evaluate the exchange-correlation contribution to electronic properties. However, the accuracy of a density functional can be affected by the electron density. Here we apply the nonempirical Tao-Mo (TM) semilocal functional to study the influence of the electron density on the exchange and correlation energies of atoms and ions, and compare the results with the commonly used nonempirical semilocal functionals local spin-density approximation (LSDA), Perdew-Burke-Ernzerhof (PBE), Tao-Perdew-Staroverov-Scuseria (TPSS), and hybrid functional PBE0. We find that the spin-restricted Hartree-Fock density yields the exchange and correlation energies in good agreement with the Optimized Effective Potential method, particularly for spherical atoms and ions. However, the errors of these semilocal and hybrid functionals become larger for self-consistent densities. We further find that the quality of the electron density have greater effect on the exchange-correlation energies of kinetic energy density-dependent meta-GGA functionals TPSS and TM than on those of the LSDA and GGA, and therefore, should have greater influence on the performance of meta-GGA functionals. Finally, we show that the influence of the density quality on PBE0 is slightly reduced, compared to that of PBE, due to the exact mixing.

  7. Role of exact exchange in thermally-assisted-occupation density functional theory: A proposal of new hybrid schemes.

    Science.gov (United States)

    Chai, Jeng-Da

    2017-01-28

    We propose hybrid schemes incorporating exact exchange into thermally assisted-occupation-density functional theory (TAO-DFT) [J.-D. Chai, J. Chem. Phys. 136, 154104 (2012)] for an improved description of nonlocal exchange effects. With a few simple modifications, global and range-separated hybrid functionals in Kohn-Sham density functional theory (KS-DFT) can be combined seamlessly with TAO-DFT. In comparison with global hybrid functionals in KS-DFT, the resulting global hybrid functionals in TAO-DFT yield promising performance for systems with strong static correlation effects (e.g., the dissociation of H 2 and N 2 , twisted ethylene, and electronic properties of linear acenes), while maintaining similar performance for systems without strong static correlation effects. Besides, a reasonably accurate description of noncovalent interactions can be efficiently achieved through the inclusion of dispersion corrections in hybrid TAO-DFT. Relative to semilocal density functionals in TAO-DFT, global hybrid functionals in TAO-DFT are generally superior in performance for a wide range of applications, such as thermochemistry, kinetics, reaction energies, and optimized geometries.

  8. Effect of exchange correlation potential on dispersion properties of lower hybrid wave in degenerate plasma

    Science.gov (United States)

    Rimza, Tripti; Sharma, Prerana

    2017-05-01

    The dispersion properties of lower hybrid wave are studied in electron-iondegenerate plasma with exchange effect in non-relativistic regime. It is found that the combined effect of Bohm potential and exchange correlation potential significantly modifies the dispersion properties of lower hybrid wave. The graphical results explicitly show the influence of degeneracy pressure, Bohm force and exchange correlation potential on the frequency of the lower hybrid mode. Present work should be of relevance for the dense astrophysical environments like white dwarfs and for laboratory experiments.

  9. Hybrid functional pseudopotentials

    Science.gov (United States)

    Yang, Jing; Tan, Liang Z.; Rappe, Andrew M.

    2018-02-01

    The consistency between the exchange-correlation functional used in pseudopotential construction and in the actual density functional theory calculation is essential for the accurate prediction of fundamental properties of materials. However, routine hybrid density functional calculations at present still rely on generalized gradient approximation pseudopotentials due to the lack of hybrid functional pseudopotentials. Here, we present a scheme for generating hybrid functional pseudopotentials, and we analyze the importance of pseudopotential density functional consistency for hybrid functionals. For the PBE0 hybrid functional, we benchmark our pseudopotentials for structural parameters and fundamental electronic gaps of the Gaussian-2 (G2) molecular dataset and some simple solids. Our results show that using our PBE0 pseudopotentials in PBE0 calculations improves agreement with respect to all-electron calculations.

  10. Local hybrid functionals: An assessment for thermochemical kinetics

    International Nuclear Information System (INIS)

    Kaupp, Martin; Bahmann, Hilke; Arbuznikov, Alexei V.

    2007-01-01

    Local hybrid functionals with position-dependent exact-exchange admixture are a new class of exchange-correlation functionals in density functional theory that promise to advance the available accuracy in many areas of application. Local hybrids with different local mixing functions (LMFs) governing the position dependence are validated for the heats of formation of the extended G3/99 set, and for two sets of barriers of hydrogen-transfer and heavy-atom transfer reactions (HTBH38 and NHTBH38 databases). A simple local hybrid Lh-SVWN with only Slater and exact exchange plus local correlation and a one-parameter LMF, g(r)=b(τ W (r)/τ(r)), performs best and provides overall mean absolute errors for thermochemistry and kinetics that are a significant improvement over standard state-of-the-art global hybrid functionals. In particular, this local hybrid functional does not suffer from the systematic deterioration that standard functionals exhibit for larger molecules. In contrast, local hybrids based on generalized gradient approximation exchange tend to give rise to nonintuitive LMFs, and no improved functionals have been obtained along this route. The LMF is a real-space function and thus can be analyzed in detail. We use, in particular, graphical analyses to rationalize the performance of different local hybrids for thermochemistry and reaction barriers

  11. A general range-separated double-hybrid density-functional theory.

    Science.gov (United States)

    Kalai, Cairedine; Toulouse, Julien

    2018-04-28

    A range-separated double-hybrid (RSDH) scheme which generalizes the usual range-separated hybrids and double hybrids is developed. This scheme consistently uses a two-parameter Coulomb-attenuating-method (CAM)-like decomposition of the electron-electron interaction for both exchange and correlation in order to combine Hartree-Fock exchange and second-order Møller-Plesset (MP2) correlation with a density functional. The RSDH scheme relies on an exact theory which is presented in some detail. Several semi-local approximations are developed for the short-range exchange-correlation density functional involved in this scheme. After finding optimal values for the two parameters of the CAM-like decomposition, the RSDH scheme is shown to have a relatively small basis dependence and to provide atomization energies, reaction barrier heights, and weak intermolecular interactions globally more accurate or comparable to range-separated MP2 or standard MP2. The RSDH scheme represents a new family of double hybrids with minimal empiricism which could be useful for general chemical applications.

  12. Approximate self-consistent potentials for density-functional-theory exchange-correlation functionals

    International Nuclear Information System (INIS)

    Cafiero, Mauricio; Gonzalez, Carlos

    2005-01-01

    We show that potentials for exchange-correlation functionals within the Kohn-Sham density-functional-theory framework may be written as potentials for simpler functionals multiplied by a factor close to unity, and in a self-consistent field calculation, these effective potentials find the correct self-consistent solutions. This simple theory is demonstrated with self-consistent exchange-only calculations of the atomization energies of some small molecules using the Perdew-Kurth-Zupan-Blaha (PKZB) meta-generalized-gradient-approximation (meta-GGA) exchange functional. The atomization energies obtained with our method agree with or surpass previous meta-GGA calculations performed in a non-self-consistent manner. The results of this work suggest the utility of this simple theory to approximate exchange-correlation potentials corresponding to energy functionals too complicated to generate closed forms for their potentials. We hope that this method will encourage the development of complex functionals which have correct boundary conditions and are free of self-interaction errors without the worry that the functionals are too complex to differentiate to obtain potentials

  13. Correlation functional in screened-exchange density functional theory procedures.

    Science.gov (United States)

    Chan, Bun; Kawashima, Yukio; Hirao, Kimihiko

    2017-10-15

    In the present study, we have explored several prospects for the further development of screened-exchange density functional theory (SX-DFT) procedures. Using the performance of HSE06 as our measure, we find that the use of alternative correlation functionals (as oppose to PBEc in HSE06) also yields adequate results for a diverse set of thermochemical properties. We have further examined the performance of new SX-DFT procedures (termed HSEB-type methods) that comprise the HSEx exchange and a (near-optimal) reparametrized B97c (c OS,0  = c SS,0  = 1, c OS,1  = -1.5, c OS,2  = -0.644, c SS,1  = -0.5, and c SS,2  = 1.10) correlation functionals. The different variants of HSEB all perform comparably to or slightly better than the original HSE-type procedures. These results, together with our fundamental analysis of correlation functionals, point toward various directions for advancing SX-DFT methods. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  14. Assessing the role of Hartree-Fock exchange, correlation energy and long range corrections in evaluating ionization potential, and electron affinity in density functional theory.

    Science.gov (United States)

    Vikramaditya, Talapunur; Lin, Shiang-Tai

    2017-06-05

    Accurate determination of ionization potentials (IPs), electron affinities (EAs), fundamental gaps (FGs), and HOMO, LUMO energy levels of organic molecules play an important role in modeling and predicting the efficiencies of organic photovoltaics, OLEDs etc. In this work, we investigate the effects of Hartree Fock (HF) Exchange, correlation energy, and long range corrections in predicting IP and EA in Hybrid Functionals. We observe increase in percentage of HF exchange results in increase of IPs and decrease in EAs. Contrary to the general expectations inclusion of both HF exchange and correlation energy (from the second order perturbation theory MP2) leads to poor prediction. Range separated Hybrid Functionals are found to be more reliable among various DFT Functionals investigated. DFT Functionals predict accurate IPs whereas post HF methods predict accurate EAs. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  15. Exchange-Correlation Effects for Noncovalent Interactions in Density Functional Theory.

    Science.gov (United States)

    Otero-de-la-Roza, A; DiLabio, Gino A; Johnson, Erin R

    2016-07-12

    In this article, we develop an understanding of how errors from exchange-correlation functionals affect the modeling of noncovalent interactions in dispersion-corrected density-functional theory. Computed CCSD(T) reference binding energies for a collection of small-molecule clusters are decomposed via a molecular many-body expansion and are used to benchmark density-functional approximations, including the effect of semilocal approximation, exact-exchange admixture, and range separation. Three sources of error are identified. Repulsion error arises from the choice of semilocal functional approximation. This error affects intermolecular repulsions and is present in all n-body exchange-repulsion energies with a sign that alternates with the order n of the interaction. Delocalization error is independent of the choice of semilocal functional but does depend on the exact exchange fraction. Delocalization error misrepresents the induction energies, leading to overbinding in all induction n-body terms, and underestimates the electrostatic contribution to the 2-body energies. Deformation error affects only monomer relaxation (deformation) energies and behaves similarly to bond-dissociation energy errors. Delocalization and deformation errors affect systems with significant intermolecular orbital interactions (e.g., hydrogen- and halogen-bonded systems), whereas repulsion error is ubiquitous. Many-body errors from the underlying exchange-correlation functional greatly exceed in general the magnitude of the many-body dispersion energy term. A functional built to accurately model noncovalent interactions must contain a dispersion correction, semilocal exchange, and correlation components that minimize the repulsion error independently and must also incorporate exact exchange in such a way that delocalization error is absent.

  16. Subsystem density functional theory with meta-generalized gradient approximation exchange-correlation functionals.

    Science.gov (United States)

    Śmiga, Szymon; Fabiano, Eduardo; Laricchia, Savio; Constantin, Lucian A; Della Sala, Fabio

    2015-04-21

    We analyze the methodology and the performance of subsystem density functional theory (DFT) with meta-generalized gradient approximation (meta-GGA) exchange-correlation functionals for non-bonded molecular systems. Meta-GGA functionals depend on the Kohn-Sham kinetic energy density (KED), which is not known as an explicit functional of the density. Therefore, they cannot be directly applied in subsystem DFT calculations. We propose a Laplacian-level approximation to the KED which overcomes this limitation and provides a simple and accurate way to apply meta-GGA exchange-correlation functionals in subsystem DFT calculations. The so obtained density and energy errors, with respect to the corresponding supermolecular calculations, are comparable with conventional approaches, depending almost exclusively on the approximations in the non-additive kinetic embedding term. An embedding energy error decomposition explains the accuracy of our method.

  17. Local hybrid functionals with orbital-free mixing functions and balanced elimination of self-interaction error

    International Nuclear Information System (INIS)

    Silva, Piotr de; Corminboeuf, Clémence

    2015-01-01

    The recently introduced density overlap regions indicator (DORI) [P. de Silva and C. Corminboeuf, J. Chem. Theory Comput. 10(9), 3745–3756 (2014)] is a density-dependent scalar field revealing regions of high density overlap between shells, atoms, and molecules. In this work, we exploit its properties to construct local hybrid exchange-correlation functionals aiming at balanced reduction of the self-interaction error. We show that DORI can successfully replace the ratio of the von Weizsäcker and exact positive-definite kinetic energy densities, which is commonly used in mixing functions of local hybrids. Additionally, we introduce several semi-empirical parameters to control the local and global admixture of exact exchange. The most promising of our local hybrids clearly outperforms the underlying semi-local functionals as well as their global hybrids

  18. Orbital-dependent exchange-correlation functionals in density-functional theory realized by the FLAPW method

    Energy Technology Data Exchange (ETDEWEB)

    Betzinger, Markus

    2011-12-14

    In this thesis, we extended the applicability of the full-potential linearized augmented-plane-wave (FLAPW) method, one of the most precise, versatile and generally applicable electronic structure methods for solids working within the framework of density-functional theory (DFT), to orbital-dependent functionals for the exchange-correlation (xc) energy. Two different schemes that deal with orbital-dependent functionals, the Kohn-Sham (KS) and the generalized Kohn-Sham (gKS) formalism, have been realized. Hybrid functionals, combining some amount of the orbital-dependent exact exchange energy with local or semi-local functionals of the density, are implemented within the gKS scheme. We work in particular with the PBE0 hybrid of Perdew, Burke, and Ernzerhof. Our implementation relies on a representation of the non-local exact exchange potential - its calculation constitutes the most time consuming step in a practical calculation - by an auxiliary mixed product basis (MPB). In this way, the matrix elements of the Hamiltonian corresponding to the non-local potential become a Brillouin-zone (BZ) sum over vector-matrix-vector products. Several techniques are developed and explored to further accelerate our numerical scheme. We show PBE0 results for a variety of semiconductors and insulators. In comparison with experiment, the PBE0 functional leads to improved band gaps and an improved description of localized states. Even for the ferromagnetic semiconductor EuO with localized 4f electrons, the electronic and magnetic properties are correctly described by the PBE0 functional. Subsequently, we discuss the construction of the local, multiplicative exact exchange (EXX) potential from the non-local, orbital-dependent exact exchange energy. For this purpose we employ the optimized effective potential (OEP) method. Central ingredients of the OEP equation are the KS wave-function response and the single-particle density response function. We show that a balance between the LAPW

  19. Orbital-dependent exchange-correlation functionals in density-functional theory realized by the FLAPW method

    International Nuclear Information System (INIS)

    Betzinger, Markus

    2011-01-01

    In this thesis, we extended the applicability of the full-potential linearized augmented-plane-wave (FLAPW) method, one of the most precise, versatile and generally applicable electronic structure methods for solids working within the framework of density-functional theory (DFT), to orbital-dependent functionals for the exchange-correlation (xc) energy. Two different schemes that deal with orbital-dependent functionals, the Kohn-Sham (KS) and the generalized Kohn-Sham (gKS) formalism, have been realized. Hybrid functionals, combining some amount of the orbital-dependent exact exchange energy with local or semi-local functionals of the density, are implemented within the gKS scheme. We work in particular with the PBE0 hybrid of Perdew, Burke, and Ernzerhof. Our implementation relies on a representation of the non-local exact exchange potential - its calculation constitutes the most time consuming step in a practical calculation - by an auxiliary mixed product basis (MPB). In this way, the matrix elements of the Hamiltonian corresponding to the non-local potential become a Brillouin-zone (BZ) sum over vector-matrix-vector products. Several techniques are developed and explored to further accelerate our numerical scheme. We show PBE0 results for a variety of semiconductors and insulators. In comparison with experiment, the PBE0 functional leads to improved band gaps and an improved description of localized states. Even for the ferromagnetic semiconductor EuO with localized 4f electrons, the electronic and magnetic properties are correctly described by the PBE0 functional. Subsequently, we discuss the construction of the local, multiplicative exact exchange (EXX) potential from the non-local, orbital-dependent exact exchange energy. For this purpose we employ the optimized effective potential (OEP) method. Central ingredients of the OEP equation are the KS wave-function response and the single-particle density response function. We show that a balance between the LAPW

  20. Effect of the nonlocal exchange on the performance of the orbital-dependent correlation functionals from second-order perturbation theory.

    Science.gov (United States)

    Schweigert, Igor V; Bartlett, Rodney J

    2008-09-28

    Adding a fraction of the nonlocal exchange operator to the local orbital-dependent exchange potential improves the many-body perturbation expansion based on the Kohn-Sham determinant. The effect of such a hybrid scheme on the performance of the orbital-dependent correlation functional from the second-order perturbation theory (PT2H) is investigated numerically. A small fraction of the nonlocal exchange is often sufficient to ensure the existence of the self-consistent solution for the PT2H potential. In the He and Be atoms, including 37% of the nonlocal exchange leads to the correlation energies and electronic densities that are very close to the exact ones. In molecules, varying the fraction of the nonlocal exchange may result in the PT2H energy closely reproducing the CCSD(T) value; however such a fraction depends on the system and does not always result in an accurate electronic density. We also numerically verify that the "semicanonical" perturbation series includes most of the beneficial effects of the nonlocal exchange without sacrificing the locality of the exchange potential.

  1. Screened exchange hybrid density functional for accurate and efficient structures and interaction energies.

    Science.gov (United States)

    Brandenburg, Jan Gerit; Caldeweyher, Eike; Grimme, Stefan

    2016-06-21

    We extend the recently introduced PBEh-3c global hybrid density functional [S. Grimme et al., J. Chem. Phys., 2015, 143, 054107] by a screened Fock exchange variant based on the Henderson-Janesko-Scuseria exchange hole model. While the excellent performance of the global hybrid is maintained for small covalently bound molecules, its performance for computed condensed phase mass densities is further improved. Most importantly, a speed up of 30 to 50% can be achieved and especially for small orbital energy gap cases, the method is numerically much more robust. The latter point is important for many applications, e.g., for metal-organic frameworks, organic semiconductors, or protein structures. This enables an accurate density functional based electronic structure calculation of a full DNA helix structure on a single core desktop computer which is presented as an example in addition to comprehensive benchmark results.

  2. Source-Free Exchange-Correlation Magnetic Fields in Density Functional Theory.

    Science.gov (United States)

    Sharma, S; Gross, E K U; Sanna, A; Dewhurst, J K

    2018-03-13

    Spin-dependent exchange-correlation energy functionals in use today depend on the charge density and the magnetization density: E xc [ρ, m]. However, it is also correct to define the functional in terms of the curl of m for physical external fields: E xc [ρ,∇ × m]. The exchange-correlation magnetic field, B xc , then becomes source-free. We study this variation of the theory by uniquely removing the source term from local and generalized gradient approximations to the functional. By doing so, the total Kohn-Sham moments are improved for a wide range of materials for both functionals. Significantly, the moments for the pnictides are now in good agreement with experiment. This source-free method is simple to implement in all existing density functional theory codes.

  3. Inhomogeneity induced and appropriately parameterized semilocal exchange and correlation energy functionals in two-dimensions

    Science.gov (United States)

    Patra, Abhilash; Jana, Subrata; Samal, Prasanjit

    2018-04-01

    The construction of meta generalized gradient approximations based on the density matrix expansion (DME) is considered as one of the most accurate techniques to design semilocal exchange energy functionals in two-dimensional density functional formalism. The exchange holes modeled using DME possess unique features that make it a superior entity. Parameterized semilocal exchange energy functionals based on the DME are proposed. The use of different forms of the momentum and flexible parameters is to subsume the non-uniform effects of the density in the newly constructed semilocal functionals. In addition to the exchange functionals, a suitable correlation functional is also constructed by working upon the local correlation functional developed for 2D homogeneous electron gas. The non-local effects are induced into the correlation functional by a parametric form of one of the newly constructed exchange energy functionals. The proposed functionals are applied to the parabolic quantum dots with a varying number of confined electrons and the confinement strength. The results obtained with the aforementioned functionals are quite satisfactory, which indicates why these are suitable for two-dimensional quantum systems.

  4. Electronic properties of antiferromagnetic UBi2 metal by exact exchange for correlated electrons method

    Directory of Open Access Journals (Sweden)

    E Ghasemikhah

    2012-03-01

    Full Text Available This study investigated the electronic properties of antiferromagnetic UBi2 metal by using ab initio calculations based on the density functional theory (DFT, employing the augmented plane waves plus local orbital method. We used the exact exchange for correlated electrons (EECE method to calculate the exchange-correlation energy under a variety of hybrid functionals. Electric field gradients (EFGs at the uranium site in UBi2 compound were calculated and compared with the experiment. The EFGs were predicted experimentally at the U site to be very small in this compound. The EFG calculated by the EECE functional are in agreement with the experiment. The densities of states (DOSs show that 5f U orbital is hybrided with the other orbitals. The plotted Fermi surfaces show that there are two kinds of charges on Fermi surface of this compound.

  5. Evaluation of exchange-correlation functionals for time-dependent density functional theory calculations on metal complexes.

    Science.gov (United States)

    Holland, Jason P; Green, Jennifer C

    2010-04-15

    The electronic absorption spectra of a range of copper and zinc complexes have been simulated by using time-dependent density functional theory (TD-DFT) calculations implemented in Gaussian03. In total, 41 exchange-correlation (XC) functionals including first-, second-, and third-generation (meta-generalized gradient approximation) DFT methods were compared in their ability to predict the experimental electronic absorption spectra. Both pure and hybrid DFT methods were tested and differences between restricted and unrestricted calculations were also investigated by comparison of analogous neutral zinc(II) and copper(II) complexes. TD-DFT calculated spectra were optimized with respect to the experimental electronic absorption spectra by use of a Matlab script. Direct comparison of the performance of each XC functional was achieved both qualitatively and quantitatively by comparison of optimized half-band widths, root-mean-squared errors (RMSE), energy scaling factors (epsilon(SF)), and overall quality-of-fit (Q(F)) parameters. Hybrid DFT methods were found to outperform all pure DFT functionals with B1LYP, B97-2, B97-1, X3LYP, and B98 functionals providing the highest quantitative and qualitative accuracy in both restricted and unrestricted systems. Of the functionals tested, B1LYP gave the most accurate results with both average RMSE and overall Q(F) 0.990) for the copper complexes. The XC functional performance in spin-restricted TD-DFT calculations on the zinc complexes was found to be slightly worse. PBE1PBE, mPW1PW91 and B1LYP gave the most accurate results with typical RMSE and Q(F) values between 5.3 and 7.3%, and epsilon(SF) around 0.930. These studies illustrate the power of modern TD-DFT calculations for exploring excited state transitions of metal complexes. 2009 Wiley Periodicals, Inc.

  6. The double-soft limit in cosmological correlation functions and graviton exchange effects

    Energy Technology Data Exchange (ETDEWEB)

    Alinea, Allan L.; Kubota, Takahiro; Misumi, Nobuhiko, E-mail: alinea@het.phys.sci.osaka-u.ac.jp, E-mail: kubota@celas.osaka-u.ac.jp, E-mail: misumi.nobu@gmail.com [Department of Physics, Osaka University, Toyonaka, Osaka 560-0043 (Japan)

    2017-01-01

    The graviton exchange effect on cosmological correlation functions is examined by employing the double-soft limit technique. A new relation among correlation functions that contain the effects due to graviton exchange diagrams in addition to those due to scalar-exchange and scalar-contact-interaction, is derived by using the background field method and independently by the method of Ward identities associated with dilatation symmetry. We compare these three terms, putting small values for the slow-roll parameters and (1− n {sub s} ) ≈ 0.042, where n {sub s} is the scalar spectral index. It is argued that the graviton exchange effects are more dominant than the other two and could be observed in the trispectrum in the double-soft limit. Our observation strengthens the previous work by Seery, Sloth and Vernizzi, in which it has been argued that the graviton exchange dominates in the counter-collinear limit for single field slow-roll inflation.

  7. Derivative discontinuity and exchange-correlation potential of meta-GGAs in density-functional theory.

    Science.gov (United States)

    Eich, F G; Hellgren, Maria

    2014-12-14

    We investigate fundamental properties of meta-generalized-gradient approximations (meta-GGAs) to the exchange-correlation energy functional, which have an implicit density dependence via the Kohn-Sham kinetic-energy density. To this purpose, we construct the most simple meta-GGA by expressing the local exchange-correlation energy per particle as a function of a fictitious density, which is obtained by inverting the Thomas-Fermi kinetic-energy functional. This simple functional considerably improves the total energy of atoms as compared to the standard local density approximation. The corresponding exchange-correlation potentials are then determined exactly through a solution of the optimized effective potential equation. These potentials support an additional bound state and exhibit a derivative discontinuity at integer particle numbers. We further demonstrate that through the kinetic-energy density any meta-GGA incorporates a derivative discontinuity. However, we also find that for commonly used meta-GGAs the discontinuity is largely underestimated and in some cases even negative.

  8. Derivative discontinuity and exchange-correlation potential of meta-GGAs in density-functional theory

    International Nuclear Information System (INIS)

    Eich, F. G.; Hellgren, Maria

    2014-01-01

    We investigate fundamental properties of meta-generalized-gradient approximations (meta-GGAs) to the exchange-correlation energy functional, which have an implicit density dependence via the Kohn-Sham kinetic-energy density. To this purpose, we construct the most simple meta-GGA by expressing the local exchange-correlation energy per particle as a function of a fictitious density, which is obtained by inverting the Thomas-Fermi kinetic-energy functional. This simple functional considerably improves the total energy of atoms as compared to the standard local density approximation. The corresponding exchange-correlation potentials are then determined exactly through a solution of the optimized effective potential equation. These potentials support an additional bound state and exhibit a derivative discontinuity at integer particle numbers. We further demonstrate that through the kinetic-energy density any meta-GGA incorporates a derivative discontinuity. However, we also find that for commonly used meta-GGAs the discontinuity is largely underestimated and in some cases even negative

  9. Increasing the applicability of density functional theory. IV. Consequences of ionization-potential improved exchange-correlation potentials.

    Science.gov (United States)

    Verma, Prakash; Bartlett, Rodney J

    2014-05-14

    This paper's objective is to create a "consistent" mean-field based Kohn-Sham (KS) density functional theory (DFT) meaning the functional should not only provide good total energy properties, but also the corresponding KS eigenvalues should be accurate approximations to the vertical ionization potentials (VIPs) of the molecule, as the latter condition attests to the viability of the exchange-correlation potential (VXC). None of the prominently used DFT approaches show these properties: the optimized effective potential VXC based ab initio dft does. A local, range-separated hybrid potential cam-QTP-00 is introduced as the basis for a "consistent" KS DFT approach. The computed VIPs as the negative of KS eigenvalue have a mean absolute error of 0.8 eV for an extensive set of molecule's electron ionizations, including the core. Barrier heights, equilibrium geometries, and magnetic properties obtained from the potential are in good agreement with experiment. A similar accuracy with less computational efforts can be achieved by using a non-variational global hybrid variant of the QTP-00 approach.

  10. On the accuracy of density-functional theory exchange-correlation functionals for H bonds in small water clusters: Benchmarks approaching the complete basis set limit

    Science.gov (United States)

    Santra, Biswajit; Michaelides, Angelos; Scheffler, Matthias

    2007-11-01

    The ability of several density-functional theory (DFT) exchange-correlation functionals to describe hydrogen bonds in small water clusters (dimer to pentamer) in their global minimum energy structures is evaluated with reference to second order Møller-Plesset perturbation theory (MP2). Errors from basis set incompleteness have been minimized in both the MP2 reference data and the DFT calculations, thus enabling a consistent systematic evaluation of the true performance of the tested functionals. Among all the functionals considered, the hybrid X3LYP and PBE0 functionals offer the best performance and among the nonhybrid generalized gradient approximation functionals, mPWLYP and PBE1W perform best. The popular BLYP and B3LYP functionals consistently underbind and PBE and PW91 display rather variable performance with cluster size.

  11. Non-local exchange correlation functionals impact on the structural, electronic and optical properties of III-V arsenides

    KAUST Repository

    Anua, N. Najwa

    2013-08-20

    Exchange correlation (XC) energy functionals play a vital role in the efficiency of density functional theory (DFT) calculations, more soundly in the calculation of fundamental electronic energy bandgap. In the present DFT study of III-arsenides, we investigate the implications of XC-energy functional and corresponding potential on the structural, electronic and optical properties of XAs (X = B, Al, Ga, In). Firstly we report and discuss the optimized structural lattice parameters and the band gap calculations performed within different non-local XC functionals as implemented in the DFT-packages: WIEN2k, CASTEP and SIESTA. These packages are representative of the available code in ab initio studies. We employed the LDA, GGA-PBE, GGA-WC and mBJ-LDA using WIEN2k. In CASTEP, we employed the hybrid functional, sX-LDA. Furthermore LDA, GGA-PBE and meta-GGA were employed using SIESTA code. Our results point to GGA-WC as a more appropriate approximation for the calculations of structural parameters. However our electronic bandstructure calculations at the level of mBJ-LDA potential show considerable improvements over the other XC functionals, even the sX-LDA hybrid functional. We report also the optical properties within mBJ potential, which show a nice agreement with the experimental measurements in addition to other theoretical results. © 2013 IOP Publishing Ltd.

  12. Magnetic exchange in {Gd(III)-radical} complexes: method assessment, mechanism of coupling and magneto-structural correlations.

    Science.gov (United States)

    Gupta, Tulika; Rajeshkumar, Thayalan; Rajaraman, Gopalan

    2014-07-28

    Density functional studies have been performed on ten different {Gd(III)-radical} complexes exhibiting both ferro and antiferromagnetic exchange interaction with an aim to assess a suitable exchange-correlation functional within DFT formalism. This study has also been extended to probe the mechanism of magnetic coupling and to develop suitable magneto-structural correlations for this pair. Our method assessments reveal the following order of increasing accuracy for the evaluation of J values compared to experimental coupling constants: B(40HF)LYP X3LYP < B3LYP < B2PLYP. Grimme's double-hybrid functional is found to be superior compared to other functionals tested and this is followed very closely by the conventional hybrid B3LYP functional. At the basis set front, our calculations reveal that the incorporation of relativistic effect is important in these calculations and the relativistically corrected effective core potential (ECP) basis set is found to yield better Js compared to other methods. The supposedly empty 5d/6s/6p orbitals of Gd(III) are found to play an important role in the mechanism of magnetic coupling and different contributions to the exchange terms are probed using Molecular Orbital (MO) and Natural Bond Orbital (NBO) analysis. Magneto-structural correlations for Gd-O distances, Gd-O-N angles and Gd-O-N-C dihedral angles are developed where the bond angles as well as dihedral angle parameters are found to dictate the sign and strength of the magnetic coupling in this series.

  13. Efficient construction of exchange and correlation potentials by inverting the Kohn-Sham equations.

    Science.gov (United States)

    Kananenka, Alexei A; Kohut, Sviataslau V; Gaiduk, Alex P; Ryabinkin, Ilya G; Staroverov, Viktor N

    2013-08-21

    Given a set of canonical Kohn-Sham orbitals, orbital energies, and an external potential for a many-electron system, one can invert the Kohn-Sham equations in a single step to obtain the corresponding exchange-correlation potential, vXC(r). For orbitals and orbital energies that are solutions of the Kohn-Sham equations with a multiplicative vXC(r) this procedure recovers vXC(r) (in the basis set limit), but for eigenfunctions of a non-multiplicative one-electron operator it produces an orbital-averaged potential. In particular, substitution of Hartree-Fock orbitals and eigenvalues into the Kohn-Sham inversion formula is a fast way to compute the Slater potential. In the same way, we efficiently construct orbital-averaged exchange and correlation potentials for hybrid and kinetic-energy-density-dependent functionals. We also show how the Kohn-Sham inversion approach can be used to compute functional derivatives of explicit density functionals and to approximate functional derivatives of orbital-dependent functionals.

  14. Combined hybrid functional and DFT+U calculations for metal chalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Aras, Mehmet; Kılıç, Çetin, E-mail: cetin-kilic@gyte.edu.tr [Department of Physics, Gebze Institute of Technology, Gebze, Kocaeli 41400 (Turkey)

    2014-07-28

    In the density-functional studies of materials with localized electronic states, the local/semilocal exchange-correlation functionals are often either combined with a Hubbard parameter U as in the LDA+U method or mixed with a fraction of exactly computed (Fock) exchange energy yielding a hybrid functional. Although some inaccuracies of the semilocal density approximations are thus fixed to a certain extent, the improvements are not sufficient to make the predictions agree with the experimental data. Here, we put forward the perspective that the hybrid functional scheme and the LDA+U method should be treated as complementary, and propose to combine the range-separated Heyd-Scuseria-Ernzerhof (HSE) hybrid functional with the Hubbard U. We thus present a variety of HSE+U calculations for a set of II-VI semiconductors, consisting of zinc and cadmium monochalcogenides, along with comparison to the experimental data. Our findings imply that an optimal value U{sup *} of the Hubbard parameter could be determined, which ensures that the HSE+U{sup *} calculation reproduces the experimental band gap. It is shown that an improved description not only of the electronic structure but also of the crystal structure and energetics is obtained by adding the U{sup *} term to the HSE functional, proving the utility of HSE+U{sup *} approach in modeling semiconductors with localized electronic states.

  15. On the accuracy of van der Waals inclusive density-functional theory exchange-correlation functionals for ice at ambient and high pressures.

    Science.gov (United States)

    Santra, Biswajit; Klimes, Jirí; Tkatchenko, Alexandre; Alfè, Dario; Slater, Ben; Michaelides, Angelos; Car, Roberto; Scheffler, Matthias

    2013-10-21

    Density-functional theory (DFT) has been widely used to study water and ice for at least 20 years. However, the reliability of different DFT exchange-correlation (xc) functionals for water remains a matter of considerable debate. This is particularly true in light of the recent development of DFT based methods that account for van der Waals (vdW) dispersion forces. Here, we report a detailed study with several xc functionals (semi-local, hybrid, and vdW inclusive approaches) on ice Ih and six proton ordered phases of ice. Consistent with our previous study [B. Santra, J. Klimeš, D. Alfè, A. Tkatchenko, B. Slater, A. Michaelides, R. Car, and M. Scheffler, Phys. Rev. Lett. 107, 185701 (2011)] which showed that vdW forces become increasingly important at high pressures, we find here that all vdW inclusive methods considered improve the relative energies and transition pressures of the high-pressure ice phases compared to those obtained with semi-local or hybrid xc functionals. However, we also find that significant discrepancies between experiment and the vdW inclusive approaches remain in the cohesive properties of the various phases, causing certain phases to be absent from the phase diagram. Therefore, room for improvement in the description of water at ambient and high pressures remains and we suggest that because of the stern test the high pressure ice phases pose they should be used in future benchmark studies of simulation methods for water.

  16. An efficient method for hybrid density functional calculation with spin-orbit coupling

    Science.gov (United States)

    Wang, Maoyuan; Liu, Gui-Bin; Guo, Hong; Yao, Yugui

    2018-03-01

    In first-principles calculations, hybrid functional is often used to improve accuracy from local exchange correlation functionals. A drawback is that evaluating the hybrid functional needs significantly more computing effort. When spin-orbit coupling (SOC) is taken into account, the non-collinear spin structure increases computing effort by at least eight times. As a result, hybrid functional calculations with SOC are intractable in most cases. In this paper, we present an approximate solution to this problem by developing an efficient method based on a mixed linear combination of atomic orbital (LCAO) scheme. We demonstrate the power of this method using several examples and we show that the results compare very well with those of direct hybrid functional calculations with SOC, yet the method only requires a computing effort similar to that without SOC. The presented technique provides a good balance between computing efficiency and accuracy, and it can be extended to magnetic materials.

  17. Accurate orbital-dependent correlation and exchange-correlation potentials from non-iterative ab initio dft calculations

    Science.gov (United States)

    Grabowski, Ireneusz; Lotrich, Victor

    2005-08-01

    A new approximate non-iterative procedure to obtain accurate correlation and exchange-correlation potentials of Kohn-Sham (KS) density functional theory (DFT) is presented. By carrying out only one step of the correlated optimized effective potential (OEP) iterations following the standard iterative exchange-only OEP, one can recover accurate correlation potentials corresponding to the orbital-dependent second-order many-body perturbation theory [MBPT(2)] energy functional that are hardly discernible from those obtained by the more expensive, fully iterative procedure. This new 'one-step' OEP-MBPT(2) algorithm reflects the non-iterative, perturbative algorithm of standard, canonical MBPT(2) of ab initio wave function theory, while it allows the correlation potentials to readjust and include the majority of the MBPT(2) correlation effect. It is also flexible in the treatment of exchange and the Hartree-Fock orbitals may be used in lieu of the exchange-only OEP orbitals, when the correlation or exchange-correlation potential is of interest.

  18. MN15-L: A New Local Exchange-Correlation Functional for Kohn-Sham Density Functional Theory with Broad Accuracy for Atoms, Molecules, and Solids.

    Science.gov (United States)

    Yu, Haoyu S; He, Xiao; Truhlar, Donald G

    2016-03-08

    Kohn-Sham density functional theory is widely used for applications of electronic structure theory in chemistry, materials science, and condensed-matter physics, but the accuracy depends on the quality of the exchange-correlation functional. Here, we present a new local exchange-correlation functional called MN15-L that predicts accurate results for a broad range of molecular and solid-state properties including main-group bond energies, transition metal bond energies, reaction barrier heights, noncovalent interactions, atomic excitation energies, ionization potentials, electron affinities, total atomic energies, hydrocarbon thermochemistry, and lattice constants of solids. The MN15-L functional has the same mathematical form as a previous meta-nonseparable gradient approximation exchange-correlation functional, MN12-L, but it is improved because we optimized it against a larger database, designated 2015A, and included smoothness restraints; the optimization has a much better representation of transition metals. The mean unsigned error on 422 chemical energies is 2.32 kcal/mol, which is the best among all tested functionals, with or without nonlocal exchange. The MN15-L functional also provides good results for test sets that are outside the training set. A key issue is that the functional is local (no nonlocal exchange or nonlocal correlation), which makes it relatively economical for treating large and complex systems and solids. Another key advantage is that medium-range correlation energy is built in so that one does not need to add damped dispersion by molecular mechanics in order to predict accurate noncovalent binding energies. We believe that the MN15-L functional should be useful for a wide variety of applications in chemistry, physics, materials science, and molecular biology.

  19. Global hybrids from the semiclassical atom theory satisfying the local density linear response.

    Science.gov (United States)

    Fabiano, Eduardo; Constantin, Lucian A; Cortona, Pietro; Della Sala, Fabio

    2015-01-13

    We propose global hybrid approximations of the exchange-correlation (XC) energy functional which reproduce well the modified fourth-order gradient expansion of the exchange energy in the semiclassical limit of many-electron neutral atoms and recover the full local density approximation (LDA) linear response. These XC functionals represent the hybrid versions of the APBE functional [Phys. Rev. Lett. 2011, 106, 186406] yet employing an additional correlation functional which uses the localization concept of the correlation energy density to improve the compatibility with the Hartree-Fock exchange as well as the coupling-constant-resolved XC potential energy. Broad energetic and structural testing, including thermochemistry and geometry, transition metal complexes, noncovalent interactions, gold clusters and small gold-molecule interfaces, as well as an analysis of the hybrid parameters, show that our construction is quite robust. In particular, our testing shows that the resulting hybrid, including 20% of Hartree-Fock exchange and named hAPBE, performs remarkably well for a broad palette of systems and properties, being generally better than popular hybrids (PBE0 and B3LYP). Semiempirical dispersion corrections are also provided.

  20. Performance of exchange-correlation functionals in density functional theory calculations for liquid metal: A benchmark test for sodium

    Science.gov (United States)

    Han, Jeong-Hwan; Oda, Takuji

    2018-04-01

    The performance of exchange-correlation functionals in density-functional theory (DFT) calculations for liquid metal has not been sufficiently examined. In the present study, benchmark tests of Perdew-Burke-Ernzerhof (PBE), Armiento-Mattsson 2005 (AM05), PBE re-parameterized for solids, and local density approximation (LDA) functionals are conducted for liquid sodium. The pair correlation function, equilibrium atomic volume, bulk modulus, and relative enthalpy are evaluated at 600 K and 1000 K. Compared with the available experimental data, the errors range from -11.2% to 0.0% for the atomic volume, from -5.2% to 22.0% for the bulk modulus, and from -3.5% to 2.5% for the relative enthalpy depending on the DFT functional. The generalized gradient approximation functionals are superior to the LDA functional, and the PBE and AM05 functionals exhibit the best performance. In addition, we assess whether the error tendency in liquid simulations is comparable to that in solid simulations, which would suggest that the atomic volume and relative enthalpy performances are comparable between solid and liquid states but that the bulk modulus performance is not. These benchmark test results indicate that the results of liquid simulations are significantly dependent on the exchange-correlation functional and that the DFT functional performance in solid simulations can be used to roughly estimate the performance in liquid simulations.

  1. Water on BN doped benzene: A hard test for exchange-correlation functionals and the impact of exact exchange on weak binding

    International Nuclear Information System (INIS)

    Al-Hamdani, Yasmine S.; Michaelides, Angelos; Alfè, Dario; Lilienfeld, O. Anatole von

    2014-01-01

    Density functional theory (DFT) studies of weakly interacting complexes have recently focused on the importance of van der Waals dispersion forces, whereas the role of exchange has received far less attention. Here, by exploiting the subtle binding between water and a boron and nitrogen doped benzene derivative (1,2-azaborine) we show how exact exchange can alter the binding conformation within a complex. Benchmark values have been calculated for three orientations of the water monomer on 1,2-azaborine from explicitly correlated quantum chemical methods, and we have also used diffusion quantum Monte Carlo. For a host of popular DFT exchange-correlation functionals we show that the lack of exact exchange leads to the wrong lowest energy orientation of water on 1,2-azaborine. As such, we suggest that a high proportion of exact exchange and the associated improvement in the electronic structure could be needed for the accurate prediction of physisorption sites on doped surfaces and in complex organic molecules. Meanwhile to predict correct absolute interaction energies an accurate description of exchange needs to be augmented by dispersion inclusive functionals, and certain non-local van der Waals functionals (optB88- and optB86b-vdW) perform very well for absolute interaction energies. Through a comparison with water on benzene and borazine (B 3 N 3 H 6 ) we show that these results could have implications for the interaction of water with doped graphene surfaces, and suggest a possible way of tuning the interaction energy

  2. Development of gradient-corrected exchange-correlation functionals in the density functional theory; Developpement de fonctionnelles corrigees du gradient en theorie de la fonctionnelle de la densite

    Energy Technology Data Exchange (ETDEWEB)

    Lembarki, A.

    1994-12-01

    In this work, we have developed some gradient-corrected exchange-correlation functionals. This study is in keeping with the density functional theory (DFT) formalism. In the first part of this memory, a description of Hartree-Fock (HF), post-HF and density functional theories is given. The second part is devoted the study the different approximations of DFT exchange-correlation functionals which have been proposed in the last years. In particular, we have underlined the approximations used for the construction of these functionals. The third part of this memory consists in the development of new gradient-corrected functionals. In this study, we have established a new relation between exchange energy, correlation energy and kinetic energy. We have deduced two new possible forms of exchange or correlation functionals, respectively. In the fourth part, we have studied the exchange potential, for which the actual formulation does not satisfy some theoretical conditions, such as the asymptotic behavior -1/r. Our contribution lies in the development of an exchange potential with a correct asymptotic -1/r behavior for large values of r. In this chapter, we have proposed a model which permits the obtention of the exchange energy from the exchange potential, using the virial theorem. The fifth part of this memory is devoted the application of these different functionals to simple systems (H{sub 2}O, CO, N{sub 2}O, H{sub 3}{sup +} and H{sub 5}{sup +}) in order to characterize the performance of DFT calculations in regards to those obtained with post-HF methods. (author). 215 refs., 8 figs., 28 tabs.

  3. Density functionals for surface science: Exchange-correlation model development with Bayesian error estimation

    DEFF Research Database (Denmark)

    Wellendorff, Jess; Lundgård, Keld Troen; Møgelhøj, Andreas

    2012-01-01

    A methodology for semiempirical density functional optimization, using regularization and cross-validation methods from machine learning, is developed. We demonstrate that such methods enable well-behaved exchange-correlation approximations in very flexible model spaces, thus avoiding the overfit......A methodology for semiempirical density functional optimization, using regularization and cross-validation methods from machine learning, is developed. We demonstrate that such methods enable well-behaved exchange-correlation approximations in very flexible model spaces, thus avoiding...... the energetics of intramolecular and intermolecular, bulk solid, and surface chemical bonding, and the developed optimization method explicitly handles making the compromise based on the directions in model space favored by different materials properties. The approach is applied to designing the Bayesian error...... sets validates the applicability of BEEF-vdW to studies in chemistry and condensed matter physics. Applications of the approximation and its Bayesian ensemble error estimate to two intricate surface science problems support this....

  4. Exchange coupling in hybrid anisotropy magnetic multilayers quantified by vector magnetometry

    Energy Technology Data Exchange (ETDEWEB)

    Morrison, C., E-mail: C.Morrison.2@warwick.ac.uk; Miles, J. J.; Thomson, T. [School of Computer Science, University of Manchester, Manchester M13 9PL (United Kingdom); Anh Nguyen, T. N. [Materials Physics, School of ICT, KTH Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); Spintronics Research Group, Laboratory for Nanotechnology (LNT), VNU-HCM, Ho Chi Minh City (Viet Nam); Fang, Y.; Dumas, R. K. [Department of Physics, University of Gothenburg, 412 96 Gothenburg (Sweden); Åkerman, J. [Materials Physics, School of ICT, KTH Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); Department of Physics, University of Gothenburg, 412 96 Gothenburg (Sweden)

    2015-05-07

    Hybrid anisotropy thin film heterostructures, where layers with perpendicular and in-plane anisotropy are separated by a thin spacer, are novel materials for zero/low field spin torque oscillators and bit patterned media. Here, we report on magnetization reversal and exchange coupling in a archetypal Co/Pd (perpendicular)-NiFe (in-plane) hybrid anisotropy system studied using vector vibrating sample magnetometry. This technique allows us to quantify the magnetization reversal in each individual magnetic layer, and measure of the interlayer exchange as a function of non-magnetic spacer thickness. At large (>1 nm) spacer thicknesses Ruderman-Kittel-Kasuya-Yosida-like exchange dominates, with orange-peel coupling providing a significant contribution only for sub-nm spacer thickness.

  5. Relativistic Adiabatic Time-Dependent Density Functional Theory Using Hybrid Functionals and Noncollinear Spin Magnetization

    DEFF Research Database (Denmark)

    Bast, Radovan; Jensen, Hans Jørgen Aagaard; Saue, Trond

    2009-01-01

    into reduction of algebra from quaternion to complex or real. For hybrid GGAs with noncollinear spin magnetization we derive a new computationally advantageous equation for the full second variational derivatives of such exchange-correlation functionals. We apply our implementation to calculations on the ns2...... → ns1np1 excitation energies in the Zn, Cd, and Hg atoms (n = 4-6) and (vertical) excitation energies of UO2+ 2 ; and we test the performance of various functionals by comparison with experimental data (group 12 atoms) or higher-level computational results (UO2+2 ). The results indicate...

  6. Phase correlation of foreign exchange time series

    Science.gov (United States)

    Wu, Ming-Chya

    2007-03-01

    Correlation of foreign exchange rates in currency markets is investigated based on the empirical data of USD/DEM and USD/JPY exchange rates for a period from February 1 1986 to December 31 1996. The return of exchange time series is first decomposed into a number of intrinsic mode functions (IMFs) by the empirical mode decomposition method. The instantaneous phases of the resultant IMFs calculated by the Hilbert transform are then used to characterize the behaviors of pricing transmissions, and the correlation is probed by measuring the phase differences between two IMFs in the same order. From the distribution of phase differences, our results show explicitly that the correlations are stronger in daily time scale than in longer time scales. The demonstration for the correlations in periods of 1986-1989 and 1990-1993 indicates two exchange rates in the former period were more correlated than in the latter period. The result is consistent with the observations from the cross-correlation calculation.

  7. Communication: Near-locality of exchange and correlation density functionals for 1- and 2-electron systems

    Science.gov (United States)

    Sun, Jianwei; Perdew, John P.; Yang, Zenghui; Peng, Haowei

    2016-05-01

    The uniform electron gas and the hydrogen atom play fundamental roles in condensed matter physics and quantum chemistry. The former has an infinite number of electrons uniformly distributed over the neutralizing positively charged background, and the latter only one electron bound to the proton. The uniform electron gas was used to derive the local spin density approximation to the exchange-correlation functional that undergirds the development of the Kohn-Sham density functional theory. We show here that the ground-state exchange-correlation energies of the hydrogen atom and many other 1- and 2-electron systems are modeled surprisingly well by a different local spin density approximation (LSDA0). LSDA0 is constructed to satisfy exact constraints but agrees surprisingly well with the exact results for a uniform two-electron density in a finite, curved three-dimensional space. We also apply LSDA0 to excited or noded 1-electron densities, where it works less well. Furthermore, we show that the localization of the exact exchange hole for a 1- or 2-electron ground state can be measured by the ratio of the exact exchange energy to its optimal lower bound.

  8. Communication: Near-locality of exchange and correlation density functionals for 1- and 2-electron systems

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Jianwei; Yang, Zenghui; Peng, Haowei [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States); Perdew, John P. [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States); Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122 (United States)

    2016-05-21

    The uniform electron gas and the hydrogen atom play fundamental roles in condensed matter physics and quantum chemistry. The former has an infinite number of electrons uniformly distributed over the neutralizing positively charged background, and the latter only one electron bound to the proton. The uniform electron gas was used to derive the local spin density approximation to the exchange-correlation functional that undergirds the development of the Kohn-Sham density functional theory. We show here that the ground-state exchange-correlation energies of the hydrogen atom and many other 1- and 2-electron systems are modeled surprisingly well by a different local spin density approximation (LSDA0). LSDA0 is constructed to satisfy exact constraints but agrees surprisingly well with the exact results for a uniform two-electron density in a finite, curved three-dimensional space. We also apply LSDA0 to excited or noded 1-electron densities, where it works less well. Furthermore, we show that the localization of the exact exchange hole for a 1- or 2-electron ground state can be measured by the ratio of the exact exchange energy to its optimal lower bound.

  9. Communication: Near-locality of exchange and correlation density functionals for 1- and 2-electron systems

    International Nuclear Information System (INIS)

    Sun, Jianwei; Yang, Zenghui; Peng, Haowei; Perdew, John P.

    2016-01-01

    The uniform electron gas and the hydrogen atom play fundamental roles in condensed matter physics and quantum chemistry. The former has an infinite number of electrons uniformly distributed over the neutralizing positively charged background, and the latter only one electron bound to the proton. The uniform electron gas was used to derive the local spin density approximation to the exchange-correlation functional that undergirds the development of the Kohn-Sham density functional theory. We show here that the ground-state exchange-correlation energies of the hydrogen atom and many other 1- and 2-electron systems are modeled surprisingly well by a different local spin density approximation (LSDA0). LSDA0 is constructed to satisfy exact constraints but agrees surprisingly well with the exact results for a uniform two-electron density in a finite, curved three-dimensional space. We also apply LSDA0 to excited or noded 1-electron densities, where it works less well. Furthermore, we show that the localization of the exact exchange hole for a 1- or 2-electron ground state can be measured by the ratio of the exact exchange energy to its optimal lower bound.

  10. Towards a Density Functional Theory Exchange-Correlation Functional able to describe localization/delocalization

    Science.gov (United States)

    Mattsson, Ann E.; Wills, John M.

    2013-03-01

    The inability to computationally describe the physics governing the properties of actinides and their alloys is the poster child of failure of existing Density Functional Theory exchange-correlation functionals. The intricate competition between localization and delocalization of the electrons, present in these materials, exposes the limitations of functionals only designed to properly describe one or the other situation. We will discuss the manifestation of this competition in real materials and propositions on how to construct a functional able to accurately describe properties of these materials. I addition we will discuss both the importance of using the Dirac equation to describe the relativistic effects in these materials, and the connection to the physics of transition metal oxides. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  11. Analytic derivatives for perturbatively corrected ''double hybrid'' density functionals: Theory, implementation, and applications

    International Nuclear Information System (INIS)

    Neese, Frank; Schwabe, Tobias; Grimme, Stefan

    2007-01-01

    A recently proposed new family of density functionals [S. Grimme, J. Chem. Phys. 124, 34108 (2006)] adds a fraction of nonlocal correlation as a new ingredient to density functional theory (DFT). This fractional correlation energy is calculated at the level of second-order many-body perturbation theory (PT2) and replaces some of the semilocal DFT correlation of standard hybrid DFT methods. The new ''double hybrid'' functionals (termed, e.g., B2-PLYP) contain only two empirical parameters that have been adjusted in thermochemical calculations on parts of the G2/3 benchmark set. The methods have provided the lowest errors ever obtained by any DFT method for the full G3 set of molecules. In this work, the applicability of the new functionals is extended to the exploration of potential energy surfaces with analytic gradients. The theory of the analytic gradient largely follows the standard theory of PT2 gradients with some additional subtleties due to the presence of the exchange-correlation terms in the self-consistent field operator. An implementation is reported for closed-shell as well as spin-unrestricted reference determinants. Furthermore, the implementation includes external point charge fields and also accommodates continuum solvation models at the level of the conductor like screening model. The density fitting resolution of the identity (RI) approximation can be applied to the evaluation of the PT2 part with large gains in computational efficiency. For systems with ∼500-600 basis functions the evaluation of the double hybrid gradient is approximately four times more expensive than the calculation of the standard hybrid DFT gradient. Extensive test calculations are provided for main group elements and transition metal containing species. The results reveal that the B2-PLYP functional provides excellent molecular geometries that are superior compared to those from standard DFT and MP2

  12. The screening effects of the screened exchange hybrid functional in surface systems: A case study on the CO/Pt(111) problem

    Energy Technology Data Exchange (ETDEWEB)

    Li, H., E-mail: li-huanglong@mail.tsinghua.edu.cn [Department of Precision Instrument, Tsinghua University, Beijing, 100084 (China); Gillen, R. [Institut für Festkörperphysik. Technische Universität Berlin. Hardenbergstr. 36, 10623 Berlin (Germany); Robertson, J., E-mail: jr214@cam.ac.uk [Engineering Department, University of Cambridge, Cambridge CB2 1PZ (United Kingdom)

    2016-06-15

    The screened exchange (sX) hybrid functional has been widely used in computational material science. Although it has widely been studied in bulk systems, less is known about its functional behavior in surface systems which are crucial to many technologies such as materials synthesis and nano-electronic devices. Assessing the screening dependent functional behaviors in the surface systems is therefore important for its application in such systems. In this work, we investigate the screening effects of the sX in CO adsorption on Pt(111) surface. The differences between the sX and Heyd-Scuseria-Ernzerhof (HSE06) hybrid functionals, and the effects of screening parameters are studied. The screening has two effects: first, the HOMO-LUMO gap is screening dependent. This affects the site preference most significantly. In this work, atop adsorption of CO/Pt(111) is predicted by the hybrid functionals with screened exchange potential. The sX(1.44) gives the largest HOMO-LUMO gap for the isolated CO molecule. The adsorption energy difference between the atop and fcc site is also the largest by the sX(1.44) which is explained by the reduced metal d states to the CO 2π* state back-donation, with stronger effect for the fcc adsorption than for the atop adsorption; second, the adsorption energy is screening dependent. This can be seen by comparing the sX(2.38) and HSE06 which have different screening strengths. They show similar surface band structures for the CO adsorption but different adsorption energies, which is explained by the stronger CO 5σ state to the metal d states donation or the effectively screened Pauli repulsion. This work underlines the screening strength as a main difference between sX and HSE06, as well as an important hybrid functional parameter for surface calculation.

  13. Deorbitalization strategies for meta-generalized-gradient-approximation exchange-correlation functionals

    Science.gov (United States)

    Mejia-Rodriguez, Daniel; Trickey, S. B.

    2017-11-01

    We explore the simplification of widely used meta-generalized-gradient approximation (mGGA) exchange-correlation functionals to the Laplacian level of refinement by use of approximate kinetic-energy density functionals (KEDFs). Such deorbitalization is motivated by the prospect of reducing computational cost while recovering a strictly Kohn-Sham local potential framework (rather than the usual generalized Kohn-Sham treatment of mGGAs). A KEDF that has been rather successful in solid simulations proves to be inadequate for deorbitalization, but we produce other forms which, with parametrization to Kohn-Sham results (not experimental data) on a small training set, yield rather good results on standard molecular test sets when used to deorbitalize the meta-GGA made very simple, Tao-Perdew-Staroverov-Scuseria, and strongly constrained and appropriately normed functionals. We also study the difference between high-fidelity and best-performing deorbitalizations and discuss possible implications for use in ab initio molecular dynamics simulations of complicated condensed phase systems.

  14. Molecular Excitation Energies from Time-Dependent Density Functional Theory Employing Random-Phase Approximation Hessians with Exact Exchange.

    Science.gov (United States)

    Heßelmann, Andreas

    2015-04-14

    Molecular excitation energies have been calculated with time-dependent density-functional theory (TDDFT) using random-phase approximation Hessians augmented with exact exchange contributions in various orders. It has been observed that this approach yields fairly accurate local valence excitations if combined with accurate asymptotically corrected exchange-correlation potentials used in the ground-state Kohn-Sham calculations. The inclusion of long-range particle-particle with hole-hole interactions in the kernel leads to errors of 0.14 eV only for the lowest excitations of a selection of three alkene, three carbonyl, and five azabenzene molecules, thus surpassing the accuracy of a number of common TDDFT and even some wave function correlation methods. In the case of long-range charge-transfer excitations, the method typically underestimates accurate reference excitation energies by 8% on average, which is better than with standard hybrid-GGA functionals but worse compared to range-separated functional approximations.

  15. Exact time-dependent exchange-correlation potentials for strong-field electron dynamics

    International Nuclear Information System (INIS)

    Lein, Manfred; Kuemmel, Stephan

    2005-01-01

    By solving the time-dependent Schroedinger equation and inverting the time-dependent Kohn-Sham scheme we obtain the exact time-dependent exchange-correlation potential of density-functional theory for the strong-field dynamics of a correlated system. We demonstrate that essential features of the exact exchange-correlation potential can be related to derivative discontinuities in stationary density-functional theory. Incorporating the discontinuity in a time-dependent density-functional calculation greatly improves the description of the ionization process

  16. Long-range p-d exchange interaction in a ferromagnet-semiconductor hybrid structure

    Science.gov (United States)

    Korenev, V. L.; Salewski, M.; Akimov, I. A.; Sapega, V. F.; Langer, L.; Kalitukha, I. V.; Debus, J.; Dzhioev, R. I.; Yakovlev, D. R.; Müller, D.; Schröder, C.; Hövel, H.; Karczewski, G.; Wiater, M.; Wojtowicz, T.; Kusrayev, Yu. G.; Bayer, M.

    2016-01-01

    Hybrid structures synthesized from different materials have attracted considerable attention because they may allow not only combination of the functionalities of the individual constituents but also mutual control of their properties. To obtain such a control an interaction between the components needs to be established. For coupling the magnetic properties, an exchange interaction has to be implemented which typically depends on wavefunction overlap and is therefore short-ranged, so that it may be compromised across the hybrid interface. Here we study a hybrid structure consisting of a ferromagnetic Co layer and a semiconducting CdTe quantum well, separated by a thin (Cd, Mg)Te barrier. In contrast to the expected p-d exchange that decreases exponentially with the wavefunction overlap of quantum well holes and magnetic atoms, we find a long-ranged, robust coupling that does not vary with barrier width up to more than 30 nm. We suggest that the resulting spin polarization of acceptor-bound holes is induced by an effective p-d exchange that is mediated by elliptically polarized phonons.

  17. Electronic structure of a striped nickelate studied by the exact exchange for correlated electrons (EECE) approach

    KAUST Repository

    Schwingenschlögl, Udo

    2009-12-01

    Motivated by a RIXS study of Wakimoto, et al.(Phys. Rev. Lett., 102 (2009) 157001) we use density functional theory to analyze the magnetic order in the nickelate La5/3Sr1/3NiO4 and the details of its crystal and electronic structure. We compare the generalized gradient approximation to the hybrid functional approach of exact exchange for correlated electrons (EECE). In contrast to the former, the latter reproduces the insulating state of the compound and the midgap states. The EECE approach, in general, appears to be appropriate for describing stripe phases in systems with orbital degrees of freedom. Copyright © EPLA, 2009.

  18. Influence of molecular geometry, exchange-correlation functional, and solvent effects in the modeling of vertical excitation energies in phthalocyanines using time-dependent density functional theory (TDDFT) and polarized continuum model TDDFT methods: can modern computational chemistry methods explain experimental controversies?

    Science.gov (United States)

    Nemykin, Victor N; Hadt, Ryan G; Belosludov, Rodion V; Mizuseki, Hiroshi; Kawazoe, Yoshiyuki

    2007-12-20

    A time-dependent density functional theory (TDDFT) approach coupled with 14 different exchange-correlation functionals was used for the prediction of vertical excitation energies in zinc phthalocyanine (PcZn). In general, the TDDFT approach provides a more accurate description of both visible and ultraviolet regions of the UV-vis and magnetic circular dichroism (MCD) spectra of PcZn in comparison to the more popular semiempirical ZINDO/S and PM3 methods. It was found that the calculated vertical excitation energies of PcZn correlate with the amount of Hartree-Fock exchange involved in the exchange-correlation functional. The correlation was explained on the basis of the calculated difference in energy between occupied and unoccupied molecular orbitals. The influence of PcZn geometry, optimized using different exchange-correlation functionals, on the calculated vertical excitation energies in PcZn was found to be relatively small. The influence of solvents on the calculated vertical excitation energies in PcZn was considered for the first time using a polarized continuum model TDDFT (PCM-TDDFT) method and was found to be relatively small in excellent agreement with the experimental data. For all tested TDDFT and PCM-TDDFT cases, an assignment of the Q-band as an almost pure a1u (HOMO)-->eg (LUMO) transition, initially suggested by Gouterman, was confirmed. Pure exchange-correlation functionals indicate the presence of six 1Eu states in the B-band region of the UV-vis spectrum of PcZn, while hybrid exchange-correlation functionals predict only five 1Eu states for the same energy envelope. The first two symmetry-forbidden n-->pi* transitions were predicted in the Q0-2 region and in the low-energy tail of the B-band, while the first two symmetry-allowed n-->pi* transitions were found within the B-band energy envelope when pure exchange-correlation functionals were used for TDDFT calculations. The presence of a symmetry-forbidden but vibronically allowed n

  19. Benchmarking Density Functional Theory Based Methods To Model NiOOH Material Properties: Hubbard and van der Waals Corrections vs Hybrid Functionals.

    Science.gov (United States)

    Zaffran, Jeremie; Caspary Toroker, Maytal

    2016-08-09

    NiOOH has recently been used to catalyze water oxidation by way of electrochemical water splitting. Few experimental data are available to rationalize the successful catalytic capability of NiOOH. Thus, theory has a distinctive role for studying its properties. However, the unique layered structure of NiOOH is associated with the presence of essential dispersion forces within the lattice. Hence, the choice of an appropriate exchange-correlation functional within Density Functional Theory (DFT) is not straightforward. In this work, we will show that standard DFT is sufficient to evaluate the geometry, but DFT+U and hybrid functionals are required to calculate the oxidation states. Notably, the benefit of DFT with van der Waals correction is marginal. Furthermore, only hybrid functionals succeed in opening a bandgap, and such methods are necessary to study NiOOH electronic structure. In this work, we expect to give guidelines to theoreticians dealing with this material and to present a rational approach in the choice of the DFT method of calculation.

  20. Density Functional Theory applied to magnetic materials: Mn{sub 3}O{sub 4} at different hybrid functionals

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, R.A.P. [Department of Chemistry, State University of Ponta Grossa, Av. General Carlos Cavalcanti, 4748, 84030-900 Ponta Grossa, PR (Brazil); Lazaro, S.R. de, E-mail: srlazaro@upeg.br [Department of Chemistry, State University of Ponta Grossa, Av. General Carlos Cavalcanti, 4748, 84030-900 Ponta Grossa, PR (Brazil); Pianaro, S.A. [Department of Materials Engineering, State University of Ponta Grossa, Av. General Carlos Cavalcanti, 4748, 84030-900 Ponta Grossa, PR (Brazil)

    2015-10-01

    Antiferromagnetic Mn{sub 3}O{sub 4} in spinel structure was investigated employing the Density Functional Theory at different hybrid functionals with default HF exchange percentage. Structural, electronic and magnetic properties were examined. Structural results were in agreement with experimental and Hartree–Fock results showing that the octahedral site was distorted by the Jahn–Teller effect, which changed the electron density distribution. Band-gap results for B3LYP and B3PW hybrid functionals were closer to the experimental when compared to PBE0. Mulliken Population Analysis revealed magnetic moments very close to ideal d{sup 4} and d{sup 5} electron configurations of Mn{sup 3+} and Mn{sup 2+}, respectively. Electron density maps are useful to determine that oxygen atoms mediate the electron transfer between octahedral and tetrahedral clusters. Magnetic properties were investigated from theoretical results for exchange coupling constants. Intratetrahedral and tetra-octahedral interactions were observed to be antiferromagnetic, whereas, octahedral sites presented antiferromagnetic interactions in the same layer and ferromagnetic in adjacent layers. Results showed that only default B3LYP was successful to describe magnetic properties of antiferromagnetic materials in agreement with experimental results. - Highlights: • We study structural, electronic and magnetic properties of antiferromagnetic Mn{sub 3}O{sub 4}. • B3LYP, B3PW and PBE0 hybrid functionals are compared. • B3LYP and B3PW hybrid functionals are better to band-gap calculations. • Only default B3LYP was successful to describe exchange interactions for Mn{sub 3}O{sub 4}.

  1. Non-empirical exchange-correlation parameterizations based on exact conditions from correlated orbital theory.

    Science.gov (United States)

    Haiduke, Roberto Luiz A; Bartlett, Rodney J

    2018-05-14

    Some of the exact conditions provided by the correlated orbital theory are employed to propose new non-empirical parameterizations for exchange-correlation functionals from Density Functional Theory (DFT). This reparameterization process is based on range-separated functionals with 100% exact exchange for long-range interelectronic interactions. The functionals developed here, CAM-QTP-02 and LC-QTP, show mitigated self-interaction error, correctly predict vertical ionization potentials as the negative of eigenvalues for occupied orbitals, and provide nice excitation energies, even for challenging charge-transfer excited states. Moreover, some improvements are observed for reaction barrier heights with respect to the other functionals belonging to the quantum theory project (QTP) family. Finally, the most important achievement of these new functionals is an excellent description of vertical electron affinities (EAs) of atoms and molecules as the negative of appropriate virtual orbital eigenvalues. In this case, the mean absolute deviations for EAs in molecules are smaller than 0.10 eV, showing that physical interpretation can indeed be ascribed to some unoccupied orbitals from DFT.

  2. Non-empirical exchange-correlation parameterizations based on exact conditions from correlated orbital theory

    Science.gov (United States)

    Haiduke, Roberto Luiz A.; Bartlett, Rodney J.

    2018-05-01

    Some of the exact conditions provided by the correlated orbital theory are employed to propose new non-empirical parameterizations for exchange-correlation functionals from Density Functional Theory (DFT). This reparameterization process is based on range-separated functionals with 100% exact exchange for long-range interelectronic interactions. The functionals developed here, CAM-QTP-02 and LC-QTP, show mitigated self-interaction error, correctly predict vertical ionization potentials as the negative of eigenvalues for occupied orbitals, and provide nice excitation energies, even for challenging charge-transfer excited states. Moreover, some improvements are observed for reaction barrier heights with respect to the other functionals belonging to the quantum theory project (QTP) family. Finally, the most important achievement of these new functionals is an excellent description of vertical electron affinities (EAs) of atoms and molecules as the negative of appropriate virtual orbital eigenvalues. In this case, the mean absolute deviations for EAs in molecules are smaller than 0.10 eV, showing that physical interpretation can indeed be ascribed to some unoccupied orbitals from DFT.

  3. Performance of Density Functional Theory Procedures for the Calculation of Proton-Exchange Barriers: Unusual Behavior of M06-Type Functionals.

    Science.gov (United States)

    Chan, Bun; Gilbert, Andrew T B; Gill, Peter M W; Radom, Leo

    2014-09-09

    We have examined the performance of a variety of density functional theory procedures for the calculation of complexation energies and proton-exchange barriers, with a focus on the Minnesota-class of functionals that are generally highly robust and generally show good accuracy. A curious observation is that M05-type and M06-type methods show an atypical decrease in calculated barriers with increasing proportion of Hartree-Fock exchange. To obtain a clearer picture of the performance of the underlying components of M05-type and M06-type functionals, we have investigated the combination of MPW-type and PBE-type exchange and B95-type and PBE-type correlation procedures. We find that, for the extensive E3 test set, the general performance of the various hybrid-DFT procedures improves in the following order: PBE1-B95 → PBE1-PBE → MPW1-PBE → PW6-B95. As M05-type and M06-type procedures are related to PBE1-B95, it would be of interest to formulate and examine the general performance of an alternative Minnesota DFT method related to PW6-B95.

  4. Self-consistent hybrid functionals for solids: a fully-automated implementation

    Science.gov (United States)

    Erba, A.

    2017-08-01

    A fully-automated algorithm for the determination of the system-specific optimal fraction of exact exchange in self-consistent hybrid functionals of the density-functional-theory is illustrated, as implemented into the public Crystal program. The exchange fraction of this new class of functionals is self-consistently updated proportionally to the inverse of the dielectric response of the system within an iterative procedure (Skone et al 2014 Phys. Rev. B 89, 195112). Each iteration of the present scheme, in turn, implies convergence of a self-consistent-field (SCF) and a coupled-perturbed-Hartree-Fock/Kohn-Sham (CPHF/KS) procedure. The present implementation, beside improving the user-friendliness of self-consistent hybrids, exploits the unperturbed and electric-field perturbed density matrices from previous iterations as guesses for subsequent SCF and CPHF/KS iterations, which is documented to reduce the overall computational cost of the whole process by a factor of 2.

  5. Hybrid capacitive deionization with anion-exchange membranes for lithium extraction

    OpenAIRE

    Siekierka Anna; Bryjak Marek

    2017-01-01

    Lithium is considered to be a critical material for various industrial fields. We present our studies on extraction lithium from diluted aqueous solution by novel hybrid system based on a membrane capacitive deionization and batteries desalination. Hybrid CDI is comprised by a lithium selective adsorbent, activated carbon electrode and anion-exchange membranes. Here, we demonstrated implication of various type of anion-exchange membranes and influence their properties on effective capacity an...

  6. Plane-Wave Implementation and Performance of à-la-Carte Coulomb-Attenuated Exchange-Correlation Functionals for Predicting Optical Excitation Energies in Some Notorious Cases.

    Science.gov (United States)

    Bircher, Martin P; Rothlisberger, Ursula

    2018-06-12

    Linear-response time-dependent density functional theory (LR-TD-DFT) has become a valuable tool in the calculation of excited states of molecules of various sizes. However, standard generalized-gradient approximation and hybrid exchange-correlation (xc) functionals often fail to correctly predict charge-transfer (CT) excitations with low orbital overlap, thus limiting the scope of the method. The Coulomb-attenuation method (CAM) in the form of the CAM-B3LYP functional has been shown to reliably remedy this problem in many CT systems, making accurate predictions possible. However, in spite of a rather consistent performance across different orbital overlap regimes, some pitfalls remain. Here, we present a fully flexible and adaptable implementation of the CAM for Γ-point calculations within the plane-wave pseudopotential molecular dynamics package CPMD and explore how customized xc functionals can improve the optical spectra of some notorious cases. We find that results obtained using plane waves agree well with those from all-electron calculations employing atom-centered bases, and that it is possible to construct a new Coulomb-attenuated xc functional based on simple considerations. We show that such a functional is able to outperform CAM-B3LYP in some cases, while retaining similar accuracy in systems where CAM-B3LYP performs well.

  7. Recent developments in LIBXC - A comprehensive library of functionals for density functional theory

    Science.gov (United States)

    Lehtola, Susi; Steigemann, Conrad; Oliveira, Micael J. T.; Marques, Miguel A. L.

    2018-01-01

    LIBXC is a library of exchange-correlation functionals for density-functional theory. We are concerned with semi-local functionals (or the semi-local part of hybrid functionals), namely local-density approximations, generalized-gradient approximations, and meta-generalized-gradient approximations. Currently we include around 400 functionals for the exchange, correlation, and the kinetic energy, spanning more than 50 years of research. Moreover, LIBXC is by now used by more than 20 codes, not only from the atomic, molecular, and solid-state physics, but also from the quantum chemistry communities.

  8. Communication: Evaluating non-empirical double hybrid functionals for spin-state energetics in transition-metal complexes

    Science.gov (United States)

    Wilbraham, Liam; Adamo, Carlo; Ciofini, Ilaria

    2018-01-01

    The computationally assisted, accelerated design of inorganic functional materials often relies on the ability of a given electronic structure method to return the correct electronic ground state of the material in question. Outlining difficulties with current density functionals and wave function-based approaches, we highlight why double hybrid density functionals represent promising candidates for this purpose. In turn, we show that PBE0-DH (and PBE-QIDH) offers a significant improvement over its hybrid parent functional PBE0 [as well as B3LYP* and coupled cluster singles and doubles with perturbative triples (CCSD(T))] when computing spin-state splitting energies, using high-level diffusion Monte Carlo calculations as a reference. We refer to the opposing influence of Hartree-Fock (HF) exchange and MP2, which permits higher levels of HF exchange and a concomitant reduction in electronic density error, as the reason for the improved performance of double-hybrid functionals relative to hybrid functionals. Additionally, using 16 transition metal (Fe and Co) complexes, we show that low-spin states are stabilised by increasing contributions from MP2 within the double hybrid formulation. Furthermore, this stabilisation effect is more prominent for high field strength ligands than low field strength ligands.

  9. Reconsideration of data and correlations for plate finned-tube heat exchangers

    Science.gov (United States)

    Otović, Milena; Mihailović, Miloš; Genić, Srbislav; Jaćimović, Branislav; Milovančević, Uroš; Marković, Saša

    2018-04-01

    This paper deals with heat exchangers having plain finned tubes in staggered (triangular) pattern. The objective of this paper is to provide the heat transfer and friction factor correlation which can be used in engineering practice. For this purpose, the experimental data of several (most cited) authors who deal with this type of heat exchangers are used. The new correlations are established to predict the air-side heat transfer coefficient and friction factor as a function of the Reynolds number and geometric variables of the heat exchanger - tube diameter, tube pitch, fin spacing, tube rows, etc. In those correlations the characteristic dimension in Reynolds number is calculated by using the new parameter - volumetric porosity. Also, there are given the errors of those correlations.

  10. Extended screened exchange functional derived from transcorrelated density functional theory.

    Science.gov (United States)

    Umezawa, Naoto

    2017-09-14

    We propose a new formulation of the correlation energy functional derived from the transcorrelated method in use in density functional theory (TC-DFT). An effective Hamiltonian, H TC , is introduced by a similarity transformation of a many-body Hamiltonian, H, with respect to a complex function F: H TC =1FHF. It is proved that an expectation value of H TC for a normalized single Slater determinant, D n , corresponds to the total energy: E[n] = ⟨Ψ n |H|Ψ n ⟩/⟨Ψ n |Ψ n ⟩ = ⟨D n |H TC |D n ⟩ under the two assumptions: (1) The electron density nr associated with a trial wave function Ψ n = D n F is v-representable and (2) Ψ n and D n give rise to the same electron density nr. This formulation, therefore, provides an alternative expression of the total energy that is useful for the development of novel correlation energy functionals. By substituting a specific function for F, we successfully derived a model correlation energy functional, which resembles the functional form of the screened exchange method. The proposed functional, named the extended screened exchange (ESX) functional, is described within two-body integrals and is parametrized for a numerically exact correlation energy of the homogeneous electron gas. The ESX functional does not contain any ingredients of (semi-)local functionals and thus is totally free from self-interactions. The computational cost for solving the self-consistent-field equation is comparable to that of the Hartree-Fock method. We apply the ESX functional to electronic structure calculations for a solid silicon, H - ion, and small atoms. The results demonstrate that the TC-DFT formulation is promising for the systematic improvement of the correlation energy functional.

  11. libvdwxc: a library for exchange-correlation functionals in the vdW-DF family

    Science.gov (United States)

    Hjorth Larsen, Ask; Kuisma, Mikael; Löfgren, Joakim; Pouillon, Yann; Erhart, Paul; Hyldgaard, Per

    2017-09-01

    We present libvdwxc, a general library for evaluating the energy and potential for the family of vdW-DF exchange-correlation functionals. libvdwxc is written in C and provides an efficient implementation of the vdW-DF method and can be interfaced with various general-purpose DFT codes. Currently, the Gpaw and Octopus codes implement interfaces to libvdwxc. The present implementation emphasizes scalability and parallel performance, and thereby enables ab initio calculations of nanometer-scale complexes. The numerical accuracy is benchmarked on the S22 test set whereas parallel performance is benchmarked on ligand-protected gold nanoparticles ({{Au}}144{({{SC}}11{{NH}}25)}60) up to 9696 atoms.

  12. Influence of the exchange and correlation functional on the structure of amorphous InSb and In3SbTe2 compounds

    Science.gov (United States)

    Gabardi, Silvia; Caravati, Sebastiano; Los, Jan H.; Kühne, Thomas D.; Bernasconi, Marco

    2016-05-01

    We have investigated the structural, vibrational, and electronic properties of the amorphous phase of InSb and In3SbTe2 compounds of interest for applications in phase change non-volatile memories. Models of the amorphous phase have been generated by quenching from the melt by molecular dynamics simulations based on density functional theory. In particular, we have studied the dependence of the structural properties on the choice of the exchange-correlation functional. It turns out that the use of the Becke-Lee-Yang-Parr functional provides models with a much larger fraction of In atoms in a tetrahedral bonding geometry with respect to previous results obtained with the most commonly used Perdew-Becke-Ernzerhof functional. This outcome is at odd with the properties of Ge2Sb2Te5 phase change compound for which the two exchange-correlation functionals yield very similar results on the structure of the amorphous phase.

  13. Influence of the exchange and correlation functional on the structure of amorphous InSb and In3SbTe2 compounds

    International Nuclear Information System (INIS)

    Gabardi, Silvia; Caravati, Sebastiano; Bernasconi, Marco; Los, Jan H.; Kühne, Thomas D.

    2016-01-01

    We have investigated the structural, vibrational, and electronic properties of the amorphous phase of InSb and In 3 SbTe 2 compounds of interest for applications in phase change non-volatile memories. Models of the amorphous phase have been generated by quenching from the melt by molecular dynamics simulations based on density functional theory. In particular, we have studied the dependence of the structural properties on the choice of the exchange-correlation functional. It turns out that the use of the Becke-Lee-Yang-Parr functional provides models with a much larger fraction of In atoms in a tetrahedral bonding geometry with respect to previous results obtained with the most commonly used Perdew-Becke-Ernzerhof functional. This outcome is at odd with the properties of Ge 2 Sb 2 Te 5 phase change compound for which the two exchange-correlation functionals yield very similar results on the structure of the amorphous phase.

  14. Hybrid capacitive deionization with anion-exchange membranes for lithium extraction

    Directory of Open Access Journals (Sweden)

    Siekierka Anna

    2017-01-01

    Full Text Available Lithium is considered to be a critical material for various industrial fields. We present our studies on extraction lithium from diluted aqueous solution by novel hybrid system based on a membrane capacitive deionization and batteries desalination. Hybrid CDI is comprised by a lithium selective adsorbent, activated carbon electrode and anion-exchange membranes. Here, we demonstrated implication of various type of anion-exchange membranes and influence their properties on effective capacity and energy requirements in charge/discharge steps. We described a configuration with anion-exchange membrane characterized by adsorption capacity of 35 mg/g of Li+ with 0.08Wh/g and removal efficiency of 60 % of lithium ions, using novel selective desalination technique.

  15. Hybrid capacitive deionization with anion-exchange membranes for lithium extraction

    Science.gov (United States)

    Siekierka, Anna; Bryjak, Marek

    2017-11-01

    Lithium is considered to be a critical material for various industrial fields. We present our studies on extraction lithium from diluted aqueous solution by novel hybrid system based on a membrane capacitive deionization and batteries desalination. Hybrid CDI is comprised by a lithium selective adsorbent, activated carbon electrode and anion-exchange membranes. Here, we demonstrated implication of various type of anion-exchange membranes and influence their properties on effective capacity and energy requirements in charge/discharge steps. We described a configuration with anion-exchange membrane characterized by adsorption capacity of 35 mg/g of Li+ with 0.08Wh/g and removal efficiency of 60 % of lithium ions, using novel selective desalination technique.

  16. Exact exchange-correlation potentials of singlet two-electron systems

    Science.gov (United States)

    Ryabinkin, Ilya G.; Ospadov, Egor; Staroverov, Viktor N.

    2017-10-01

    We suggest a non-iterative analytic method for constructing the exchange-correlation potential, v XC ( r ) , of any singlet ground-state two-electron system. The method is based on a convenient formula for v XC ( r ) in terms of quantities determined only by the system's electronic wave function, exact or approximate, and is essentially different from the Kohn-Sham inversion technique. When applied to Gaussian-basis-set wave functions, the method yields finite-basis-set approximations to the corresponding basis-set-limit v XC ( r ) , whereas the Kohn-Sham inversion produces physically inappropriate (oscillatory and divergent) potentials. The effectiveness of the procedure is demonstrated by computing accurate exchange-correlation potentials of several two-electron systems (helium isoelectronic series, H2, H3 + ) using common ab initio methods and Gaussian basis sets.

  17. Ground-state properties of trapped Bose-Fermi mixtures: Role of exchange correlation

    International Nuclear Information System (INIS)

    Albus, Alexander P.; Wilkens, Martin; Illuminati, Fabrizio

    2003-01-01

    We introduce density-functional theory for inhomogeneous Bose-Fermi mixtures, derive the associated Kohn-Sham equations, and determine the exchange-correlation energy in local-density approximation. We solve numerically the Kohn-Sham system, and determine the boson and fermion density distributions and the ground-state energy of a trapped, dilute mixture beyond mean-field approximation. The importance of the corrections due to exchange correlation is discussed by a comparison with current experiments; in particular, we investigate the effect of the repulsive potential-energy contribution due to exchange correlation on the stability of the mixture against collapse

  18. Affordable and accurate large-scale hybrid-functional calculations on GPU-accelerated supercomputers

    Science.gov (United States)

    Ratcliff, Laura E.; Degomme, A.; Flores-Livas, José A.; Goedecker, Stefan; Genovese, Luigi

    2018-03-01

    Performing high accuracy hybrid functional calculations for condensed matter systems containing a large number of atoms is at present computationally very demanding or even out of reach if high quality basis sets are used. We present a highly optimized multiple graphics processing unit implementation of the exact exchange operator which allows one to perform fast hybrid functional density-functional theory (DFT) calculations with systematic basis sets without additional approximations for up to a thousand atoms. With this method hybrid DFT calculations of high quality become accessible on state-of-the-art supercomputers within a time-to-solution that is of the same order of magnitude as traditional semilocal-GGA functionals. The method is implemented in a portable open-source library.

  19. The effect of basis set and exchange-correlation functional on time-dependent density functional theory calculations within the Tamm-Dancoff approximation of the x-ray emission spectroscopy of transition metal complexes.

    Science.gov (United States)

    Roper, Ian P E; Besley, Nicholas A

    2016-03-21

    The simulation of X-ray emission spectra of transition metal complexes with time-dependent density functional theory (TDDFT) is investigated. X-ray emission spectra can be computed within TDDFT in conjunction with the Tamm-Dancoff approximation by using a reference determinant with a vacancy in the relevant core orbital, and these calculations can be performed using the frozen orbital approximation or with the relaxation of the orbitals of the intermediate core-ionised state included. Both standard exchange-correlation functionals and functionals specifically designed for X-ray emission spectroscopy are studied, and it is shown that the computed spectral band profiles are sensitive to the exchange-correlation functional used. The computed intensities of the spectral bands can be rationalised by considering the metal p orbital character of the valence molecular orbitals. To compute X-ray emission spectra with the correct energy scale allowing a direct comparison with experiment requires the relaxation of the core-ionised state to be included and the use of specifically designed functionals with increased amounts of Hartree-Fock exchange in conjunction with high quality basis sets. A range-corrected functional with increased Hartree-Fock exchange in the short range provides transition energies close to experiment and spectral band profiles that have a similar accuracy to those from standard functionals.

  20. Exact exchange-correlation potential and approximate exchange potential in terms of density matrices

    International Nuclear Information System (INIS)

    Holas, A.; March, N.H.

    1995-01-01

    An exact expression in terms of density matrices (DM) is derived for δF[n]/δn(r), the functional derivative of the Hohenberg-Kohn functional. The derivation starts from the differential form of the virial theorem, obtained here for an electron system with arbitrary interactions, and leads to an expression taking the form of an integral over a path that can be chosen arbitrarily. After applying this approach to the equivalent system of noninteracting electrons (Slater-Kohn-Sham scheme) and combining the corresponding result with the previous one, an exact expression for the exchange-correlation potential v xc (r) is obtained which is analogous in character to that for δF[n]/δn(r), but involving, besides the interacting-system DMs, also the noninteracitng DMs. Equating the former DMs to the latter ones, we reduce the result for the exact v xc (r) to that for an approximate exchange-only potential v x (r). This leads naturally to the Harbola-Sahni exchange-only potential

  1. Balancing Exchange Mixing in Density-Functional Approximations for Iron Porphyrin.

    Science.gov (United States)

    Berryman, Victoria E J; Boyd, Russell J; Johnson, Erin R

    2015-07-14

    Predicting the correct ground-state multiplicity for iron(II) porphyrin, a high-spin quintet, remains a significant challenge for electronic-structure methods, including commonly employed density functionals. An even greater challenge for these methods is correctly predicting favorable binding of O2 to iron(II) porphyrin, due to the open-shell singlet character of the adduct. In this work, the performance of a modest set of contemporary density-functional approximations is assessed and the results interpreted using Bader delocalization indices. It is found that inclusion of greater proportions of Hartree-Fock exchange, in hybrid or range-separated hybrid functionals, has opposing effects; it improves the ability of the functional to identify the ground state but is detrimental to predicting favorable dioxygen binding. Because of the uncomplementary nature of these properties, accurate prediction of both the relative spin-state energies and the O2 binding enthalpy eludes conventional density-functional approximations.

  2. Quantum dust magnetosonic waves with spin and exchange correlation effects

    Energy Technology Data Exchange (ETDEWEB)

    Maroof, R.; Qamar, A. [Department of Physics, University of Peshawar, Peshawar 25000 (Pakistan); Mushtaq, A. [Department of Physics, Abdul Wali Khan University, Mardan 23200 (Pakistan); National Center for Physics, Shahdra Valley Road, Islamabad 44000 (Pakistan)

    2016-01-15

    Dust magnetosonic waves are studied in degenerate dusty plasmas with spin and exchange correlation effects. Using the fluid equations of magnetoplasma with quantum corrections due to the Bohm potential, temperature degeneracy, spin magnetization energy, and exchange correlation, a generalized dispersion relation is derived. Spin effects are incorporated via spin force and macroscopic spin magnetization current. The exchange-correlation potentials are used, based on the adiabatic local-density approximation, and can be described as a function of the electron density. For three different values of angle, the dispersion relation is reduced to three different modes under the low frequency magnetohydrodynamic assumptions. It is found that the effects of quantum corrections in the presence of dust concentration significantly modify the dispersive properties of these modes. The results are useful for understanding numerous collective phenomena in quantum plasmas, such as those in compact astrophysical objects (e.g., the cores of white dwarf stars and giant planets) and in plasma-assisted nanotechnology (e.g., quantum diodes, quantum free-electron lasers, etc.)

  3. Quantum dust magnetosonic waves with spin and exchange correlation effects

    Science.gov (United States)

    Maroof, R.; Mushtaq, A.; Qamar, A.

    2016-01-01

    Dust magnetosonic waves are studied in degenerate dusty plasmas with spin and exchange correlation effects. Using the fluid equations of magnetoplasma with quantum corrections due to the Bohm potential, temperature degeneracy, spin magnetization energy, and exchange correlation, a generalized dispersion relation is derived. Spin effects are incorporated via spin force and macroscopic spin magnetization current. The exchange-correlation potentials are used, based on the adiabatic local-density approximation, and can be described as a function of the electron density. For three different values of angle, the dispersion relation is reduced to three different modes under the low frequency magnetohydrodynamic assumptions. It is found that the effects of quantum corrections in the presence of dust concentration significantly modify the dispersive properties of these modes. The results are useful for understanding numerous collective phenomena in quantum plasmas, such as those in compact astrophysical objects (e.g., the cores of white dwarf stars and giant planets) and in plasma-assisted nanotechnology (e.g., quantum diodes, quantum free-electron lasers, etc.).

  4. Self-Interaction Error in Density Functional Theory: An Appraisal.

    Science.gov (United States)

    Bao, Junwei Lucas; Gagliardi, Laura; Truhlar, Donald G

    2018-05-03

    Self-interaction error (SIE) is considered to be one of the major sources of error in most approximate exchange-correlation functionals for Kohn-Sham density-functional theory (KS-DFT), and it is large with all local exchange-correlation functionals and with some hybrid functionals. In this work, we consider systems conventionally considered to be dominated by SIE. For these systems, we demonstrate that by using multiconfiguration pair-density functional theory (MC-PDFT), the error of a translated local density-functional approximation is significantly reduced (by a factor of 3) when using an MCSCF density and on-top density, as compared to using KS-DFT with the parent functional; the error in MC-PDFT with local on-top functionals is even lower than the error in some popular KS-DFT hybrid functionals. Density-functional theory, either in MC-PDFT form with local on-top functionals or in KS-DFT form with some functionals having 50% or more nonlocal exchange, has smaller errors for SIE-prone systems than does CASSCF, which has no SIE.

  5. Influence of the exchange and correlation functional on the structure of amorphous InSb and In{sub 3}SbTe{sub 2} compounds

    Energy Technology Data Exchange (ETDEWEB)

    Gabardi, Silvia; Caravati, Sebastiano; Bernasconi, Marco, E-mail: marco.bernasconi@mater.unimib.it [Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via R. Cozzi 55, I-20125 Milano (Italy); Los, Jan H.; Kühne, Thomas D. [Institute of Physical Chemistry and Center for Computational Sciences, Johannes Gutenberg University Mainz, Staudinger Weg 7, D-55128 Mainz (Germany)

    2016-05-28

    We have investigated the structural, vibrational, and electronic properties of the amorphous phase of InSb and In{sub 3}SbTe{sub 2} compounds of interest for applications in phase change non-volatile memories. Models of the amorphous phase have been generated by quenching from the melt by molecular dynamics simulations based on density functional theory. In particular, we have studied the dependence of the structural properties on the choice of the exchange-correlation functional. It turns out that the use of the Becke-Lee-Yang-Parr functional provides models with a much larger fraction of In atoms in a tetrahedral bonding geometry with respect to previous results obtained with the most commonly used Perdew-Becke-Ernzerhof functional. This outcome is at odd with the properties of Ge{sub 2}Sb{sub 2}Te{sub 5} phase change compound for which the two exchange-correlation functionals yield very similar results on the structure of the amorphous phase.

  6. Kohn–Sham exchange-correlation potentials from second-order reduced density matrices

    Energy Technology Data Exchange (ETDEWEB)

    Cuevas-Saavedra, Rogelio; Staroverov, Viktor N., E-mail: vstarove@uwo.ca [Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7 (Canada); Ayers, Paul W. [Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8S 4M1 (Canada)

    2015-12-28

    We describe a practical algorithm for constructing the Kohn–Sham exchange-correlation potential corresponding to a given second-order reduced density matrix. Unlike conventional Kohn–Sham inversion methods in which such potentials are extracted from ground-state electron densities, the proposed technique delivers unambiguous results in finite basis sets. The approach can also be used to separate approximately the exchange and correlation potentials for a many-electron system for which the reduced density matrix is known. The algorithm is implemented for configuration-interaction wave functions and its performance is illustrated with numerical examples.

  7. A self-interaction-free local hybrid functional: Accurate binding energies vis-à-vis accurate ionization potentials from Kohn-Sham eigenvalues

    International Nuclear Information System (INIS)

    Schmidt, Tobias; Kümmel, Stephan; Kraisler, Eli; Makmal, Adi; Kronik, Leeor

    2014-01-01

    We present and test a new approximation for the exchange-correlation (xc) energy of Kohn-Sham density functional theory. It combines exact exchange with a compatible non-local correlation functional. The functional is by construction free of one-electron self-interaction, respects constraints derived from uniform coordinate scaling, and has the correct asymptotic behavior of the xc energy density. It contains one parameter that is not determined ab initio. We investigate whether it is possible to construct a functional that yields accurate binding energies and affords other advantages, specifically Kohn-Sham eigenvalues that reliably reflect ionization potentials. Tests for a set of atoms and small molecules show that within our local-hybrid form accurate binding energies can be achieved by proper optimization of the free parameter in our functional, along with an improvement in dissociation energy curves and in Kohn-Sham eigenvalues. However, the correspondence of the latter to experimental ionization potentials is not yet satisfactory, and if we choose to optimize their prediction, a rather different value of the functional's parameter is obtained. We put this finding in a larger context by discussing similar observations for other functionals and possible directions for further functional development that our findings suggest

  8. Understanding volatility correlation behavior with a magnitude cross-correlation function

    Science.gov (United States)

    Jun, Woo Cheol; Oh, Gabjin; Kim, Seunghwan

    2006-06-01

    We propose an approach for analyzing the basic relation between correlation properties of the original signal and its magnitude fluctuations by decomposing the original signal into its positive and negative fluctuation components. We use this relation to understand the following phenomenon found in many naturally occurring time series: the magnitude of the signal exhibits long-range correlation, whereas the original signal is short-range correlated. The applications of our approach to heart rate variability signals and high-frequency foreign exchange rates reveal that the difference between the correlation properties of the original signal and its magnitude fluctuations is induced by the time organization structure of the correlation function between the magnitude fluctuations of positive and negative components. We show that this correlation function can be described well by a stretched-exponential function and is related to the nonlinearity and the multifractal structure of the signals.

  9. Understanding volatility correlation behavior with a magnitude cross-correlation function.

    Science.gov (United States)

    Jun, Woo Cheol; Oh, Gabjin; Kim, Seunghwan

    2006-06-01

    We propose an approach for analyzing the basic relation between correlation properties of the original signal and its magnitude fluctuations by decomposing the original signal into its positive and negative fluctuation components. We use this relation to understand the following phenomenon found in many naturally occurring time series: the magnitude of the signal exhibits long-range correlation, whereas the original signal is short-range correlated. The applications of our approach to heart rate variability signals and high-frequency foreign exchange rates reveal that the difference between the correlation properties of the original signal and its magnitude fluctuations is induced by the time organization structure of the correlation function between the magnitude fluctuations of positive and negative components. We show that this correlation function can be described well by a stretched-exponential function and is related to the nonlinearity and the multifractal structure of the signals.

  10. Current Density Functional Theory Using Meta-Generalized Gradient Exchange-Correlation Functionals.

    Science.gov (United States)

    Furness, James W; Verbeke, Joachim; Tellgren, Erik I; Stopkowicz, Stella; Ekström, Ulf; Helgaker, Trygve; Teale, Andrew M

    2015-09-08

    We present the self-consistent implementation of current-dependent (hybrid) meta-generalized gradient approximation (mGGA) density functionals using London atomic orbitals. A previously proposed generalized kinetic energy density is utilized to implement mGGAs in the framework of Kohn-Sham current density functional theory (KS-CDFT). A unique feature of the nonperturbative implementation of these functionals is the ability to seamlessly explore a wide range of magnetic fields up to 1 au (∼235 kT) in strength. CDFT functionals based on the TPSS and B98 forms are investigated, and their performance is assessed by comparison with accurate coupled-cluster singles, doubles, and perturbative triples (CCSD(T)) data. In the weak field regime, magnetic properties such as magnetizabilities and nuclear magnetic resonance shielding constants show modest but systematic improvements over generalized gradient approximations (GGA). However, in the strong field regime, the mGGA-based forms lead to a significantly improved description of the recently proposed perpendicular paramagnetic bonding mechanism, comparing well with CCSD(T) data. In contrast to functionals based on the vorticity, these forms are found to be numerically stable, and their accuracy at high field suggests that the extension of mGGAs to CDFT via the generalized kinetic energy density should provide a useful starting point for further development of CDFT approximations.

  11. Objective-function Hybridization in Adjoint Seismic Tomography

    Science.gov (United States)

    Yuan, Y. O.; Bozdag, E.; Simons, F.; Gao, F.

    2016-12-01

    In the realm of seismic tomography, we are at the threshold of a new era of huge seismic datasets. However, how to assimilate as much information as possible from every seismogram is still a challenge. Cross-correlation measurements are generally tailored to some window selection algorithms, such as FLEXWIN (Maggie et al. 2008), to balance amplitude differences between seismic phases. However, these measurements naturally favor maximum picks in selected windows. It is also difficult to select all usable portions of seismograms in an optimum way that lots of information is generally lost, particularly the scattered waves. Instantaneous phase type of misfits extract information from every wiggle without cutting seismograms into small pieces, however, dealing with cycle skips at short periods can be challenging. For this purpose, we introduce a flexible hybrid approach for adjoint seismic tomography, to combine various objective functions. We initially focus on phase measurements and propose using instantaneous phase to take into account relatively small-magnitude scattered waves at long periods while using cross-correlation measurements on FLEXWIN windows to select distinct body-wave arrivals without complicating measurements due to non-linearities at short periods. To better deal with cycle skips and reliably measure instantaneous phases we design a new misfit function that incorporates instantaneous phase information implicitly instead of measuring it explicitly, through using normalized analytic signals. We present in our synthetic experiments how instantaneous phase, cross-correlation and their hybridization affect tomographic results. The combination of two different phase measurements in a hybrid approach constitutes progress towards using "anything and everything" in a data set, addressing data quality and measurement challenges simultaneously. We further extend hybridisation of misfit functions for amplitude measurements such as cross-correlation amplitude

  12. Short-range second order screened exchange correction to RPA correlation energies

    Science.gov (United States)

    Beuerle, Matthias; Ochsenfeld, Christian

    2017-11-01

    Direct random phase approximation (RPA) correlation energies have become increasingly popular as a post-Kohn-Sham correction, due to significant improvements over DFT calculations for properties such as long-range dispersion effects, which are problematic in conventional density functional theory. On the other hand, RPA still has various weaknesses, such as unsatisfactory results for non-isogyric processes. This can in parts be attributed to the self-correlation present in RPA correlation energies, leading to significant self-interaction errors. Therefore a variety of schemes have been devised to include exchange in the calculation of RPA correlation energies in order to correct this shortcoming. One of the most popular RPA plus exchange schemes is the second order screened exchange (SOSEX) correction. RPA + SOSEX delivers more accurate absolute correlation energies and also improves upon RPA for non-isogyric processes. On the other hand, RPA + SOSEX barrier heights are worse than those obtained from plain RPA calculations. To combine the benefits of RPA correlation energies and the SOSEX correction, we introduce a short-range RPA + SOSEX correction. Proof of concept calculations and benchmarks showing the advantages of our method are presented.

  13. General optimization procedure towards the design of a new family of minimal parameter spin-component-scaled double-hybrid density functional theory.

    Science.gov (United States)

    Roch, Loïc M; Baldridge, Kim K

    2017-10-04

    A general optimization procedure towards the development and implementation of a new family of minimal parameter spin-component-scaled double-hybrid (mSD) density functional theory (DFT) is presented. The nature of the proposed exchange-correlation functional establishes a methodology with minimal empiricism. This new family of double-hybrid (DH) density functionals is demonstrated using the PBEPBE functional, illustrating the optimization procedure to the mSD-PBEPBE method, and the performance characteristics shown for a set of non-covalent complexes covering a broad regime of weak interactions. With only two parameters, mSD-PBEPBE and its cost-effective counterpart, RI-mSD-PBEPBE, show a mean absolute error of ca. 0.4 kcal mol -1 averaged over 66 weak interacting systems. Following a successive 2D-grid refinement for a CBS extrapolation of the coefficients, the optimization procedure can be recommended for the design and implementation of a variety of additional DH methods using any of the plethora of currently available functionals.

  14. Alternative separation of exchange and correlation energies in multi-configuration range-separated density-functional theory.

    Science.gov (United States)

    Stoyanova, Alexandrina; Teale, Andrew M; Toulouse, Julien; Helgaker, Trygve; Fromager, Emmanuel

    2013-10-07

    The alternative separation of exchange and correlation energies proposed by Toulouse et al. [Theor. Chem. Acc. 114, 305 (2005)] is explored in the context of multi-configuration range-separated density-functional theory. The new decomposition of the short-range exchange-correlation energy relies on the auxiliary long-range interacting wavefunction rather than the Kohn-Sham (KS) determinant. The advantage, relative to the traditional KS decomposition, is that the wavefunction part of the energy is now computed with the regular (fully interacting) Hamiltonian. One potential drawback is that, because of double counting, the wavefunction used to compute the energy cannot be obtained by minimizing the energy expression with respect to the wavefunction parameters. The problem is overcome by using short-range optimized effective potentials (OEPs). The resulting combination of OEP techniques with wavefunction theory has been investigated in this work, at the Hartree-Fock (HF) and multi-configuration self-consistent-field (MCSCF) levels. In the HF case, an analytical expression for the energy gradient has been derived and implemented. Calculations have been performed within the short-range local density approximation on H2, N2, Li2, and H2O. Significant improvements in binding energies are obtained with the new decomposition of the short-range energy. The importance of optimizing the short-range OEP at the MCSCF level when static correlation becomes significant has also been demonstrated for H2, using a finite-difference gradient. The implementation of the analytical gradient for MCSCF wavefunctions is currently in progress.

  15. Assessing exchange-correlation functionals for elasticity and thermodynamics of α -ZrW2O8 : A density functional perturbation theory study

    Science.gov (United States)

    Weck, Philippe F.; Kim, Eunja; Greathouse, Jeffery A.; Gordon, Margaret E.; Bryan, Charles R.

    2018-04-01

    Elastic and thermodynamic properties of negative thermal expansion (NTE) α -ZrW2O8 have been calculated using PBEsol and PBE exchange-correlation functionals within the framework of density functional perturbation theory (DFPT). Measured elastic constants are reproduced within ∼ 2 % with PBEsol and ∼ 6 % with PBE. The thermal evolution of the Grüneisen parameter computed within the quasi-harmonic approximation exhibits negative values below the Debye temperature, consistent with observation. The standard molar heat capacity is predicted to be CP0 = 192.2 and 193.8 J mol-1K-1 with PBEsol and PBE, respectively. These results suggest superior accuracy of DFPT/PBEsol for studying the lattice dynamics, elasticity and thermodynamics of NTE materials.

  16. Kohn-Sham density functional theory for quantum wires in arbitrary correlation regimes

    NARCIS (Netherlands)

    Malet, F.; Mirtschink, A.P.; Cremon, J. C.; Reimann, S. M.; Gori Giorgi, P.

    2013-01-01

    We use the exact strong-interaction limit of the Hohenberg-Kohn energy density functional to construct an approximation for the exchange-correlation term of the Kohn-Sham approach. The resulting exchange-correlation potential is able to capture the features of the strongly correlated regime without

  17. Influence of Exchange-Correlation Functional in the Calculations of Vertical Excitation Energies of Halogenated Copper Phthalocyanines using Time-Dependent Density Functional Theory (TD-DFT)

    International Nuclear Information System (INIS)

    Lee, Sang Uck

    2013-01-01

    The accurate prediction of vertical excitation energies is very important for the development of new materials in the dye and pigment industry. A time-dependent density functional theory (TD-DFT) approach coupled with 22 different exchange-correlation functionals was used for the prediction of vertical excitation energies in the halogenated copper phthalocyanine molecules in order to find the most appropriate functional and to determine the accuracy of the prediction of the absorption wavelength and observed spectral shifts. Among the tested functional, B3LYP functional provides much more accurate vertical excitation energies and UV-vis spectra. Our results clearly provide a benchmark calibration of the TD-DFT method for phthalocyanine based dyes and pigments used in industry

  18. Strong Correlation in Kohn-Sham Density Functional Theory

    NARCIS (Netherlands)

    Malet, F.; Gori Giorgi, P.

    2012-01-01

    We use the exact strong-interaction limit of the Hohenberg-Kohn energy density functional to approximate the exchange-correlation energy of the restricted Kohn-Sham scheme. Our approximation corresponds to a highly nonlocal density functional whose functional derivative can be easily constructed,

  19. Long-range corrected density functional theory with accelerated Hartree-Fock exchange integration using a two-Gaussian operator [LC-ωPBE(2Gau)].

    Science.gov (United States)

    Song, Jong-Won; Hirao, Kimihiko

    2015-10-14

    Since the advent of hybrid functional in 1993, it has become a main quantum chemical tool for the calculation of energies and properties of molecular systems. Following the introduction of long-range corrected hybrid scheme for density functional theory a decade later, the applicability of the hybrid functional has been further amplified due to the resulting increased performance on orbital energy, excitation energy, non-linear optical property, barrier height, and so on. Nevertheless, the high cost associated with the evaluation of Hartree-Fock (HF) exchange integrals remains a bottleneck for the broader and more active applications of hybrid functionals to large molecular and periodic systems. Here, we propose a very simple yet efficient method for the computation of long-range corrected hybrid scheme. It uses a modified two-Gaussian attenuating operator instead of the error function for the long-range HF exchange integral. As a result, the two-Gaussian HF operator, which mimics the shape of the error function operator, reduces computational time dramatically (e.g., about 14 times acceleration in C diamond calculation using periodic boundary condition) and enables lower scaling with system size, while maintaining the improved features of the long-range corrected density functional theory.

  20. Exchange-coupled nanoscale SmCo/NdFeB hybrid magnets

    Energy Technology Data Exchange (ETDEWEB)

    Wang Dapeng; Poudyal, Narayan; Rong, Chuanbing [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States); Zhang Ying [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States); Materials Science and Engineering, Ames Laboratory, USDOE, Iowa State University, Ames, IA 50011 (United States); Kramer, M.J. [Materials Science and Engineering, Ames Laboratory, USDOE, Iowa State University, Ames, IA 50011 (United States); Liu, J. Ping, E-mail: pliu@uta.edu [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States)

    2012-09-15

    Nanoscale hybrid magnets containing SmCo{sub 5} and Nd{sub 2}Fe{sub 14}B hard magnetic phases have been produced via a novel 'in-one-pot' processing route. The grain size of the processed bulk composite materials is controlled below 20 nm. The refinement of the nanoscale morphology leads to effective inter-phase exchange coupling that results in single-phase like magnetic properties. Energy product of 14 MGOe was obtained in the isotropic nanocomposite magnets at room temperature. At elevated temperatures, the hybrid magnets have greatly improved thermal stability compared to the Nd{sub 2}Fe{sub 14}B single-phase counterpart and have substantially increased magnetization and energy products compared to the single-phase SmCo{sub 5} counterpart. - Highlights: Black-Right-Pointing-Pointer We realize interphase exchange coupling in nanoscale SmCo{sub 5}/Nd{sub 2}Fe{sub 14}B magnets. Black-Right-Pointing-Pointer We observe homogenously distributed two-phase grains with size smaller than 20 nm. Black-Right-Pointing-Pointer We observe a common Curie temperature in the hybrid magnet. Black-Right-Pointing-Pointer High-temperature magnetic properties of the hybrid magnets greatly improved. Black-Right-Pointing-Pointer Plastic deformation of composite materials leads to self-nanoscaling of grains.

  1. Theoretical modeling of the electronic structure and exchange interactions in Cu(II)Pc

    Science.gov (United States)

    Wu, Wei; Fisher, A. J.; Harrison, N. M.; Wang, Hai; Wu, Zhenlin; Gardener, Jules; Heutz, Sandrine; Jones, Tim; Aeppli, Gabriel

    2012-12-01

    We calculate the electronic structure and exchange interactions in a copper(II)phthalocyanine (Cu(II)Pc) crystal as a one-dimensional molecular chain using hybrid exchange density functional theory (DFT). In addition, the intermolecular exchange interactions are also calculated in a molecular dimer using Green's function perturbation theory (GFPT) to illustrate the underlying physics. We find that the exchange interactions depend strongly on the stacking angle, but weakly on the sliding angle (defined in the text). The hybrid DFT calculations also provide an insight into the electronic structure of the Cu(II)Pc molecular chain and demonstrate that on-site electron correlations have a significant effect on the nature of the ground state, the band gap and magnetic excitations. The exchange interactions predicted by our DFT calculations and GFPT calculations agree qualitatively with the recent experimental results on newly found η-Cu(II)Pc and the previous results for the α- and β-phases. This work provides a reliable theoretical basis for the further application of Cu(II)Pc to molecular spintronics and organic-based quantum information processing.

  2. Dispersion- and Exchange-Corrected Density Functional Theory for Sodium Ion Hydration.

    Science.gov (United States)

    Soniat, Marielle; Rogers, David M; Rempe, Susan B

    2015-07-14

    A challenge in density functional theory is developing functionals that simultaneously describe intermolecular electron correlation and electron delocalization. Recent exchange-correlation functionals address those two issues by adding corrections important at long ranges: an atom-centered pairwise dispersion term to account for correlation and a modified long-range component of the electron exchange term to correct for delocalization. Here we investigate how those corrections influence the accuracy of binding free energy predictions for sodium-water clusters. We find that the dual-corrected ωB97X-D functional gives cluster binding energies closest to high-level ab initio methods (CCSD(T)). Binding energy decomposition shows that the ωB97X-D functional predicts the smallest ion-water (pairwise) interaction energy and larger multibody contributions for a four-water cluster than most other functionals - a trend consistent with CCSD(T) results. Also, ωB97X-D produces the smallest amounts of charge transfer and the least polarizable waters of the density functionals studied, which mimics the lower polarizability of CCSD. When compared with experimental binding free energies, however, the exchange-corrected CAM-B3LYP functional performs best (error <1 kcal/mol), possibly because of its parametrization to experimental formation enthalpies. For clusters containing more than four waters, "split-shell" coordination must be considered to obtain accurate free energies in comparison with experiment.

  3. Quadratic integrand double-hybrid made spin-component-scaled

    Energy Technology Data Exchange (ETDEWEB)

    Brémond, Éric, E-mail: eric.bremond@iit.it; Savarese, Marika [CompuNet, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genoa (Italy); Sancho-García, Juan C.; Pérez-Jiménez, Ángel J. [Departamento de Química Física, Universidad de Alicante, E-03080 Alicante (Spain); Adamo, Carlo [CompuNet, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genoa (Italy); Chimie ParisTech, PSL Research University, CNRS, Institut de Recherche de Chimie Paris IRCP, F-75005 Paris (France); Institut Universitaire de France, 103 Boulevard Saint Michel, F-75005 Paris (France)

    2016-03-28

    We propose two analytical expressions aiming to rationalize the spin-component-scaled (SCS) and spin-opposite-scaled (SOS) schemes for double-hybrid exchange-correlation density-functionals. Their performances are extensively tested within the framework of the nonempirical quadratic integrand double-hybrid (QIDH) model on energetic properties included into the very large GMTKN30 benchmark database, and on structural properties of semirigid medium-sized organic compounds. The SOS variant is revealed as a less computationally demanding alternative to reach the accuracy of the original QIDH model without losing any theoretical background.

  4. Gamow-Teller strength function for 90Zr: Effects of spin and isospin exchange forces, and ground-state correlations

    International Nuclear Information System (INIS)

    Mathews, G.J.; Bloom, S.D.; Hausman, R.F. Jr.

    1983-01-01

    Shell-model calculations of the Gamow-Teller strength function for 90 Zr have been performed utilizing a realistic finite-range two-body interaction in a model space consisting of the 2p and 1g shells. The effects of admixtures of two-particle two-hole excitations in 90 Nb, mostly due to the spin and isospin exchange components of the nucleon-nucleon force, are discussed. Ground state correlations in 90 Zr are also added via seniority-zero two-proton excitations from the 2p shell into the 1g/sub 9/2/ shell. With the correlations the Gamow-Teller strength function is in good agreement with the experimental results and accounts for essentially all of the observed dispersion of strength. The inclusion of these correlations does not, however, produce either a displacement of Gamow-Teller strength to higher excitation energies, or a significant change in the total strength. Thus, they cannot account for the observed Gamow-Teller quenching. The quenching factor derived by a comparison of our calculated results with experiment is 0.52

  5. 3d-4f magnetic interaction with density functional theory plus u approach: local Coulomb correlation and exchange pathways.

    Science.gov (United States)

    Zhang, Yachao; Yang, Yang; Jiang, Hong

    2013-12-12

    The 3d-4f exchange interaction plays an important role in many lanthanide based molecular magnetic materials such as single-molecule magnets and magnetic refrigerants. In this work, we study the 3d-4f magnetic exchange interactions in a series of Cu(II)-Gd(III) (3d(9)-4f(7)) dinuclear complexes based on the numerical atomic basis-norm-conserving pseudopotential method and density functional theory plus the Hubbard U correction approach (DFT+U). We obtain improved description of the 4f electrons by including the semicore 5s5p states in the valence part of the Gd-pseudopotential. The Hubbard U correction is employed to treat the strongly correlated Cu-3d and Gd-4f electrons, which significantly improve the agreement of the predicted exchange constants, J, with experiment, indicating the importance of accurate description of the local Coulomb correlation. The high efficiency of the DFT+U approach enables us to perform calculations with molecular crystals, which in general improve the agreement between theory and experiment, achieving a mean absolute error smaller than 2 cm(-1). In addition, through analyzing the physical effects of U, we identify two magnetic exchange pathways. One is ferromagnetic and involves an interaction between the Cu-3d, O-2p (bridge ligand), and the majority-spin Gd-5d orbitals. The other one is antiferromagnetic and involves Cu-3d, O-2p, and the empty minority-spin Gd-4f orbitals, which is suppressed by the planar Cu-O-O-Gd structure. This study demonstrates the accuracy of the DFT+U method for evaluating the 3d-4f exchange interactions, provides a better understanding of the exchange mechanism in the Cu(II)-Gd(III) complexes, and paves the way for exploiting the magnetic properties of the 3d-4f compounds containing lanthanides other than Gd.

  6. Density functional study of photoabsorption in metallic clusters using an exchange-correlation potential with correct long-range behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Torres, M.B. [Dpto. de Matematicas y Computacion, Universidad de Burgos, Burgos (Spain); Balbas, L.C. [Dpto. de Fisica Teorica, Universidad de Valladolid, Valladolid (Spain)

    2002-06-17

    The atomic exchange-correlation (xc) potential with the correct -1/r asymptotic behaviour constructed by Parr and Ghosh (Parr R G and Ghosh S K 1995 Phys. Rev. A 51 3564) is adapted here to study, within time density functional theory, the linear response to external fields of (i) neutral and charged sodium clusters, and (ii) doped clusters of the type Na{sub n}Pb (n=4, 6, 16). The resulting photoabsorption cross sections are compared to experimental results, when available, and to results from previous calculations using local and non-local xc functionals. The calculated static polarizabilities and plasmon frequencies are closer to the experimental values than previous results. (author)

  7. Exact exchange and Wilson-Levy correlation: a pragmatic device for studying complex weakly-bonded systems.

    Science.gov (United States)

    Walsh, T R

    2005-02-07

    The Wilson-Levy (WL) correlation functional is used together with Hartree-Fock (HF) theory to evaluate interaction energies at intermediate separations (i.e. around equilibrium separation) for several weakly-bonded systems. The HF+WL approach reproduces binding trends for all complexes studied: selected rare-gas dimers, isomers of the methane dimer, benzene dimer and naphthalene dimer, and base-pair stacking structures for pyrimidine, cytosine, uracil and guanine dimers. These HF+WL data are contrasted against results obtained from some popular functionals (including B3LYP and PBE), as well as two newly-developed functionals, X3LYP and xPBE. The utility of HF+WL, with reference to exact-exchange (EXX) density-functional theory, is discussed in terms of a suggested EXXWL exchange-correlation functional.

  8. Calculation of strained BaTiO3 with different exchange correlation functionals examined with criterion by Ginzburg-Landau theory, uncovering expressions by crystallographic parameters

    Science.gov (United States)

    Watanabe, Yukio

    2018-05-01

    In the calculations of tetragonal BaTiO3, some exchange-correlation (XC) energy functionals such as local density approximation (LDA) have shown good agreement with experiments at room temperature (RT), e.g., spontaneous polarization (PS), and superiority compared with other XC functionals. This is due to the error compensation of the RT effect and, hence, will be ineffective in the heavily strained case such as domain boundaries. Here, ferroelectrics under large strain at RT are approximated as those at 0 K because the strain effect surpasses the RT effects. To find effective XC energy functionals for strained BaTiO3, we propose a new comparison, i.e., a criterion. This criterion is the properties at 0 K given by the Ginzburg-Landau (GL) theory because GL theory is a thermodynamic description of experiments working under the same symmetry-constraints as ab initio calculations. With this criterion, we examine LDA, generalized gradient approximations (GGA), meta-GGA, meta-GGA + local correlation potential (U), and hybrid functionals, which reveals the high accuracy of some XC functionals superior to XC functionals that have been regarded as accurate. This result is examined directly by the calculations of homogenously strained tetragonal BaTiO3, confirming the validity of the new criterion. In addition, the data points of theoretical PS vs. certain crystallographic parameters calculated with different XC functionals are found to lie on a single curve, despite their wide variations. Regarding these theoretical data points as corresponding to the experimental results, analytical expressions of the local PS using crystallographic parameters are uncovered. These expressions show the primary origin of BaTiO3 ferroelectricity as oxygen displacements. Elastic compliance and electrostrictive coefficients are estimated. For the comparison of strained results, we show that the effective critical temperature TC under strain 1000 K from an approximate method combining ab initio

  9. Cross-correlations between RMB exchange rate and international commodity markets

    Science.gov (United States)

    Lu, Xinsheng; Li, Jianfeng; Zhou, Ying; Qian, Yubo

    2017-11-01

    This paper employs multifractal detrended analysis (MF-DFA) and multifractal detrended cross-correlation analysis (MF-DCCA) to study cross-correlation behaviors between China's RMB exchange rate market and four international commodity markets, using a comprehensive set of data covering the period from 22 July 2005 to 15 March 2016. Our empirical results from MF-DFA indicate that the RMB exchange rate is the most inefficient among the 4 selected markets. The results from quantitative analysis have testified the existence of cross-correlations and the result from MF-DCCA have further confirmed a strong multifractal behavior between RMB exchange rate and international commodity markets. We also demonstrate that the recent financial crisis has significant impact on the cross-correlated behavior. Through the rolling window analysis, we find that the RMB exchange rates and international commodity prices are anti-persistent cross-correlated. The main sources of multifractality in the cross-correlations are long-range correlations between RMB exchange rate and the aggregate commodity, energy and metals index.

  10. A hybrid correlation analysis with application to imaging genetics

    Science.gov (United States)

    Hu, Wenxing; Fang, Jian; Calhoun, Vince D.; Wang, Yu-Ping

    2018-03-01

    Investigating the association between brain regions and genes continues to be a challenging topic in imaging genetics. Current brain region of interest (ROI)-gene association studies normally reduce data dimension by averaging the value of voxels in each ROI. This averaging may lead to a loss of information due to the existence of functional sub-regions. Pearson correlation is widely used for association analysis. However, it only detects linear correlation whereas nonlinear correlation may exist among ROIs. In this work, we introduced distance correlation to ROI-gene association analysis, which can detect both linear and nonlinear correlations and overcome the limitation of averaging operations by taking advantage of the information at each voxel. Nevertheless, distance correlation usually has a much lower value than Pearson correlation. To address this problem, we proposed a hybrid correlation analysis approach, by applying canonical correlation analysis (CCA) to the distance covariance matrix instead of directly computing distance correlation. Incorporating CCA into distance correlation approach may be more suitable for complex disease study because it can detect highly associated pairs of ROI and gene groups, and may improve the distance correlation level and statistical power. In addition, we developed a novel nonlinear CCA, called distance kernel CCA, which seeks the optimal combination of features with the most significant dependence. This approach was applied to imaging genetic data from the Philadelphia Neurodevelopmental Cohort (PNC). Experiments showed that our hybrid approach produced more consistent results than conventional CCA across resampling and both the correlation and statistical significance were increased compared to distance correlation analysis. Further gene enrichment analysis and region of interest (ROI) analysis confirmed the associations of the identified genes with brain ROIs. Therefore, our approach provides a powerful tool for finding

  11. Efficient exact-exchange time-dependent density-functional theory methods and their relation to time-dependent Hartree-Fock.

    Science.gov (United States)

    Hesselmann, Andreas; Görling, Andreas

    2011-01-21

    A recently introduced time-dependent exact-exchange (TDEXX) method, i.e., a response method based on time-dependent density-functional theory that treats the frequency-dependent exchange kernel exactly, is reformulated. In the reformulated version of the TDEXX method electronic excitation energies can be calculated by solving a linear generalized eigenvalue problem while in the original version of the TDEXX method a laborious frequency iteration is required in the calculation of each excitation energy. The lowest eigenvalues of the new TDEXX eigenvalue equation corresponding to the lowest excitation energies can be efficiently obtained by, e.g., a version of the Davidson algorithm appropriate for generalized eigenvalue problems. Alternatively, with the help of a series expansion of the new TDEXX eigenvalue equation, standard eigensolvers for large regular eigenvalue problems, e.g., the standard Davidson algorithm, can be used to efficiently calculate the lowest excitation energies. With the help of the series expansion as well, the relation between the TDEXX method and time-dependent Hartree-Fock is analyzed. Several ways to take into account correlation in addition to the exact treatment of exchange in the TDEXX method are discussed, e.g., a scaling of the Kohn-Sham eigenvalues, the inclusion of (semi)local approximate correlation potentials, or hybrids of the exact-exchange kernel with kernels within the adiabatic local density approximation. The lowest lying excitations of the molecules ethylene, acetaldehyde, and pyridine are considered as examples.

  12. Ion exchange removal of chromium (iii) from tannery wastes by using a strong acid cation exchange resin amberlite ir-120 h+ and its hybrids

    International Nuclear Information System (INIS)

    Ahmad, T.

    2014-01-01

    A strong acid cation exchange resin Amberlite IR-120 H+ and its hybrids with Mn(OH)/sub 2/, Cu(OH)/sub 2/ and Fe(OH)/sub 3/ are used for the removal of chromium (III) from spent tannery bath. The experimental data give good fits with the Langmuir sorption model. The thermodynamic parameters entropy (delta S), enthalpy (delta H) and free energy (delta G) changes are computed, which reveal that the chromium removal from tannery wastes by ion exchangers is an endothermic, physical sorption and entropically driven process. The rate of sorption is found to increase with the increase of resin dosage, stirring speed and temperature. Different kinetic models such as film diffusion, particle diffusion and Lagergren pseudo first order are used to evaluate the mechanism of the process. It is found that the hybrid ion exchange resins have better removal capacity as compared to the parent ion exchanger. The increase in the removal capacity is found to be in the order of the corresponding PZC values of the hybrid ion exchangers. Further, it is suggested that the higher exchange capacity is the result of Donnan effect and specific adsorption of chromium by the oxides / hydroxides present inside the matrix of the organic cation exchanger. (author)

  13. Dynamic polarization in paramagnetic solids and microscopic correlation functions

    International Nuclear Information System (INIS)

    Boucher, Jean-Paul

    1972-01-01

    The different effects of Dynamic Nuclear Polarization in paramagnetic solids are described by means of a single thermodynamic formalism. In the case of large exchange interactions, the Overhauser effect correlated with nuclear relaxation time measurements can provide a way of studying correlation functions between electronic spins. This method is used to study the low-frequency behaviour of the microscopic spectral density which should diverge as ω → 0, in the case of a linear exchange chain. (author) [fr

  14. Communication: Hole localization in Al-doped quartz SiO{sub 2} within ab initio hybrid-functional DFT

    Energy Technology Data Exchange (ETDEWEB)

    Gerosa, Matteo [Department of Energy, Politecnico di Milano, via Ponzio 34/3, 20133 Milano (Italy); Di Valentin, Cristiana; Pacchioni, Gianfranco [Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi 55, 20125 Milan (Italy); Bottani, Carlo Enrico, E-mail: carlo.bottani@polimi.it [Department of Energy, Politecnico di Milano, via Ponzio 34/3, 20133 Milano (Italy); Center for Nano Science and Technology @Polimi, Istituto Italiano di Tecnologia, via Pascoli 70/3, 20133 Milano (Italy); Onida, Giovanni [Dipartimento di Fisica dell’ Universita’ degli Studi di Milano and European Theoretical Spectroscopy Facility (ETSF), Via Celoria 16, 20133 Milan (Italy)

    2015-09-21

    We investigate the long-standing problem of hole localization at the Al impurity in quartz SiO{sub 2}, using a relatively recent DFT hybrid-functional method in which the exchange fraction is obtained ab initio, based on an analogy with the static many-body COHSEX approximation to the electron self-energy. As the amount of the admixed exact exchange in hybrid functionals has been shown to be determinant for properly capturing the hole localization, this problem constitutes a prototypical benchmark for the accuracy of the method, allowing one to assess to what extent self-interaction effects are avoided. We obtain good results in terms of description of the charge localization and structural distortion around the Al center, improving with respect to the more popular B3LYP hybrid-functional approach. We also discuss the accuracy of computed hyperfine parameters, by comparison with previous calculations based on other self-interaction-free methods, as well as experimental values. We discuss and rationalize the limitations of our approach in computing defect-related excitation energies in low-dielectric-constant insulators.

  15. Influence of the exchange and correlation functional on the structure of amorphous InSb and In3SbTe2 compounds

    OpenAIRE

    Gabardi, Silvia; Caravati, Sebastiano; Los, Jan H; Kühne, Thomas D; Bernasconi, Marco

    2016-01-01

    We have investigated the structural, vibrational, and electronic properties of the amorphous phase of InSb and In3SbTe2 compounds of interest for applications in phase change non-volatile memories. Models of the amorphous phase have been generated by quenching from the melt by molecular dynamics simulations based on density functional theory. In particular, we have studied the dependence of the structural properties on the choice of the exchange-correlation functional. It turns out that the u...

  16. Valence electronic structure of cobalt phthalocyanine from an optimally tuned range-separated hybrid functional.

    Science.gov (United States)

    Brumboiu, Iulia Emilia; Prokopiou, Georgia; Kronik, Leeor; Brena, Barbara

    2017-07-28

    We analyse the valence electronic structure of cobalt phthalocyanine (CoPc) by means of optimally tuning a range-separated hybrid functional. The tuning is performed by modifying both the amount of short-range exact exchange (α) included in the hybrid functional and the range-separation parameter (γ), with two strategies employed for finding the optimal γ for each α. The influence of these two parameters on the structural, electronic, and magnetic properties of CoPc is thoroughly investigated. The electronic structure is found to be very sensitive to the amount and range in which the exact exchange is included. The electronic structure obtained using the optimal parameters is compared to gas-phase photo-electron data and GW calculations, with the unoccupied states additionally compared with inverse photo-electron spectroscopy measurements. The calculated spectrum with tuned γ, determined for the optimal value of α = 0.1, yields a very good agreement with both experimental results and with GW calculations that well-reproduce the experimental data.

  17. Elliptically polarized electromagnetic waves in a magnetized quantum electron-positron plasma with effects of exchange-correlation

    Energy Technology Data Exchange (ETDEWEB)

    Shahmansouri, M., E-mail: mshmansouri@gmail.com [Department of Physics, Faculty of Science, Arak University, Arak 38156-8 8349 (Iran, Islamic Republic of); Misra, A. P., E-mail: apmisra@visva-bharati.ac.in, E-mail: apmisra@gmail.com [Department of Mathematics, Siksha Bhavana, Visva-Bharati University, Santiniketan 731 235, West Bengal (India)

    2016-07-15

    The dispersion properties of elliptically polarized electromagnetic waves in a magnetized electron-positron-pair (EP-pair) plasma are studied with the effects of particle dispersion associated with the Bohm potential, the Fermi degenerate pressure, and the exchange-correlation force. Two possible modes of the extraordinary or X wave, modified by these quantum effects, are identified and their propagation characteristics are investigated numerically. It is shown that the upper-hybrid frequency and the cutoff and resonance frequencies are no longer constants but are dispersive due to these quantum effects. It is found that the particle dispersion and the exchange-correlation force can have different dominating roles on each other depending on whether the X waves are of short or long wavelengths (in comparison with the Fermi Debye length). The present investigation should be useful for understanding the collective behaviors of EP plasma oscillations and the propagation of extraordinary waves in magnetized dense EP-pair plasmas.

  18. Exchange functional by a range-separated exchange hole

    International Nuclear Information System (INIS)

    Toyoda, Masayuki; Ozaki, Taisuke

    2011-01-01

    An approximation to the exchange-hole density is proposed for the evaluation of the exact exchange energy in electronic structure calculations within the density-functional theory and the Kohn-Sham scheme. Based on the localized nature of density matrix, the exchange hole is divided into the short-range (SR) and long-range (LR) parts by using an adequate filter function, where the LR part is deduced by matching of moments with the exactly calculated SR counterpart, ensuring the correct asymptotic -1/r behavior of the exchange potential. With this division, the time-consuming integration is truncated at a certain interaction range, largely reducing the computation cost. The total energies, exchange energies, exchange potentials, and eigenvalues of the highest-occupied orbitals are calculated for the noble-gas atoms. The close agreement of the results with the exact values suggests the validity of the approximation.

  19. van der Waals forces in density functional theory: Perturbational long-range electron-interaction corrections

    International Nuclear Information System (INIS)

    Angyan, Janos G.; Gerber, Iann C.; Savin, Andreas; Toulouse, Julien

    2005-01-01

    Long-range exchange and correlation effects, responsible for the failure of currently used approximate density functionals in describing van der Waals forces, are taken into account explicitly after a separation of the electron-electron interaction in the Hamiltonian into short- and long-range components. We propose a 'range-separated hybrid' functional based on a local density approximation for the short-range exchange-correlation energy, combined with a long-range exact exchange energy. Long-range correlation effects are added by a second-order perturbational treatment. The resulting scheme is general and is particularly well adapted to describe van der Waals complexes, such as rare gas dimers

  20. Continual Energy Management System of Proton Exchange Membrane Fuel Cell Hybrid Power Electric Vehicles

    Directory of Open Access Journals (Sweden)

    Ren Yuan

    2016-01-01

    Full Text Available Current research status in energy management of Proton Exchange Membrane (PEM fuel cell hybrid power electric vehicles are first described in this paper, and then build the PEMFC/ lithium-ion battery/ ultra-capacitor hybrid system model. The paper analysis the key factors of the continuous power available in PEM fuel cell hybrid power electric vehicle and hybrid power system working status under different driving modes. In the end this paper gives the working flow chart of the hybrid power system and concludes the three items of the system performance analysis.

  1. Hybrid-DFT  +  V w method for band structure calculation of semiconducting transition metal compounds: the case of cerium dioxide.

    Science.gov (United States)

    Ivády, Viktor; Gali, Adam; Abrikosov, Igor A

    2017-11-15

    Hybrid functionals' non-local exchange-correlation potential contains a derivative discontinuity that improves on standard semi-local density functional theory (DFT) band gaps. Moreover, by careful parameterization, hybrid functionals can provide self-interaction reduced description of selected states. On the other hand, the uniform description of all the electronic states of a given system is a known drawback of these functionals that causes varying accuracy in the description of states with different degrees of localization. This limitation can be remedied by the orbital dependent exact exchange extension of hybrid functionals; the hybrid-DFT  +  V w method (Ivády et al 2014 Phys. Rev. B 90 035146). Based on the analogy of quasi-particle equations and hybrid-DFT single particle equations, here we demonstrate that parameters of hybrid-DFT  +  V w functional can be determined from approximate theoretical quasi-particle spectra without any fitting to experiment. The proposed method is illustrated on the charge self-consistent electronic structure calculation for cerium dioxide where itinerant valence states interact with well-localized 4f atomic like states, making this system challenging for conventional methods, either hybrid-DFT or LDA  +  U, and therefore allowing for a demonstration of the advantages of the proposed scheme.

  2. Exact-exchange time-dependent density-functional theory for static and dynamic polarizabilities

    International Nuclear Information System (INIS)

    Hirata, So; Ivanov, Stanislav; Bartlett, Rodney J.; Grabowski, Ireneusz

    2005-01-01

    Time-dependent density-functional theory (TDDFT) employing the exact-exchange functional has been formulated on the basis of the optimized-effective-potential (OEP) method of Talman and Shadwick for second-order molecular properties and implemented into a Gaussian-basis-set, trial-vector algorithm. The only approximation involved, apart from the lack of correlation effects and the use of Gaussian-type basis functions, was the consistent use of the adiabatic approximation in the exchange kernel and in the linear response function. The static and dynamic polarizabilities and their anisotropy predicted by the TDDFT with exact exchange (TDOEP) agree accurately with the corresponding values from time-dependent Hartree-Fock theory, the exact-exchange counterpart in the wave function theory. The TDOEP is free from the nonphysical asymptotic decay of the exchange potential of most conventional density functionals or from any other manifestations of the incomplete cancellation of the self-interaction energy. The systematic overestimation of the absolute values and dispersion of polarizabilities that plagues most conventional TDDFT cannot be seen in the TDOEP

  3. Theoretical modeling of the electronic structure and exchange interactions in a Cu(II)Pc one-dimensional chain

    Science.gov (United States)

    Wu, Wei; Fisher, A. J.; Harrison, N. M.

    2011-07-01

    We calculate the electronic structure and exchange interactions in a copper(II)phthalocyanine [Cu(II)Pc] crystal as a one-dimensional molecular chain using hybrid exchange density functional theory (DFT). In addition, the intermolecular exchange interactions are also calculated in a molecular dimer using Green’s function perturbation theory (GFPT) to illustrate the underlying physics. We find that the exchange interactions depend strongly on the stacking angle, but weakly on the sliding angle (defined in the text). The hybrid DFT calculations also provide an insight into the electronic structure of the Cu(II)Pc molecular chain and demonstrate that on-site electron correlations have a significant effect on the nature of the ground state, the band gap, and magnetic excitations. The exchange interactions predicted by our DFT calculations and GFPT calculations agree qualitatively with the recent experimental results on newly found η-Cu(II)Pc and the previous results for the α and β phases. This work provides a reliable theoretical basis for the further application of Cu(II)Pc to molecular spintronics and organic-based quantum information processing.

  4. Semi-Local DFT Functionals with Exact-Exchange-Like Features: Beyond the AK13

    Science.gov (United States)

    Armiento, Rickard

    The Armiento-Kümmel functional from 2013 (AK13) is a non-empirical semi-local exchange functional on generalized gradient approximation form (GGA) in Kohn-Sham (KS) density functional theory (DFT). Recent works have established that AK13 gives improved electronic-structure exchange features over other semi-local methods, with a qualitatively improved orbital description and band structure. For example, the Kohn-Sham band gap is greatly extended, as it is for exact exchange. This talk outlines recent efforts towards new exchange-correlation functionals based on, and extending, the AK13 design ideas. The aim is to improve the quantitative accuracy, the description of energetics, and to address other issues found with the original formulation. Swedish e-Science Research Centre (SeRC).

  5. Dielectric Matrix Formulation of Correlation Energies in the Random Phase Approximation: Inclusion of Exchange Effects.

    Science.gov (United States)

    Mussard, Bastien; Rocca, Dario; Jansen, Georg; Ángyán, János G

    2016-05-10

    Starting from the general expression for the ground state correlation energy in the adiabatic-connection fluctuation-dissipation theorem (ACFDT) framework, it is shown that the dielectric matrix formulation, which is usually applied to calculate the direct random phase approximation (dRPA) correlation energy, can be used for alternative RPA expressions including exchange effects. Within this famework, the ACFDT analog of the second order screened exchange (SOSEX) approximation leads to a logarithmic formula for the correlation energy similar to the direct RPA expression. Alternatively, the contribution of the exchange can be included in the kernel used to evaluate the response functions. In this case, the use of an approximate kernel is crucial to simplify the formalism and to obtain a correlation energy in logarithmic form. Technical details of the implementation of these methods are discussed, and it is shown that one can take advantage of density fitting or Cholesky decomposition techniques to improve the computational efficiency; a discussion on the numerical quadrature made on the frequency variable is also provided. A series of test calculations on atomic correlation energies and molecular reaction energies shows that exchange effects are instrumental for improvement over direct RPA results.

  6. Off-shell pairing correlations from meson-exchange theory of nuclear forces

    International Nuclear Information System (INIS)

    Sedrakian, Armen

    2003-01-01

    We develop a model of off-mass-shell pairing correlations in nuclear systems, which is based on the meson-exchange picture of nuclear interactions. The temporal retardations in the model are generated by the Fock-exchange diagrams. The kernel of the complex gap equation for baryons is related to the in-medium spectral function of mesons, which is evaluated nonperturbatively in the random phase approximation. The model is applied to the low-density neutron matter in neutron star crusts by separating the interaction into a long-range one-pion-exchange component and a short-range component parametrized in terms of Landau Fermi liquid parameters. The resulting Eliashberg-type coupled nonlinear integral equations are solved by an iterative procedure. We find that the self-energies extend to off-shell energies of the order of several tens of MeV. At low energies the damping of the neutron pair correlations due to the coupling to the pionic modes is small, but becomes increasingly important as the energy is increased. We discuss an improved quasiclassical approximation under which the numerical solutions are obtained

  7. Hybrid empirical mode decomposition- ARIMA for forecasting exchange rates

    Science.gov (United States)

    Abadan, Siti Sarah; Shabri, Ani; Ismail, Shuhaida

    2015-02-01

    This paper studied the forecasting of monthly Malaysian Ringgit (MYR)/ United State Dollar (USD) exchange rates using the hybrid of two methods which are the empirical model decomposition (EMD) and the autoregressive integrated moving average (ARIMA). MYR is pegged to USD during the Asian financial crisis causing the exchange rates are fixed to 3.800 from 2nd of September 1998 until 21st of July 2005. Thus, the chosen data in this paper is the post-July 2005 data, starting from August 2005 to July 2010. The comparative study using root mean square error (RMSE) and mean absolute error (MAE) showed that the EMD-ARIMA outperformed the single-ARIMA and the random walk benchmark model.

  8. Proton Conductive Channel Optimization in Methanol Resistive Hybrid Hyperbranched Polyamide Proton Exchange Membrane

    Directory of Open Access Journals (Sweden)

    Liying Ma

    2017-12-01

    Full Text Available Based on a previously developed polyamide proton conductive macromolecule, the nano-scale structure of the self-assembled proton conductive channels (PCCs is adjusted via enlarging the nano-scale pore size within the macromolecules. Hyperbranched polyamide macromolecules with different size are synthesized from different monomers to tune the nano-scale pore size within the macromolecules, and a series of hybrid membranes are prepared from these two micromoles to optimize the PCC structure in the proton exchange membrane. The optimized membrane exhibits methanol permeability low to 2.2 × 10−7 cm2/s, while the proton conductivity of the hybrid membrane can reach 0.25 S/cm at 80 °C, which was much higher than the value of the Nafion 117 membrane (0.192 S/cm. By considering the mechanical, dimensional, and the thermal properties, the hybrid hyperbranched polyamide proton exchange membrane (PEM exhibits promising application potential in direct methanol fuel cells (DMFC.

  9. Spin-density functional for exchange anisotropic Heisenberg model

    International Nuclear Information System (INIS)

    Prata, G.N.; Penteado, P.H.; Souza, F.C.; Libero, Valter L.

    2009-01-01

    Ground-state energies for antiferromagnetic Heisenberg models with exchange anisotropy are estimated by means of a local-spin approximation made in the context of the density functional theory. Correlation energy is obtained using the non-linear spin-wave theory for homogeneous systems from which the spin functional is built. Although applicable to chains of any size, the results are shown for small number of sites, to exhibit finite-size effects and allow comparison with exact-numerical data from direct diagonalization of small chains.

  10. Exchanging and Storing Energy. Reducing Energy Demand through Heat Exchange between Functions and Temporary Storage

    Energy Technology Data Exchange (ETDEWEB)

    Sillem, E.

    2011-06-15

    As typical office buildings from the nineties have large heating and cooling installations to provide heat or cold wherever and whenever needed, more recent office buildings have almost no demand for heating due to high internal heat loads caused by people, lighting and office appliances and because of the great thermal qualities of the contemporary building envelope. However, these buildings still have vast cooling units to cool down servers and other energy consuming installations. At the same time other functions such as dwellings, swimming pools, sporting facilities, archives and museums still need to be heated most of the year. In the current building market there is an increasing demand for mixed-use buildings or so called hybrid buildings. The Science Business Centre is no different and houses a conference centre, offices, a museum, archives, an exhibition space and a restaurant. From the initial program brief it seemed that the building will simultaneously house functions that need cooling most of the year and functions that will need to be heated the majority of the year. Can this building be equipped with a 'micro heating and cooling network' and where necessary temporarily store energy? With this idea a research proposal was formulated. How can the demand for heating and cooling of the Science Business Centre be reduced by using energy exchange between different kinds of functions and by temporarily storing energy? In conclusion the research led to: four optimized installation concepts; short term energy storage in pavilion concept and museum; energy exchange between the restaurant and archives; energy exchange between the server space and the offices; the majority of heat and cold will be extracted from the soil (long term energy storage); the access heat will be generated by the energy roof; PV cells from the energy roof power all climate installations; a total energy plan for the Science Business Centre; a systematic approach for exchanging

  11. Improving Rydberg Excitations within Time-Dependent Density Functional Theory with Generalized Gradient Approximations: The Exchange-Enhancement-for-Large-Gradient Scheme.

    Science.gov (United States)

    Li, Shaohong L; Truhlar, Donald G

    2015-07-14

    Time-dependent density functional theory (TDDFT) with conventional local and hybrid functionals such as the local and hybrid generalized gradient approximations (GGA) seriously underestimates the excitation energies of Rydberg states, which limits its usefulness for applications such as spectroscopy and photochemistry. We present here a scheme that modifies the exchange-enhancement factor to improve GGA functionals for Rydberg excitations within the TDDFT framework while retaining their accuracy for valence excitations and for the thermochemical energetics calculated by ground-state density functional theory. The scheme is applied to a popular hybrid GGA functional and tested on data sets of valence and Rydberg excitations and atomization energies, and the results are encouraging. The scheme is simple and flexible. It can be used to correct existing functionals, and it can also be used as a strategy for the development of new functionals.

  12. Hexagonalization of correlation functions

    Energy Technology Data Exchange (ETDEWEB)

    Fleury, Thiago [Instituto de Física Teórica, UNESP - University Estadual Paulista,ICTP South American Institute for Fundamental Research,Rua Dr. Bento Teobaldo Ferraz 271, 01140-070, São Paulo, SP (Brazil); Komatsu, Shota [Perimeter Institute for Theoretical Physics,31 Caroline St N Waterloo, Ontario N2L 2Y5 (Canada)

    2017-01-30

    We propose a nonperturbative framework to study general correlation functions of single-trace operators in N=4 supersymmetric Yang-Mills theory at large N. The basic strategy is to decompose them into fundamental building blocks called the hexagon form factors, which were introduced earlier to study structure constants using integrability. The decomposition is akin to a triangulation of a Riemann surface, and we thus call it hexagonalization. We propose a set of rules to glue the hexagons together based on symmetry, which naturally incorporate the dependence on the conformal and the R-symmetry cross ratios. Our method is conceptually different from the conventional operator product expansion and automatically takes into account multi-trace operators exchanged in OPE channels. To illustrate the idea in simple set-ups, we compute four-point functions of BPS operators of arbitrary lengths and correlation functions of one Konishi operator and three short BPS operators, all at one loop. In all cases, the results are in perfect agreement with the perturbative data. We also suggest that our method can be a useful tool to study conformal integrals, and show it explicitly for the case of ladder integrals.

  13. Alternative separation of exchange and correlation energies in range-separated density-functional perturbation theory

    DEFF Research Database (Denmark)

    Cornaton, Y.; Stoyanova, A.; Jensen, Hans Jørgen Aagaard

    2013-01-01

    of the noninteracting Kohn-Sham one. When second-order corrections to the density are neglected, the energy expression reduces to a range-separated double-hybrid (RSDH) type of functional, RSDHf, where "f" stands for "full-range integrals" as the regular full-range interaction appears explicitly in the energy...

  14. Patching the Exchange-Correlation Potential in Density Functional Theory.

    Science.gov (United States)

    Huang, Chen

    2016-05-10

    A method for directly patching exchange-correlation (XC) potentials in materials is derived. The electron density of a system is partitioned into subsystem densities by dividing its Kohn-Sham (KS) potential among the subsystems. Inside each subsystem, its projected KS potential is required to become the total system's KS potential. This requirement, together with the nearsightedness principle of electronic matters, ensures that the electronic structures inside subsystems can be good approximations to the total system's electronic structure. The nearsightedness principle also ensures that subsystem densities could be well localized in their regions, making it possible to use high-level methods to invert the XC potentials for subsystem densities. Two XC patching methods are developed. In the local XC patching method, the total system's XC potential is improved in the cluster region. We show that the coupling between a cluster and its environment is important for achieving a fast convergence of the electronic structure in the cluster region. In the global XC patching method, we discuss how to patch the subsystem XC potentials to construct the XC potential in the total system, aiming to scale up high-level quantum mechanics simulations of materials. Proof-of-principle examples are given.

  15. Approximating the Shifted Hartree-Exchange-Correlation Potential in Direct Energy Kohn-Sham Theory.

    Science.gov (United States)

    Sharpe, Daniel J; Levy, Mel; Tozer, David J

    2018-02-13

    Levy and Zahariev [Phys. Rev. Lett. 113 113002 (2014)] have proposed a new approach for performing density functional theory calculations, termed direct energy Kohn-Sham (DEKS) theory. In this approach, the electronic energy equals the sum of orbital energies, obtained from Kohn-Sham-like orbital equations involving a shifted Hartree-exchange-correlation potential, which must be approximated. In the present study, density scaling homogeneity considerations are used to facilitate DEKS calculations on a series of atoms and molecules, leading to three nonlocal approximations to the shifted potential. The first two rely on preliminary Kohn-Sham calculations using a standard generalized gradient approximation (GGA) exchange-correlation functional and the results illustrate the benefit of describing the dominant Hartree component of the shift exactly. A uniform electron gas analysis is used to eliminate the need for these preliminary Kohn-Sham calculations, leading to a potential with an unconventional form that yields encouraging results, providing strong motivation for further research in DEKS theory.

  16. Method of vacuum correlation functions: Results and prospects

    International Nuclear Information System (INIS)

    Badalian, A. M.; Simonov, Yu. A.; Shevchenko, V. I.

    2006-01-01

    Basic results obtained within the QCD method of vacuum correlation functions over the past 20 years in the context of investigations into strong-interaction physics at the Institute of Theoretical and Experimental Physics (ITEP, Moscow) are formulated Emphasis is placed primarily on the prospects of the general theory developed within QCD by employing both nonperturbative and perturbative methods. On the basis of ab initio arguments, it is shown that the lowest two field correlation functions play a dominant role in QCD dynamics. A quantitative theory of confinement and deconfinement, as well as of the spectra of light and heavy quarkonia, glueballs, and hybrids, is given in terms of these two correlation functions. Perturbation theory in a nonperturbative vacuum (background perturbation theory) plays a significant role, not possessing drawbacks of conventional perturbation theory and leading to the infrared freezing of the coupling constant α s

  17. Electronic structure modeling of InAs/GaSb superlattices with hybrid density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Garwood, Tristan [Univ. of New Mexico, Albuquerque, NM (United States). Center for High Technology Materials; Modine, Normand A. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Krishna, S. [Univ. of New Mexico, Albuquerque, NM (United States). Center for High Technology Materials

    2016-12-18

    The application of first-principles calculations holds promise for greatly improving our understanding of semiconductor superlattices. By developing a procedure to accurately predict band gaps using hybrid density functional theory, it lays the groundwork for future studies investigating more nuanced properties of these structures. Our approach allows a priori prediction of the properties of SLS structures using only the band gaps of the constituent materials. Furthermore, it should enable direct investigation of the effects of interface structure, e.g., intermixing or ordering at the interface, on SLS properties. In this paper, we present band gap data for various InAs/GaSb type-II superlattice structures calculated using the generalized Kohn-Sham formulation of density functional theory. A PBE0-type hybrid functional was used, and the portion of the exact exchange was tuned to fit the band gaps of the binary compounds InAs and GaSb with the best agreement to bulk experimental values obtained with 18% of the exact exchange. The heterostructures considered in this study are 6 monolayer (ML) InAs/6 ML GaSb, 8 ML InAs/8 ML GaSb and 10 ML InAs/10 ML GaSb with deviations from the experimental band gaps ranging from 3% to 11%.

  18. Bioinorganic Chemistry Modeled with the TPSSh Density Functional

    DEFF Research Database (Denmark)

    Kepp, Kasper Planeta

    2008-01-01

    functionals such as B3LYP and BP86. TPSSh gives a slope of 0.99 upon linear fitting to experimental bond energies, whereas B3LYP and BP86, representing 20% and 0% exact exchange, respectively, give linear fits with slopes of 0.91 and 1.07. Thus, TPSSh eliminates the large systematic component of the error...... functional provides energies approximately halfway between nonhybrids BP86 and TPSS, and 20% exact exchange hybrid B3LYP: Thus, a linear correlation between the amount of exact exchange and the numeric value of the reaction energy is observed in all these cases. For these reasons, TPSSh stands out as a most...

  19. The exchange of correlated pions and kaons in the baryon-baryon interaction

    International Nuclear Information System (INIS)

    Reuber, A.G.

    1995-09-01

    The exchange of two correlated pions or kaons provides the main part of the intermediate-range attraction between two baryons. In this work, a dynamical model for correlated two-pion and two-kaon exchange in the baryon-baryon interaction is presented, both in the scalar-isoscalar (σ) and the vector-isovector (ρ) channel. The contribution of correlated ππ and K anti K exchange is derived from the amplitudes for the transition of a baryon-antibaryon state (B anti B') to a ππ or K anti K state in the pseudophysical region by applying dispersion theory and unitarity. For the B anti B'→ππ, K anti K amplitudes a microscopic model is constructed, which is based on the hadron-exchange picture. The Born terms include contributions from baryon-exchange as well as ρ-pole diagrams. The correlations between the two pseudoscalar mesons are taken into account exactly by means of ππ-K anti K amplitudes derived likewise from a meson-exchange model, which is in line with the empirical ππ data. The parameters of the B anti B'→ππ, K anti K model, which are related to each other by the assumption of SU(3) symmetry, are determined by the adjustment to the quasiempirical N anti N→ππ amplitudes in the pseudophysical region. It is found that correlated K anti K exchange being negligible in the NN interaction plays an important role in the σ-channel for baryon-baryon states with non-vanishing strangeness. The strength of correlated ππ plus K anti K exchange in the σ-channel decreases with the strangeness of the baryon-baryon system becoming more negative. Due to the admixture of baryon-exchange processes to the SU(3)-symmetric ρ-pole contributions the results for correlated ππ-exchange in the vector-isovector channel deviate from what is expected in the naive SU(3) picture for genuine ρ-exchange. (orig.)

  20. Assessment of density-functional approximations: Long-range correlations and self-interaction effects

    International Nuclear Information System (INIS)

    Jung, J.; Alvarellos, J.E.; Garcia-Gonzalez, P.; Godby, R.W.

    2004-01-01

    The complex nature of electron-electron correlations is made manifest in the very simple but nontrivial problem of two electrons confined within a sphere. The description of highly nonlocal correlation and self-interaction effects by widely used local and semilocal exchange-correlation energy density functionals is shown to be unsatisfactory in most cases. Even the best such functionals exhibit significant errors in the Kohn-Sham potentials and density profiles

  1. A density functional theory study of the influence of exchange-correlation functionals on the properties of FeAs.

    Science.gov (United States)

    Griffin, Sinéad M; Spaldin, Nicola A

    2017-06-01

    We use density functional theory within the local density approximation (LDA), LDA  +  U, generalised gradient approximation (GGA), GGA  +  U, and hybrid-functional methods to calculate the properties of iron monoarsenide. FeAs, which forms in the MnP structure, is of current interest for potential spintronic applications as well as being the parent compound for the pnictide superconductors. We compare the calculated structural, magnetic and electronic properties obtained using the different functionals to each other and to experiment, and investigate the origin of a recently reported magnetic spiral. Our results indicate the appropriateness or otherwise of the various functionals for describing FeAs and the related Fe-pnictide superconductors.

  2. Exact Time-Dependent Exchange-Correlation Potential in Electron Scattering Processes

    Science.gov (United States)

    Suzuki, Yasumitsu; Lacombe, Lionel; Watanabe, Kazuyuki; Maitra, Neepa T.

    2017-12-01

    We identify peak and valley structures in the exact exchange-correlation potential of time-dependent density functional theory that are crucial for time-resolved electron scattering in a model one-dimensional system. These structures are completely missed by adiabatic approximations that, consequently, significantly underestimate the scattering probability. A recently proposed nonadiabatic approximation is shown to correctly capture the approach of the electron to the target when the initial Kohn-Sham state is chosen judiciously, and it is more accurate than standard adiabatic functionals but ultimately fails to accurately capture reflection. These results may explain the underestimation of scattering probabilities in some recent studies on molecules and surfaces.

  3. Experimental temperature analysis of simple & hybrid earth air tunnel heat exchanger in series connection at Bikaner Rajasthan India

    Science.gov (United States)

    Jakhar, O. P.; Sharma, Chandra Shekhar; Kukana, Rajendra

    2018-05-01

    The Earth Air Tunnel Heat Exchanger System is a passive air-conditioning system which has no side effect on earth climate and produces better cooling effect and heating effect comfortable to human body. It produces heating effect in winter and cooling effect in summer with the minimum power consumption of energy as compare to other air-conditioning devices. In this research paper Temperature Analysis was done on the two systems of Earth Air Tunnel Heat Exchanger experimentally for summer cooling purpose. Both the system was installed at Mechanical Engineering Department Government Engineering College Bikaner Rajasthan India. Experimental results concludes that the Average Air Temperature Difference was found as 11.00° C and 16.27° C for the Simple and Hybrid Earth Air Tunnel Heat Exchanger in Series Connection System respectively. The Maximum Air Temperature Difference was found as 18.10° C and 23.70° C for the Simple and Hybrid Earth Air Tunnel Heat Exchanger in Series Connection System respectively. The Minimum Air Temperature Difference was found as 5.20° C and 11.70° C for the Simple and Hybrid Earth Air Tunnel Heat Exchanger in Series Connection System respectively.

  4. Non-local exchange correlation functionals impact on the structural, electronic and optical properties of III-V arsenides

    KAUST Repository

    Anua, N. Najwa; Ahmed, Rashid; Shaari, Amiruddin; Saeed, Mohammad Alam; Ul Haq, Bakhtiar; Goumri-Said, Souraya

    2013-01-01

    our electronic bandstructure calculations at the level of mBJ-LDA potential show considerable improvements over the other XC functionals, even the sX-LDA hybrid functional. We report also the optical properties within mBJ potential, which show a nice

  5. A hybrid system using a regenerative electrochemical cycle to harvest waste heat from the proton exchange membrane fuel cell

    International Nuclear Information System (INIS)

    Long, Rui; Li, Baode; Liu, Zhichun; Liu, Wei

    2015-01-01

    A new hybrid system consisting of a PEMFC (proton exchange membrane fuel cell) subsystem and a TREC (thermally regenerative electrochemical cycle) subsystem is proposed to convert the waste heat produced by the PEMFC system into electricity. The performance of the hybrid system and its corresponding subsystems is analyzed. Results reveal that there exists optimal current densities of the PEMFC and TREC systems leading to the maximum power output of the hybrid system. With the maximum power output as the objective function, an optimization of the hybrid system based on genetic algorithm method is conducted under different operating temperatures of the PEMFC subsystem. The power output of the hybrid system is 6.85%–20.59% larger than that of the PEMFC subsystem. And the total electrical efficiency is improved by 2.74%–8.27%. The corresponding electrical efficiency of the TREC is 4.56%–13.81%. The hybrid system proposed in this paper could contribute to utilizing the fuel energy more efficiently and sufficiently. - Highlights: • A hybrid power system consisting of a PEMFC and a TREC subsystems is proposed. • Parameters' impacts on performance of the hybrid system have been analyzed. • The maximum power output of the hybrid system is investigated based on genetic algorithm. • Total power output of the hybrid system is 7.63%–18.84% larger than that of the PEMFC subsystem.

  6. Description of plasmon-like band in silver clusters: the importance of the long-range Hartree-Fock exchange in time-dependent density-functional theory simulations.

    Science.gov (United States)

    Rabilloud, Franck

    2014-10-14

    Absorption spectra of Ag20 and Ag55(q) (q = +1, -3) nanoclusters are investigated in the framework of the time-dependent density functional theory in order to analyse the role of the d electrons in plasmon-like band of silver clusters. The description of the plasmon-like band from calculations using density functionals containing an amount of Hartree-Fock exchange at long range, namely, hybrid and range-separated hybrid (RSH) density functionals, is in good agreement with the classical interpretation of the plasmon-like structure as a collective excitation of valence s-electrons. In contrast, using local or semi-local exchange functionals (generalized gradient approximations (GGAs) or meta-GGAs) leads to a strong overestimation of the role of d electrons in the plasmon-like band. The semi-local asymptotically corrected model potentials also describe the plasmon as mainly associated to d electrons, though calculated spectra are in fairly good agreement with those calculated using the RSH scheme. Our analysis shows that a portion of non-local exchange modifies the description of the plasmon-like band.

  7. Optimizing the Structure of Tetracyanoplatinate (II): A Comparison of Relativistic Density Functional Theory Methods

    DEFF Research Database (Denmark)

    Dohn, Asmus Ougaard; Møller, Klaus Braagaard; Sauer, Stephan P. A.

    2013-01-01

    is almost quantitatively reproduced in the ZORA and ECP calculations. In addition, the effect of the exchange-correlation functional and one-electron basis set was studied by employing the two generalized gradient approximation (GGA) functionals, BLYP and PBE, as well as their hybrid version B3LYP and PBE0...

  8. Enhancement of exchange coupling interaction of NdFeB/MnBi hybrid magnets

    Science.gov (United States)

    Nguyen, Truong Xuan; Nguyen, Khanh Van; Nguyen, Vuong Van

    2018-03-01

    MnBi ribbons were fabricated by melt - spinning with subsequent annealing. The MnBi ribbons were ground and mixed with NdFeB commercial Magnequench powders (MQA). The hybrid powder mixtures were subjected thrice to the annealing and ball-milling route. The hybrid magnets (100 - x)NdFeB/xMnBi, x=0, 30, 40, 50 and 100 wt% were in-mold aligned in an 18 kOe magnetic field and warm compacted at 290 °C by 2000 psi uniaxial pressure for 10 min. An enhancement of the exchange coupling of NdFeB/MnBi hybrid magnets was obtained by optimizing the magnets' microstructures via annealing and ball-milling processes. The magnetic properties of prepared NdFeB/MnBi hybrid magnets were studied and discussed in details.

  9. Giant spin torque in hybrids with anisotropic p-d exchange interaction

    Science.gov (United States)

    Korenev, V. L.

    2014-03-01

    Control of magnetic domain wall movement by the spin-polarized current looks promising for creation of a new generation of magnetic memory devices. A necessary condition for this is the domain wall shift by a low-density current. Here, I show that a strongly anisotropic exchange interaction between mobile heavy holes and localized magnetic moments enormously increases the current-induced torque on the domain wall as compared to systems with isotropic exchange. This enables one to control the domain wall motion by current density 104 A/cm2 in ferromagnet/semiconductor hybrids. The experimental observation of the anisotropic torque will facilitate the integration of ferromagnetism into semiconductor electronics.

  10. Giant spin torque in hybrids with anisotropic p-d exchange interaction

    International Nuclear Information System (INIS)

    Korenev, V. L.

    2014-01-01

    Control of magnetic domain wall movement by the spin-polarized current looks promising for creation of a new generation of magnetic memory devices. A necessary condition for this is the domain wall shift by a low-density current. Here, I show that a strongly anisotropic exchange interaction between mobile heavy holes and localized magnetic moments enormously increases the current-induced torque on the domain wall as compared to systems with isotropic exchange. This enables one to control the domain wall motion by current density 10 4  A/cm 2 in ferromagnet/semiconductor hybrids. The experimental observation of the anisotropic torque will facilitate the integration of ferromagnetism into semiconductor electronics

  11. Direct measurement of the long-range p -d exchange coupling in a ferromagnet-semiconductor Co/CdMgTe/CdTe quantum well hybrid structure

    Science.gov (United States)

    Akimov, I. A.; Salewski, M.; Kalitukha, I. V.; Poltavtsev, S. V.; Debus, J.; Kudlacik, D.; Sapega, V. F.; Kopteva, N. E.; Kirstein, E.; Zhukov, E. A.; Yakovlev, D. R.; Karczewski, G.; Wiater, M.; Wojtowicz, T.; Korenev, V. L.; Kusrayev, Yu. G.; Bayer, M.

    2017-11-01

    The exchange interaction between magnetic ions and charge carriers in semiconductors is considered to be a prime tool for spin control. Here, we solve a long-standing problem by uniquely determining the magnitude of the long-range p -d exchange interaction in a ferromagnet-semiconductor (FM-SC) hybrid structure where a 10-nm-thick CdTe quantum well is separated from the FM Co layer by a CdMgTe barrier with a thickness on the order of 10 nm. The exchange interaction is manifested by the spin splitting of acceptor bound holes in the effective magnetic field induced by the FM. The exchange splitting is directly evaluated using spin-flip Raman scattering by analyzing the dependence of the Stokes shift ΔS on the external magnetic field B . We show that in a strong magnetic field, ΔS is a linear function of B with an offset of Δp d=50 -100 μ eV at zero field from the FM induced effective exchange field. On the other hand, the s -d exchange interaction between conduction band electrons and FM, as well as the p -d contribution for free valence band holes, are negligible. The results are well described by the model of indirect exchange interaction between acceptor bound holes in the CdTe quantum well and the FM layer mediated by elliptically polarized phonons in the hybrid structure.

  12. Apparent violation of the sum rule for exchange-correlation charges by generalized gradient approximations.

    Science.gov (United States)

    Kohut, Sviataslau V; Staroverov, Viktor N

    2013-10-28

    The exchange-correlation potential of Kohn-Sham density-functional theory, vXC(r), can be thought of as an electrostatic potential produced by the static charge distribution qXC(r) = -(1∕4π)∇(2)vXC(r). The total exchange-correlation charge, QXC = ∫qXC(r) dr, determines the rate of the asymptotic decay of vXC(r). If QXC ≠ 0, the potential falls off as QXC∕r; if QXC = 0, the decay is faster than coulombic. According to this rule, exchange-correlation potentials derived from standard generalized gradient approximations (GGAs) should have QXC = 0, but accurate numerical calculations give QXC ≠ 0. We resolve this paradox by showing that the charge density qXC(r) associated with every GGA consists of two types of contributions: a continuous distribution and point charges arising from the singularities of vXC(r) at each nucleus. Numerical integration of qXC(r) accounts for the continuous charge but misses the point charges. When the point-charge contributions are included, one obtains the correct QXC value. These findings provide an important caveat for attempts to devise asymptotically correct Kohn-Sham potentials by modeling the distribution qXC(r).

  13. Computer code MLCOSP for multiple-correlation and spectrum analysis with a hybrid computer

    International Nuclear Information System (INIS)

    Oguma, Ritsuo; Fujii, Yoshio; Usui, Hozumi; Watanabe, Koichi

    1975-10-01

    Usage of the computer code MLCOSP(Multiple Correlation and Spectrum) developed is described for a hybrid computer installed in JAERI Functions of the hybrid computer and its terminal devices are utilized ingeniously in the code to reduce complexity of the data handling which occurrs in analysis of the multivariable experimental data and to perform the analysis in perspective. Features of the code are as follows; Experimental data can be fed to the digital computer through the analog part of the hybrid computer by connecting with a data recorder. The computed results are displayed in figures, and hardcopies are taken when necessary. Series-messages to the code are shown on the terminal, so man-machine communication is possible. And further the data can be put in through a keyboard, so case study according to the results of analysis is possible. (auth.)

  14. Magneto-structural correlations in exchange coupled systems

    International Nuclear Information System (INIS)

    Willett, R.D.; Gatteschi, D.; Kahn, O.

    1985-01-01

    This book contains 19 chapters. Some of the chapter titles are: Optical Spectroscophy; The Basis of Spin-Hamiltonian Theory; Inelastic Neutorn Scattering From Clusters; Magneto-structural Correlations in Bioinorganic Chemistry; and Magnetic Exchange Interactions Propagated by Multi-Atom Bridges

  15. Locality of correlation in density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Burke, Kieron [Department of Chemistry, University of California, Irvine, California 92697 (United States); Cancio, Antonio [Department of Physics and Astronomy, Ball State University, Muncie, Indiana 47306 (United States); Gould, Tim [Qld Micro- and Nanotechnology Centre, Griffith University, Nathan, Qld 4111 (Australia); Pittalis, Stefano [CNR-Istituto di Nanoscienze, Via Campi 213A, I-41125 Modena (Italy)

    2016-08-07

    The Hohenberg-Kohn density functional was long ago shown to reduce to the Thomas-Fermi (TF) approximation in the non-relativistic semiclassical (or large-Z) limit for all matter, i.e., the kinetic energy becomes local. Exchange also becomes local in this limit. Numerical data on the correlation energy of atoms support the conjecture that this is also true for correlation, but much less relevant to atoms. We illustrate how expansions around a large particle number are equivalent to local density approximations and their strong relevance to density functional approximations. Analyzing highly accurate atomic correlation energies, we show that E{sub C} → −A{sub C} ZlnZ + B{sub C}Z as Z → ∞, where Z is the atomic number, A{sub C} is known, and we estimate B{sub C} to be about 37 mhartree. The local density approximation yields A{sub C} exactly, but a very incorrect value for B{sub C}, showing that the local approximation is less relevant for the correlation alone. This limit is a benchmark for the non-empirical construction of density functional approximations. We conjecture that, beyond atoms, the leading correction to the local density approximation in the large-Z limit generally takes this form, but with B{sub C} a functional of the TF density for the system. The implications for the construction of approximate density functionals are discussed.

  16. Oscillatory wake potential with exchange-correlation in plasmas

    Science.gov (United States)

    Khan, Arroj A.; Zeba, I.; Jamil, M.; Asif, M.

    2017-12-01

    The oscillatory wake potential of a moving test charge is studied in quantum dusty plasmas. The plasma system consisting of electrons, ions and negatively charged dust species is embedded in an ambient magnetic field. The modified equation of dispersion is derived using a Quantum Hydrodynamic Model for magnetized plasmas. The quantum effects are inculcated through Fermi degenerate pressure, the tunneling effect and exchange-correlation effects. The study of oscillatory wake is important to know the existence of silence zones in space and astrophysical objects as well as for crystal formation. The graphical description of the potential depicts the significance of the exchange and correlation effects arising through spin and other variables on the wake potential.

  17. Managing operations of plug-in hybrid electric vehicle (PHEV) exchange stations for use with a smart grid

    International Nuclear Information System (INIS)

    Nurre, Sarah G.; Bent, Russell; Pan, Feng; Sharkey, Thomas C.

    2014-01-01

    We consider a deterministic integer programming model for determining the optimal operations of multiple plug-in hybrid electric vehicle (PHEV) battery exchange stations over time. The operations include the number of batteries to charge, discharge, and exchange at each point in time over a set time horizon. We allow discharging of batteries back to the power grid, through vehicle-to-grid technology. We incorporate the exchange station's dependence on the power network, transportation network, and other exchange stations. The charging and discharging at these exchange stations lead to a greater amount of variability which creates a less predictable and flat power generation curve. We introduce and test three policies to smooth the power generation curve by balancing its load. Further, tests are conducted evaluating these policies while factoring wind energy into the power generation curve. These computational tests use realistic data and analysis of the results suggest general operating procedures for exchange stations and evaluate the effectiveness of these power flattening policies. - Highlights: • Model the operations of plug-in hybrid electric vehicle battery exchange stations. • Determine the optimal and general charging, discharging, and exchange operations. • Conclude that forced customer service levels are unnecessary with proper pricing. • Examine policies to reduce variability in power generation from PHEVs and wind. • Observe that strict constraints on exchange stations best reduce variability

  18. Detrended cross-correlation analysis on RMB exchange rate and Hang Seng China Enterprises Index

    Science.gov (United States)

    Ruan, Qingsong; Yang, Bingchan; Ma, Guofeng

    2017-02-01

    In this paper, we investigate the cross-correlations between the Hang Seng China Enterprises Index and RMB exchange markets on the basis of a cross-correlation statistic test and multifractal detrended cross-correlation analysis (MF-DCCA). MF-DCCA has, at best, serious limitations for most of the signals describing complex natural processes and often indicates multifractal cross-correlations when there are none. In order to prevent these false multifractal cross-correlations, we apply MFCCA to verify the cross-correlations. Qualitatively, we find that the return series of the Hang Seng China Enterprises Index and RMB exchange markets were, overall, significantly cross-correlated based on the statistical analysis. Quantitatively, we find that the cross-correlations between the stock index and RMB exchange markets were strongly multifractal, and the multifractal degree of the onshore RMB exchange markets was somewhat larger than the offshore RMB exchange markets. Moreover, we use the absolute return series to investigate and confirm the fact of multifractality. The results from the rolling windows show that the short-term cross-correlations between volatility series remain high.

  19. A hybrid measure-correlate-predict method for long-term wind condition assessment

    International Nuclear Information System (INIS)

    Zhang, Jie; Chowdhury, Souma; Messac, Achille; Hodge, Bri-Mathias

    2014-01-01

    Highlights: • A hybrid measure-correlate-predict (MCP) methodology with greater accuracy is developed. • Three sets of performance metrics are proposed to evaluate the hybrid MCP method. • Both wind speed and direction are considered in the hybrid MCP method. • The best combination of MCP algorithms is determined. • The developed hybrid MCP method is uniquely helpful for long-term wind resource assessment. - Abstract: This paper develops a hybrid measure-correlate-predict (MCP) strategy to assess long-term wind resource variations at a farm site. The hybrid MCP method uses recorded data from multiple reference stations to estimate long-term wind conditions at a target wind plant site with greater accuracy than is possible with data from a single reference station. The weight of each reference station in the hybrid strategy is determined by the (i) distance and (ii) elevation differences between the target farm site and each reference station. In this case, the wind data is divided into sectors according to the wind direction, and the MCP strategy is implemented for each wind direction sector separately. The applicability of the proposed hybrid strategy is investigated using five MCP methods: (i) the linear regression; (ii) the variance ratio; (iii) the Weibull scale; (iv) the artificial neural networks; and (v) the support vector regression. To implement the hybrid MCP methodology, we use hourly averaged wind data recorded at five stations in the state of Minnesota between 07-01-1996 and 06-30-2004. Three sets of performance metrics are used to evaluate the hybrid MCP method. The first set of metrics analyze the statistical performance, including the mean wind speed, wind speed variance, root mean square error, and mean absolute error. The second set of metrics evaluate the distribution of long-term wind speed; to this end, the Weibull distribution and the Multivariate and Multimodal Wind Distribution models are adopted. The third set of metrics analyze

  20. Parametric analysis of an irreversible proton exchange membrane fuel cell/absorption refrigerator hybrid system

    International Nuclear Information System (INIS)

    Yang, Puqing; Zhang, Houcheng

    2015-01-01

    A hybrid system mainly consisting of a PEMFC (proton exchange membrane fuel cell) and an absorption refrigerator is proposed, where the PEMFC directly converts the chemical energy contained in the hydrogen into electrical and thermal energies, and the thermal energy is transferred to drive the bottoming absorption refrigerator for cooling purpose. By considering the existing irreversible losses in the hybrid system, the operating current density region of the PEMFC permits the absorption refrigerator to exert its function is determined and the analytical expressions for the equivalent power output and efficiency of the hybrid system under different operating conditions are specified. Numerical calculations show that the equivalent maximum power density and the corresponding efficiency of the hybrid system can be respectively increased by 5.3% and 6.8% compared to that of the stand-alone PEMFC. Comprehensive parametric analyses are conducted to reveal the effects of the internal irreversibility of the absorption refrigerator, operating current density, operating temperature and operating pressure of the PEMFC, and some integrated parameters related to the thermodynamic losses on the performance of the hybrid system. The model presented in the paper is more general than previous study, and the results for some special cases can be directly derived from this paper. - Highlights: • A CHP system composed of a PEMFC and an absorption refrigerator is proposed. • Current density region enables the absorption refrigerator to work is determined. • Multiple irreversible losses in the system are analytically characterized. • Maximum power density and corresponding efficiency can be increased by 5.3% and 6.8%. • Effects of some designing and operating parameters on the performance are discussed

  1. Nonlinear electronic excitations in crystalline solids using meta-generalized gradient approximation and hybrid functional in time-dependent density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Shunsuke A. [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan); Taniguchi, Yasutaka [Center for Computational Science, University of Tsukuba, Tsukuba 305-8571 (Japan); Department of Medical and General Sciences, Nihon Institute of Medical Science, 1276 Shimogawara, Moroyama-Machi, Iruma-Gun, Saitama 350-0435 (Japan); Shinohara, Yasushi [Max Planck Institute of Microstructure Physics, 06120 Halle (Germany); Yabana, Kazuhiro [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan); Center for Computational Science, University of Tsukuba, Tsukuba 305-8571 (Japan)

    2015-12-14

    We develop methods to calculate electron dynamics in crystalline solids in real-time time-dependent density functional theory employing exchange-correlation potentials which reproduce band gap energies of dielectrics; a meta-generalized gradient approximation was proposed by Tran and Blaha [Phys. Rev. Lett. 102, 226401 (2009)] (TBm-BJ) and a hybrid functional was proposed by Heyd, Scuseria, and Ernzerhof [J. Chem. Phys. 118, 8207 (2003)] (HSE). In time evolution calculations employing the TB-mBJ potential, we have found it necessary to adopt the predictor-corrector step for a stable time evolution. We have developed a method to evaluate electronic excitation energy without referring to the energy functional which is unknown for the TB-mBJ potential. For the HSE functional, we have developed a method for the operation of the Fock-like term in Fourier space to facilitate efficient use of massive parallel computers equipped with graphic processing units. We compare electronic excitations in silicon and germanium induced by femtosecond laser pulses using the TB-mBJ, HSE, and a simple local density approximation (LDA). At low laser intensities, electronic excitations are found to be sensitive to the band gap energy: they are close to each other using TB-mBJ and HSE and are much smaller in LDA. At high laser intensities close to the damage threshold, electronic excitation energies do not differ much among the three cases.

  2. Giant spin torque in hybrids with anisotropic p-d exchange interaction

    Energy Technology Data Exchange (ETDEWEB)

    Korenev, V. L., E-mail: korenev@orient.ioffe.ru [A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia and Experimentelle Physik 2, Technische Universitat Dortmund, D-44227 Dortmund (Germany)

    2014-03-03

    Control of magnetic domain wall movement by the spin-polarized current looks promising for creation of a new generation of magnetic memory devices. A necessary condition for this is the domain wall shift by a low-density current. Here, I show that a strongly anisotropic exchange interaction between mobile heavy holes and localized magnetic moments enormously increases the current-induced torque on the domain wall as compared to systems with isotropic exchange. This enables one to control the domain wall motion by current density 10{sup 4} A/cm{sup 2} in ferromagnet/semiconductor hybrids. The experimental observation of the anisotropic torque will facilitate the integration of ferromagnetism into semiconductor electronics.

  3. Plasmon dispersion and dynamic exchange-correlation potential from two-pair excitations in degenerate plasmas

    International Nuclear Information System (INIS)

    Boehm, H.M.; Conti, S.; Tosi, M.P.

    1995-11-01

    Electron energy loss experiments have shown a rapid softening of the bulk plasmon dispersion across the series of the alkali metals. Motivated by these observations, we reconsider the evaluation of the dynamic, long-wavelength exchange-correlation potential f xc (ω) in the electron fluid, which is of interest for applications in time-dependent density functional theory. The value of Re[f xc (ω pl )] at the plasma frequency ω pl determines the exchange-correlation contribution to the leading plasmon dispersion coefficient in the homogeneous electron fluid. Whereas an interpolation scheme originally proposed by Gross and Kohn assumes a monotonic increase of Re[f xc (ω) - f xc (0)] across the plasma frequency, we examine the possibility of strongly non-monotonic behaviour arising from a resonance process between plasmons and two-pair excitations. This process is evaluated with the help of sum rules and selfconsistency requirements with a single-pole approximation of the dielectric function. The cases of a fermion plasma and of a boson plasma are treated in parallel and the reliability of the results for the fermion plasma at low coupling is tested by calculations within a random phase approximation for the dielectric function. In all cases it is found that the resonance process accumulates oscillator strength in the neighbourhood of 2ω pl , thus decreasing the value of Re[f xc (ω pl )] below the static value f xc (0) fixed by the compressibility sum rule. Although this lowering does not suffice to account by itself for the measured plasmon dispersion coefficient in the low-density alkali metals, our results provide useful input for combined band-structure and exchange-correlation calculations. (author). 40 refs, 9 figs, 2 tabs

  4. Explicitly-correlated ring-coupled-cluster-doubles theory: Including exchange for computations on closed-shell systems

    Energy Technology Data Exchange (ETDEWEB)

    Hehn, Anna-Sophia; Holzer, Christof; Klopper, Wim, E-mail: klopper@kit.edu

    2016-11-10

    Highlights: • Ring-coupled-cluster-doubles approach now implemented with exchange terms. • Ring-coupled-cluster-doubles approach now implemented with F12 functions. • Szabo–Ostlund scheme (SO2) implemented for use in SAPT. • Fast convergence to the limit of a complete basis. • Implementation in the TURBOMOLE program system. - Abstract: Random-phase-approximation (RPA) methods have proven to be powerful tools in electronic-structure theory, being non-empirical, computationally efficient and broadly applicable to a variety of molecular systems including small-gap systems, transition-metal compounds and dispersion-dominated complexes. Applications are however hindered due to the slow basis-set convergence of the electron-correlation energy with the one-electron basis. As a remedy, we present approximate explicitly-correlated RPA approaches based on the ring-coupled-cluster-doubles formulation including exchange contributions. Test calculations demonstrate that the basis-set convergence of correlation energies is drastically accelerated through the explicitly-correlated approach, reaching 99% of the basis-set limit with triple-zeta basis sets. When implemented in close analogy to early work by Szabo and Ostlund [36], the new explicitly-correlated ring-coupled-cluster-doubles approach including exchange has the perspective to become a valuable tool in the framework of symmetry-adapted perturbation theory (SAPT) for the computation of dispersion energies of molecular complexes of weakly interacting closed-shell systems.

  5. Efficient, approximate and parallel Hartree-Fock and hybrid DFT calculations. A 'chain-of-spheres' algorithm for the Hartree-Fock exchange

    International Nuclear Information System (INIS)

    Neese, Frank; Wennmohs, Frank; Hansen, Andreas; Becker, Ute

    2009-01-01

    In this paper, the possibility is explored to speed up Hartree-Fock and hybrid density functional calculations by forming the Coulomb and exchange parts of the Fock matrix by different approximations. For the Coulomb part the previously introduced Split-RI-J variant (F. Neese, J. Comput. Chem. 24 (2003) 1740) of the well-known 'density fitting' approximation is used. The exchange part is formed by semi-numerical integration techniques that are closely related to Friesner's pioneering pseudo-spectral approach. Our potentially linear scaling realization of this algorithm is called the 'chain-of-spheres exchange' (COSX). A combination of semi-numerical integration and density fitting is also proposed. Both Split-RI-J and COSX scale very well with the highest angular momentum in the basis sets. It is shown that for extended basis sets speed-ups of up to two orders of magnitude compared to traditional implementations can be obtained in this way. Total energies are reproduced with an average error of <0.3 kcal/mol as determined from extended test calculations with various basis sets on a set of 26 molecules with 20-200 atoms and up to 2000 basis functions. Reaction energies agree to within 0.2 kcal/mol (Hartree-Fock) or 0.05 kcal/mol (hybrid DFT) with the canonical values. The COSX algorithm parallelizes with a speedup of 8.6 observed for 10 processes. Minimum energy geometries differ by less than 0.3 pm in the bond distances and 0.5 deg. in the bond angels from their canonical values. These developments enable highly efficient and accurate self-consistent field calculations including nonlocal Hartree-Fock exchange for large molecules. In combination with the RI-MP2 method and large basis sets, second-order many body perturbation energies can be obtained for medium sized molecules with unprecedented efficiency. The algorithms are implemented into the ORCA electronic structure system

  6. Neutrinoless ββ decay mediated by the exchange of light and heavy neutrinos: the role of nuclear structure correlations

    Science.gov (United States)

    Menéndez, J.

    2018-01-01

    Neutrinoless β β decay nuclear matrix elements calculated with the shell model and energy-density functional theory typically disagree by more than a factor of two in the standard scenario of light-neutrino exchange. In contrast, for a decay mediated by sterile heavy neutrinos the deviations are reduced to about 50%, an uncertainty similar to the one due to short-range effects. We compare matrix elements in the light- and heavy-neutrino-exchange channels, exploring the radial, momentum transfer and angular momentum-parity matrix element distributions, and considering transitions that involve correlated and uncorrelated nuclear states. We argue that the shorter-range heavy-neutrino exchange is less sensitive to collective nuclear correlations, and that discrepancies in matrix elements are mostly due to the treatment of long-range correlations in many-body calculations. Our analysis supports previous studies suggesting that isoscalar pairing correlations, which affect mostly the longer-range part of the neutrinoless β β decay operator, are partially responsible for the differences between nuclear matrix elements in the standard light-neutrino-exchange mechanism.

  7. The shortcomings of semi-local and hybrid functionals: what we can learn from surface science studies

    International Nuclear Information System (INIS)

    Stroppa, A; Kresse, G

    2008-01-01

    A study of the adsorption of CO on late 4d and 5d transition metal (111) surfaces (Ru, Rh, Pd, Ag, Os, Ir and Pt) considering atop and hollow site adsorption is presented. The applied functionals include the gradient-corrected Perdew-Burke-Ernzerhof (PBE) and Becke-Lee-Yang-Parr (BLYP) functionals, and the corresponding hybrid Hartree-Fock density functionals HSE and B3LYP. We find that PBE-based hybrid functionals (specifically HSE) yield, with the exception of Pt, the correct site order on all considered metals, but they also considerably overestimate the adsorption energies compared to experiment. On the other hand, the semi-local BLYP functional and the corresponding hybrid functional B3LYP yield very satisfactory adsorption energies and the correct adsorption site for all surfaces. We are thus faced with a Procrustean problem: the B3LYP and BLYP functionals seem to be the overall best choice for describing adsorption on metal surfaces, but they simultaneously fail to account well for the properties of the metal, vastly overestimating the equilibrium volume and underestimating the atomization energies. Setting out from these observations, general conclusions are drawn on the relative merits and drawbacks of various semi-local and hybrid functionals. The discussion includes a revised version of the PBE functional specifically optimized for bulk properties and surface energies (PBEsol), a revised version of the PBE functional specifically optimized to predict accurate adsorption energies (rPBE), as well as the aforementioned BLYP functional. We conclude that no semi-local functional is capable of describing all aspects properly, and including non-local exchange also only improves some but worsens other properties

  8. Ion-Exchange-Induced Selective Etching for the Synthesis of Amino-Functionalized Hollow Mesoporous Silica for Elevated-High-Temperature Fuel Cells.

    Science.gov (United States)

    Zhang, Jin; Liu, Jian; Lu, Shanfu; Zhu, Haijin; Aili, David; De Marco, Roland; Xiang, Yan; Forsyth, Maria; Li, Qingfeng; Jiang, San Ping

    2017-09-20

    As differentiated from conventional synthetic processes, amino-functionalized hollow mesoporous silica (NH 2 -HMS) has been synthesized using a new and facile strategy of ion-exchange-induced selective etching of amino-functionalized mesoporous silica (NH 2 -meso-silica) by an alkaline solution. Nuclear magnetic resonance (NMR) spectroscopy and in situ time-resolved small-angle X-ray scattering (SAXS) reveal that ion-exchange-induced selective etching arises from the gradient distribution of OH - in the NH 2 -meso-silica nanospheres. Moreover, the ion-exchange-induced selective etching mechanism is verified through a successful synthesis of hollow mesoporous silica. After infiltration with phosphotungstic acid (PWA), PWA-NH 2 -HMS nanoparticles are dispersed in the poly(ether sulfone)-polyvinylpyrrolidone (PES-PVP) matrix, forming a hybrid PWA-NH 2 -HMS/PES-PVP nanocomposite membrane. The resultant nanocomposite membrane with an optimum loading of 10 wt % of PWA-NH 2 -HMS showed an enhanced proton conductivity of 0.175 S cm -1 and peak power density of 420 mW cm -2 at 180 °C under anhydrous conditions. Excellent durability of the hybrid composite membrane fuel cell has been demonstrated at 200 °C. The results of this study demonstrated the potential of the facile synthetic strategy in the fabrication of NH 2 -HMS with controlled mesoporous structure for application in nanocomposite membranes as a technology platform for elevated-temperature proton exchange membrane fuel cells.

  9. Optical properties of alkali halide crystals from all-electron hybrid TD-DFT calculations

    Energy Technology Data Exchange (ETDEWEB)

    Webster, R., E-mail: ross.webster07@imperial.ac.uk; Harrison, N. M. [Thomas Young Centre, Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ (United Kingdom); Bernasconi, L. [Rutherford Appleton Laboratory, STFC, Harwell Oxford, Didcot OX11 0QX (United Kingdom)

    2015-06-07

    We present a study of the electronic and optical properties of a series of alkali halide crystals AX, with A = Li, Na, K, Rb and X = F, Cl, Br based on a recent implementation of hybrid-exchange time-dependent density functional theory (TD-DFT) (TD-B3LYP) in the all-electron Gaussian basis set code CRYSTAL. We examine, in particular, the impact of basis set size and quality on the prediction of the optical gap and exciton binding energy. The formation of bound excitons by photoexcitation is observed in all the studied systems and this is shown to be correlated to specific features of the Hartree-Fock exchange component of the TD-DFT response kernel. All computed optical gaps and exciton binding energies are however markedly below estimated experimental and, where available, 2-particle Green’s function (GW-Bethe-Salpeter equation, GW-BSE) values. We attribute this reduced exciton binding to the incorrect asymptotics of the B3LYP exchange correlation ground state functional and of the TD-B3LYP response kernel, which lead to a large underestimation of the Coulomb interaction between the excited electron and hole wavefunctions. Considering LiF as an example, we correlate the asymptotic behaviour of the TD-B3LYP kernel to the fraction of Fock exchange admixed in the ground state functional c{sub HF} and show that there exists one value of c{sub HF} (∼0.32) that reproduces at least semi-quantitatively the optical gap of this material.

  10. Temperature response functions (G-functions) for single pile heat exchangers

    International Nuclear Information System (INIS)

    Loveridge, Fleur; Powrie, William

    2013-01-01

    Foundation piles used as heat exchangers as part of a ground energy system have the potential to reduce energy use and carbon dioxide emissions from new buildings. However, current design approaches for pile heat exchangers are based on methods developed for boreholes which have a different geometry, with a much larger aspect (length to diameter) ratio. Current methods also neglect the transient behaviour of the pile concrete, instead assuming a steady state resistance for design purposes. As piles have a much larger volume of concrete than boreholes, this neglects the significant potential for heat storage within the pile. To overcome these shortcomings this paper presents new pile temperature response functions (G-functions) which are designed to reflect typical geometries of pile heat exchangers and include the transient response of the pile concrete. Owing to the larger number of pile sizes and pipe configurations which are possible with pile heat exchangers it is not feasible to developed a single unified G-function and instead upper and lower bound solutions are provided for different aspects ratios. - Highlights: • We present new temperature response functions for pile heat exchangers. • The functions include transient heat transfer within the pile concrete. • Application of the functions reduces the resulting calculated temperature ranges. • Greater energy efficiency is possible by accounting for heat storage in the pile

  11. Polyploidy and the relationship between leaf structure and function: implications for correlated evolution of anatomy, morphology, and physiology in Brassica.

    Science.gov (United States)

    Baker, Robert L; Yarkhunova, Yulia; Vidal, Katherine; Ewers, Brent E; Weinig, Cynthia

    2017-01-05

    Polyploidy is well studied from a genetic and genomic perspective, but the morphological, anatomical, and physiological consequences of polyploidy remain relatively uncharacterized. Whether these potential changes bear on functional integration or are idiosyncratic remains an open question. Repeated allotetraploid events and multiple genomic combinations as well as overlapping targets of artificial selection make the Brassica triangle an excellent system for exploring variation in the connection between plant structure (anatomy and morphology) and function (physiology). We examine phenotypic integration among structural aspects of leaves including external morphology and internal anatomy with leaf-level physiology among several species of Brassica. We compare diploid and allotetraploid species to ascertain patterns of phenotypic correlations among structural and functional traits and test the hypothesis that allotetraploidy results in trait disintegration allowing for transgressive phenotypes and additional evolutionary and crop improvement potential. Among six Brassica species, we found significant effects of species and ploidy level for morphological, anatomical and physiological traits. We identified three suites of intercorrelated traits in both diploid parents and allotetraploids: Morphological traits (such as leaf area and perimeter) anatomic traits (including ab- and ad- axial epidermis) and aspects of physiology. In general, there were more correlations between structural and functional traits for allotetraploid hybrids than diploid parents. Parents and hybrids did not have any significant structure-function correlations in common. Of particular note, there were no significant correlations between morphological structure and physiological function in the diploid parents. Increased phenotypic integration in the allotetraploid hybrids may be due, in part, to increased trait ranges or simply different structure-function relationships. Genomic and chromosomal

  12. Data Exchange Protocol in Repsail

    Directory of Open Access Journals (Sweden)

    Gucma Maciej

    2017-12-01

    Full Text Available Article presents implantation and theoretical considerations of data exchange protocol developed for the RepSail project, where main objective was design and building innovative hybrid yacht. One of problems during the design process was improper functioning of data exchange protocols that were available in the commercially available devices to mention navigation purpose NMEA183 or 2000 as well as automation dedicated ones (CAN and similar. Author shows the basis of the dedicated format of exchange for in board devices.

  13. Quantum spin correction scheme based on spin-correlation functional for Kohn-Sham spin density functional theory

    International Nuclear Information System (INIS)

    Yamanaka, Shusuke; Takeda, Ryo; Nakata, Kazuto; Takada, Toshikazu; Shoji, Mitsuo; Kitagawa, Yasutaka; Yamaguchi, Kizashi

    2007-01-01

    We present a simple quantum correction scheme for ab initio Kohn-Sham spin density functional theory (KS-SDFT). This scheme is based on a mapping from ab initio results to a Heisenberg model Hamiltonian. The effective exchange integral is estimated by using energies and spin correlation functionals calculated by ab initio KS-SDFT. The quantum-corrected spin-correlation functional is open to be designed to cover specific quantum spin fluctuations. In this article, we present a simple correction for dinuclear compounds having multiple bonds. The computational results are discussed in relation to multireference (MR) DFT, by which we treat the quantum many-body effects explicitly

  14. Inflationary trispectrum from graviton exchange

    DEFF Research Database (Denmark)

    Seery, David; Sloth, Martin Snoager; Vernizzi, Filippo

    2009-01-01

    We compute the connected four-point correlation function of the primordial curvature perturbation generated during inflation with standard kinetic terms, where the correlation is established via exchange of a graviton between two pairs of scalar fluctuations. Any such correlation yields a contrib......We compute the connected four-point correlation function of the primordial curvature perturbation generated during inflation with standard kinetic terms, where the correlation is established via exchange of a graviton between two pairs of scalar fluctuations. Any such correlation yields...... where the momentum of the graviton which is exchanged becomes much smaller than the external momenta. We conclude that the total non-linearity parameter generated by single-field models of slow-roll inflation is at maximum tauNL ~ r....

  15. Cross-correlations between crude oil and exchange markets for selected oil rich economies

    Science.gov (United States)

    Li, Jianfeng; Lu, Xinsheng; Zhou, Ying

    2016-07-01

    Using multifractal detrended cross-correlation analysis (MF-DCCA), this paper studies the cross-correlation behavior between crude oil market and five selected exchange rate markets. The dataset covers the period of January 1,1996-December 31,2014, and contains 4,633 observations for each of the series, including daily closing prices of crude oil, Australian Dollars, Canadian Dollars, Mexican Pesos, Russian Rubles, and South African Rand. Our empirical results obtained from cross-correlation statistic and cross-correlation coefficient have confirmed the existence of cross-correlations, and the MF-DCCA results have demonstrated a strong multifractality between cross-correlated crude oil market and exchange rate markets in both short term and long term. Using rolling window analysis, we have also found the persistent cross-correlations between the exchange rates and crude oil returns, and the cross-correlation scaling exponents exhibit volatility during some time periods due to its sensitivity to sudden events.

  16. Theoretical investigation of pressure-induced structural transitions in americium using GGA+U and hybrid density functional theory methods

    DEFF Research Database (Denmark)

    Verma, Ashok K.; Modak, P.; Sharma, Surinder M.

    2013-01-01

    First-principles calculations have been performed for americium (Am) metal using the generalized gradient approximation + orbital-dependent onsite Coulomb repulsion via Hubbard interaction (GGA+U) and hybrid density functional theory (HYB-DFT) methods to investigate various ground state properties......-I to Am-II transition. Good agreement was found between calculated and experimental equations of states for all phases, but the first three phases need larger U (α) parameters (where α represents the fraction of Hartree-Fock exchange energy replacing the DFT exchange energy) than the fourth phase in order...

  17. Calculation of exchange coupling constants in triply-bridged dinuclear Cu(II) compounds based on spin-flip constricted variational density functional theory.

    Science.gov (United States)

    Seidu, Issaka; Zhekova, Hristina R; Seth, Michael; Ziegler, Tom

    2012-03-08

    The performance of the second-order spin-flip constricted variational density functional theory (SF-CV(2)-DFT) for the calculation of the exchange coupling constant (J) is assessed by application to a series of triply bridged Cu(II) dinuclear complexes. A comparison of the J values based on SF-CV(2)-DFT with those obtained by the broken symmetry (BS) DFT method and experiment is provided. It is demonstrated that our methodology constitutes a viable alternative to the BS-DFT method. The strong dependence of the calculated exchange coupling constants on the applied functionals is demonstrated. Both SF-CV(2)-DFT and BS-DFT affords the best agreement with experiment for hybrid functionals.

  18. Molecular excited states from the SCAN functional

    Science.gov (United States)

    Tozer, David J.; Peach, Michael J. G.

    2018-06-01

    The performance of the strongly constrained and appropriately normed (SCAN) meta-generalised gradient approximation exchange-correlation functional is investigated for the calculation of time-dependent density-functional theory molecular excitation energies of local, charge-transfer and Rydberg character, together with the excited ? potential energy curve in H2. The SCAN results frequently resemble those obtained using a global hybrid functional, with either a standard or increased fraction of exact orbital exchange. For local excitations, SCAN can exhibit significant triplet instability problems, resulting in imaginary triplet excitation energies for a number of cases. The Tamm-Dancoff approximation offers a simple approach to improve the situation, but the excitation energies are still significantly underestimated. Understanding the origin of these (near)-triplet instabilities may provide useful insight into future functional development.

  19. Evaluation of a hybrid ion exchange-catalyst treatment technology for nitrate removal from drinking water.

    Science.gov (United States)

    Bergquist, Allison M; Choe, Jong Kwon; Strathmann, Timothy J; Werth, Charles J

    2016-06-01

    Ion exchange (IX) is the most common approach to treating nitrate-contaminated drinking water sources, but the cost of salt to make regeneration brine, as well as the cost and environmental burden of waste brine disposal, are major disadvantages. A hybrid ion exchange-catalyst treatment system, in which waste brine is catalytically treated for reuse, shows promise for reducing costs and environmental burdens of the conventional IX system. An IX model with separate treatment and regeneration cycles was developed, and ion selectivity coefficients for each cycle were separately calibrated by fitting experimental data. Of note, selectivity coefficients for the regeneration cycle required fitting the second treatment cycle after incomplete resin regeneration. The calibrated and validated model was used to simulate many cycles of treatment and regeneration using the hybrid system. Simulated waste brines and a real brine obtained from a California utility were also evaluated for catalytic nitrate treatment in a packed-bed, flow-through column with 0.5 wt%Pd-0.05 wt%In/activated carbon support (PdIn/AC). Consistent nitrate removal and no apparent catalyst deactivation were observed over 23 d (synthetic brine) and 45 d (real waste brine) of continuous-flow treatment. Ion exchange and catalyst results were used to evaluate treatment of 1 billion gallons of nitrate-contaminated source water at a 0.5 MGD water treatment plant. Switching from a conventional IX system with a two bed volume regeneration to a hybrid system with the same regeneration length and sequencing batch catalytic reactor treatment would save 76% in salt cost. The results suggest the hybrid system has the potential to address the disadvantages of a conventional IX treatment systems. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Teager Correlation Function

    DEFF Research Database (Denmark)

    Bysted, Tommy Kristensen; Hamila, R.; Gabbouj, M.

    1998-01-01

    A new correlation function called the Teager correlation function is introduced in this paper. The connection between this function, the Teager energy operator and the conventional correlation function is established. Two applications are presented. The first is the minimization of the Teager error...... norm and the second one is the use of the instantaneous Teager correlation function for simultaneous estimation of TDOA and FDOA (Time and Frequency Difference of Arrivals)....

  1. Directly patching high-level exchange-correlation potential based on fully determined optimized effective potentials

    Science.gov (United States)

    Huang, Chen; Chi, Yu-Chieh

    2017-12-01

    The key element in Kohn-Sham (KS) density functional theory is the exchange-correlation (XC) potential. We recently proposed the exchange-correlation potential patching (XCPP) method with the aim of directly constructing high-level XC potential in a large system by patching the locally computed, high-level XC potentials throughout the system. In this work, we investigate the patching of the exact exchange (EXX) and the random phase approximation (RPA) correlation potentials. A major challenge of XCPP is that a cluster's XC potential, obtained by solving the optimized effective potential equation, is only determined up to an unknown constant. Without fully determining the clusters' XC potentials, the patched system's XC potential is "uneven" in the real space and may cause non-physical results. Here, we developed a simple method to determine this unknown constant. The performance of XCPP-RPA is investigated on three one-dimensional systems: H20, H10Li8, and the stretching of the H19-H bond. We investigated two definitions of EXX: (i) the definition based on the adiabatic connection and fluctuation dissipation theorem (ACFDT) and (ii) the Hartree-Fock (HF) definition. With ACFDT-type EXX, effective error cancellations were observed between the patched EXX and the patched RPA correlation potentials. Such error cancellations were absent for the HF-type EXX, which was attributed to the fact that for systems with fractional occupation numbers, the integral of the HF-type EXX hole is not -1. The KS spectra and band gaps from XCPP agree reasonably well with the benchmarks as we make the clusters large.

  2. Effects of wave function correlations on scaling violation in quasi-free electron scattering

    International Nuclear Information System (INIS)

    Tornow, V.; Drechsel, D.; Orlandini, G.; Traini, M.

    1981-01-01

    The scaling law in quasi-free electron scattering is broken due to the existence of exchange forces, leading to a finite mean value of the scaling variable anti y. This effect is considerably increased by wave function correlations, in particular by tensor correlations, similar to the case of the photonuclear enhancement factor k. (orig.)

  3. Numerical Study of Condensation Heat Exchanger Design in a Subcooled Pool: Correlation Investigation

    International Nuclear Information System (INIS)

    Lee, Hee Joon; Ju, Yun Jae; Kang, Han Ok; Lee, Tae Ho; Park, Cheon Tae

    2012-01-01

    Generally the condensation heat exchanger has higher heat transfer coefficient compared to the single phase heat exchanger, so has been widely applied to the cooling systems of energy plant. Recently vertical or horizontal type condensation heat exchangers are being studied for the application to secondary passive cooling system of nuclear plants. Lee and Lee investigated the existing condensation correlation to the experiment for heat exchanger in saturated pool. They concluded Traviss' correlation showed most satisfactory results for the heat transfer coefficient and mass flow rate in a saturated water pool. In this study, a thermal sizing program of vertical condensation heat exchanger to design, TSCON(Thermal Sizing of CONdenser) was validated with the existing experimental data of condensation heat exchanger in a subcooled pool for pure steam condensation

  4. Currency co-movement and network correlation structure of foreign exchange market

    Science.gov (United States)

    Mai, Yong; Chen, Huan; Zou, Jun-Zhong; Li, Sai-Ping

    2018-02-01

    We study the correlations of exchange rate volatility in the global foreign exchange(FX) market based on complex network graphs. Correlation matrices (CM) and the theoretical information flow method (Infomap) are employed to analyze the modular structure of the global foreign exchange network. The analysis demonstrates that there exist currency modules in the network, which is consistent with the geographical nature of currencies. The European and the East Asian currency modules in the FX network are most significant. We introduce a measure of the impact of individual currency based on its partial correlations with other currencies. We further incorporate an impact elimination method to filter out the impact of core nodes and construct subnetworks after the removal of these core nodes. The result reveals that (i) the US Dollar has prominent global influence on the FX market while the Euro has great impact on European currencies; (ii) the East Asian currency module is more strongly correlated than the European currency module. The strong correlation is a result of the strong co-movement of currencies in the region. The co-movement of currencies is further used to study the formation of international monetary bloc and the result is in good agreement with the consideration based on international trade.

  5. Synthesis and characterizations of anion exchange organic-inorganic hybrid materials based on poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)

    International Nuclear Information System (INIS)

    Zhang Shaoling; Wu Cuiming; Xu Tongwen; Gong Ming; Xu Xiaolong

    2005-01-01

    A series of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)-based organic-inorganic hybrid materials for anion exchange were prepared through sol-gel process of polymer precursors PPO-Si(OCH 3 ) 3 . PPO-Si(OCH 3 ) 3 were obtained from the reaction of bromomethylated PPO with 3-aminopropyl-trimethoxysilane (A1110). These polymer precursors then underwent hydrolysis and condensation with additional A1110 to generate hybrid materials. The reaction to produce polymer precursors was identified by FTIR; while FTIR, TGA, XRD, SEM, as well as conventional ion exchange capacity (IEC) measurements were conducted for the structures and properties of the prepared hybrids. TGA results show that this series of hybrid materials possess high thermal stability; XRD and SEM indicate that the prepared hybrid materials are amorphous and the inorganic and organic contents show good compatibility if the ratio between them is proper. The IEC values of the hybrid materials due to the amine groups range from 1.13 mmol/gBPPO (material i) to 4.80 mmol/gBPPO (material iv)

  6. Correlation between charge transfer and exchange coupling in carbon-based magnetic materials

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Anh Tuan, E-mail: tuanna@hus.edu.vn [Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Ha Noi (Viet Nam); Science and Technology Department, Vietnam National University, Hanoi, 144 Xuan Thuy, Cau Giay, Hanoi (Viet Nam); Japan Advanced Institute of Science and Technology, 1-1, Asahidai, Nomi, Ishikawa, 923-1292 Japan (Japan); Nguyen, Van Thanh; Nguyen, Huy Sinh [Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Ha Noi (Viet Nam); Pham, Thi Tuan Anh [Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Ha Noi (Viet Nam); Faculty of Science, College of Hai Duong, Nguyen Thi Due, Hai Duong (Viet Nam); Do, Viet Thang [Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Ha Noi (Viet Nam); Faculty of Science, Haiphong University, 171 Phan Dang Luu, Kien An, Hai Phong (Viet Nam); Dam, Hieu Chi [Japan Advanced Institute of Science and Technology, 1-1, Asahidai, Nomi, Ishikawa, 923-1292 Japan (Japan)

    2015-10-15

    Several forms of carbon-based magnetic materials, i.e. single radicals, radical dimers, and alternating stacks of radicals and diamagnetic molecules, have been investigated using density-functional theory with dispersion correction and full geometry optimization. Our calculated results demonstrate that the C{sub 31}H{sub 15} (R{sub 4}) radical has a spin of ½. However, in its [R{sub 4}]{sub 2} dimer structure, the net spin becomes zero due to antiferromagnetic spin-exchange between radicals. To avoid antiferromagnetic spin-exchange of identical face-to-face radicals, eight alternating stacks, R{sub 4}/D{sub 2m}/R{sub 4} (with m = 3-10), were designed. Our calculated results show that charge transfer (Δn) between R{sub 4} radicals and the diamagnetic molecule D{sub 2m} occurs with a mechanism of spin exchange (J) in stacks. The more electrons that transfer from R{sub 4} to D{sub 2m}, the stronger the ferromagnetic spin-exchange in stacks. In addition, our calculated results show that Δn can be tailored by adjusting the electron affinity (E{sub a}) of D{sub 2m}. The correlation between Δn, E{sub a}, m, and J is discussed. These results give some hints for the design of new ferromagnetic carbon-based materials.

  7. High ion-exchange properties of hybrid materials from X-type zeolite and ground glass powder

    Science.gov (United States)

    Taira, Nobuyuki; Yoshida, Kohei

    2017-10-01

    Zeolites are crystalline aluminosilicates with a homogeneous distribution of micropores with a superior cation-exchange capacity. Because they have especially excellent selective exchange properties, a considerable number of studies have been conducted on treating water containing radioisotopes using the zeolites. When using artificial zeolites, they have inferior sinterability; in addition, it is quite hard for them to remove from polluted liquid since these artificial zeolites are principally synthesized as a form of powder, which is a disadvantage. In this study, hybrid materials were prepared from X-type zeolite and waste glass powder. Their ion-removal effect and mechanical strength were investigated. The zeolite and waste glass were ground in an agate mortar in several ratios. 0.5 g of the mixture was pressure-molded into pellets having a diameter of 7 mm. These pellets were slowly heated at the speed of 240°C/h to 700°C and maintained at 700°C for 2 h. The removal rate of Sr2+ ions increased as the amount of X-type zeolite in the hybrid materials increased; the former increased up to 100% when the content of latter exceeded 50%. The mechanical strength increased by increasing the amount of glass in the hybrid materials. This is attributed to the fact that the glass powder acts as a binder that improves the densification and consequently the mechanical strength of the hybrid materials.

  8. Hybrid systems with lead-acid battery and proton-exchange membrane fuel cell

    Science.gov (United States)

    Jossen, Andreas; Garche, Juergen; Doering, Harry; Goetz, Markus; Knaupp, Werner; Joerissen, Ludwig

    Hybrid systems, based on a lead-acid battery and a proton-exchange membrane fuel cell (PEMFC) give the possibility to combine the advantages of both technologies. The benefits for different applications are discussed and the practical realisation of such systems is shown. Furthermore a numerical model for such a hybrid system is described and results are shown and discussed. The results show that the combination of lead-acid batteries and PEMFC shows advantages in case of applications with high peak power requirements (i.e. electric scooter) and applications where the fuel cell is used as auxiliary power supply to recharge the battery. The high efficiency of fuel cells at partial load operation results in a good fuel economy for recharging of lead-acid batteries with a fuel cell system.

  9. Analyzing the Cross-Correlation Between Onshore and Offshore RMB Exchange Rates Based on Multifractal Detrended Cross-Correlation Analysis (MF-DCCA)

    Science.gov (United States)

    Xie, Chi; Zhou, Yingying; Wang, Gangjin; Yan, Xinguo

    We use the multifractal detrended cross-correlation analysis (MF-DCCA) method to explore the multifractal behavior of the cross-correlation between exchange rates of onshore RMB (CNY) and offshore RMB (CNH) against US dollar (USD). The empirical data are daily prices of CNY/USD and CNH/USD from May 1, 2012 to February 29, 2016. The results demonstrate that: (i) the cross-correlation between CNY/USD and CNH/USD is persistent and its fluctuation is smaller when the order of fluctuation function is negative than that when the order is positive; (ii) the multifractal behavior of the cross-correlation between CNY/USD and CNH/USD is significant during the sample period; (iii) the dynamic Hurst exponents obtained by the rolling windows analysis show that the cross-correlation is stable when the global economic situation is good and volatile in bad situation; and (iv) the non-normal distribution of original data has a greater effect on the multifractality of the cross-correlation between CNY/USD and CNH/USD than the temporary correlation.

  10. A new quantum statistical evaluation method for time correlation functions

    International Nuclear Information System (INIS)

    Loss, D.; Schoeller, H.

    1989-01-01

    Considering a system of N identical interacting particles, which obey Fermi-Dirac or Bose-Einstein statistics, the authors derive new formulas for correlation functions of the type C(t) = i= 1 N A i (t) Σ j=1 N B j > (where B j is diagonal in the free-particle states) in the thermodynamic limit. Thereby they apply and extend a superoperator formalism, recently developed for the derivation of long-time tails in semiclassical systems. As an illustrative application, the Boltzmann equation value of the time-integrated correlation function C(t) is derived in a straight-forward manner. Due to exchange effects, the obtained t-matrix and the resulting scattering cross section, which occurs in the Boltzmann collision operator, are now functionals of the Fermi-Dirac or Bose-Einstein distribution

  11. Influence of super-horizon modes on correlation functions during inflation

    Science.gov (United States)

    Deutsch, Anne-Sylvie

    2018-05-01

    Coupling between sub- and super-Hubble modes can affect the locally observed statistics of our universe. In the context of Quasi-Single Field Inflation, we can compute correlation functions and derive the influence of those unobservable modes on observed correlation functions as well as on the inferred cosmological parameters. We study how different classes of diagrams affect the bispectrum in the squeezed limit; in particular, while contact-like diagrams leave the scaling between the long and short modes unchanged, exchange-like diagrams do modify the shape of the bispectrum. We show that the mass of the hidden sector field can hence be biased by an unavoidable cosmic variance that can reach a 1-σ uncertainty of Script O(10%) for a weakly non-Gaussian universe. Finally, we go beyond the bispectrum and show how couplings between unobservable and observable modes can affect generic correlation functions with arbitrary order non-derivative self-interactions.

  12. Maximally localized Wannier functions in LaMnO3 within PBE + U, hybrid functionals and partially self-consistent GW: an efficient route to construct ab initio tight-binding parameters for eg perovskites.

    Science.gov (United States)

    Franchini, C; Kováčik, R; Marsman, M; Murthy, S Sathyanarayana; He, J; Ederer, C; Kresse, G

    2012-06-13

    Using the newly developed VASP2WANNIER90 interface we have constructed maximally localized Wannier functions (MLWFs) for the e(g) states of the prototypical Jahn-Teller magnetic perovskite LaMnO(3) at different levels of approximation for the exchange-correlation kernel. These include conventional density functional theory (DFT) with and without the additional on-site Hubbard U term, hybrid DFT and partially self-consistent GW. By suitably mapping the MLWFs onto an effective e(g) tight-binding (TB) Hamiltonian we have computed a complete set of TB parameters which should serve as guidance for more elaborate treatments of correlation effects in effective Hamiltonian-based approaches. The method-dependent changes of the calculated TB parameters and their interplay with the electron-electron (el-el) interaction term are discussed and interpreted. We discuss two alternative model parameterizations: one in which the effects of the el-el interaction are implicitly incorporated in the otherwise 'noninteracting' TB parameters and a second where we include an explicit mean-field el-el interaction term in the TB Hamiltonian. Both models yield a set of tabulated TB parameters which provide the band dispersion in excellent agreement with the underlying ab initio and MLWF bands.

  13. Hybrid ion-exchange membranes for fuel cells and separation processes

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Carretero, F.J.; Compan, V. [Departamento de Termodinamica Aplicada, ETSII, Universidad Politecnica de Valencia, 46020 Valencia (Spain); Riande, E. [Instituto de Ciencia y Tecnologia de Polimeros (CSIC), 28006 Madrid (Spain)

    2007-11-08

    This work reports the preparation and characterization of hybrid membranes cast from dispersions of inorganic fillers in sulfonated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene solutions. Silica gel, SBA-15 and sepiolite, all of them functionalized with phenylsulfonic acid groups, were used as fillers. For comparative purposes, the performance of composite membranes cast from dispersions of functionalized inorganic fillers in Nafion {sup registered} solutions was investigated. Inspection of the texture of the membranes by using SEM techniques shows that the fillers are better dispersed in sulfonated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene than in Nafion {sup registered}. The value of the water uptake for the membranes prepared from the former polyelectrolyte is in most cases at least three times that measured for hybrid Nafion {sup registered} membranes. The conductivity of the membranes was measured at 80 C by impedance spectroscopy obtaining values of 3.44, 6.90 and 3.54 S m{sup -1} for the hybrid membranes based on the triblock copolymer containing functionalized silica gel, SBA-15 and sepiolite fillers, respectively. These results compare very favourably with those obtained at 80 C for Nafion {sup registered} hybrid membranes containing silica gel, SBA-15 and sepiolite, all of them fuctionalized with phenylsulfonic acid groups, whose conductivities are, 2.84, 6.75 and 3.31 S m{sup -1}, respectively. Resistance measurements carried out under controlled humidity conditions show that the conductivity of sulfonated triblock copolymer membranes containing functionalized SBA-15 filler undergoes a rather sharp increase when they are conditioned under an atmosphere of 75%, or larger, relative humidity. (author)

  14. Exchange-correlation energy from pairing matrix fluctuation and the particle-particle random phase approximation.

    Science.gov (United States)

    van Aggelen, Helen; Yang, Yang; Yang, Weitao

    2014-05-14

    Despite their unmatched success for many applications, commonly used local, semi-local, and hybrid density functionals still face challenges when it comes to describing long-range interactions, static correlation, and electron delocalization. Density functionals of both the occupied and virtual orbitals are able to address these problems. The particle-hole (ph-) Random Phase Approximation (RPA), a functional of occupied and virtual orbitals, has recently known a revival within the density functional theory community. Following up on an idea introduced in our recent communication [H. van Aggelen, Y. Yang, and W. Yang, Phys. Rev. A 88, 030501 (2013)], we formulate more general adiabatic connections for the correlation energy in terms of pairing matrix fluctuations described by the particle-particle (pp-) propagator. With numerical examples of the pp-RPA, the lowest-order approximation to the pp-propagator, we illustrate the potential of density functional approximations based on pairing matrix fluctuations. The pp-RPA is size-extensive, self-interaction free, fully anti-symmetric, describes the strong static correlation limit in H2, and eliminates delocalization errors in H2(+) and other single-bond systems. It gives surprisingly good non-bonded interaction energies--competitive with the ph-RPA--with the correct R(-6) asymptotic decay as a function of the separation R, which we argue is mainly attributable to its correct second-order energy term. While the pp-RPA tends to underestimate absolute correlation energies, it gives good relative energies: much better atomization energies than the ph-RPA, as it has no tendency to underbind, and reaction energies of similar quality. The adiabatic connection in terms of pairing matrix fluctuation paves the way for promising new density functional approximations.

  15. Exchange-correlation energy from pairing matrix fluctuation and the particle-particle random phase approximation

    International Nuclear Information System (INIS)

    Aggelen, Helen van; Yang, Yang; Yang, Weitao

    2014-01-01

    Despite their unmatched success for many applications, commonly used local, semi-local, and hybrid density functionals still face challenges when it comes to describing long-range interactions, static correlation, and electron delocalization. Density functionals of both the occupied and virtual orbitals are able to address these problems. The particle-hole (ph-) Random Phase Approximation (RPA), a functional of occupied and virtual orbitals, has recently known a revival within the density functional theory community. Following up on an idea introduced in our recent communication [H. van Aggelen, Y. Yang, and W. Yang, Phys. Rev. A 88, 030501 (2013)], we formulate more general adiabatic connections for the correlation energy in terms of pairing matrix fluctuations described by the particle-particle (pp-) propagator. With numerical examples of the pp-RPA, the lowest-order approximation to the pp-propagator, we illustrate the potential of density functional approximations based on pairing matrix fluctuations. The pp-RPA is size-extensive, self-interaction free, fully anti-symmetric, describes the strong static correlation limit in H 2 , and eliminates delocalization errors in H 2 + and other single-bond systems. It gives surprisingly good non-bonded interaction energies – competitive with the ph-RPA – with the correct R −6 asymptotic decay as a function of the separation R, which we argue is mainly attributable to its correct second-order energy term. While the pp-RPA tends to underestimate absolute correlation energies, it gives good relative energies: much better atomization energies than the ph-RPA, as it has no tendency to underbind, and reaction energies of similar quality. The adiabatic connection in terms of pairing matrix fluctuation paves the way for promising new density functional approximations

  16. Increasing the applicability of density functional theory. V. X-ray absorption spectra with ionization potential corrected exchange and correlation potentials

    Energy Technology Data Exchange (ETDEWEB)

    Verma, Prakash; Bartlett, Rodney J., E-mail: bartlett@qtp.ufl.edu [Quantum Theory Project, University of Florida, Gainesville, Florida 32611 (United States)

    2016-07-21

    Core excitation energies are computed with time-dependent density functional theory (TD-DFT) using the ionization energy corrected exchange and correlation potential QTP(0,0). QTP(0,0) provides C, N, and O K-edge spectra to about an electron volt. A mean absolute error (MAE) of 0.77 and a maximum error of 2.6 eV is observed for QTP(0,0) for many small molecules. TD-DFT based on QTP (0,0) is then used to describe the core-excitation spectra of the 22 amino acids. TD-DFT with conventional functionals greatly underestimates core excitation energies, largely due to the significant error in the Kohn-Sham occupied eigenvalues. To the contrary, the ionization energy corrected potential, QTP(0,0), provides excellent approximations (MAE of 0.53 eV) for core ionization energies as eigenvalues of the Kohn-Sham equations. As a consequence, core excitation energies are accurately described with QTP(0,0), as are the core ionization energies important in X-ray photoionization spectra or electron spectroscopy for chemical analysis.

  17. Increasing the applicability of density functional theory. V. X-ray absorption spectra with ionization potential corrected exchange and correlation potentials.

    Science.gov (United States)

    Verma, Prakash; Bartlett, Rodney J

    2016-07-21

    Core excitation energies are computed with time-dependent density functional theory (TD-DFT) using the ionization energy corrected exchange and correlation potential QTP(0,0). QTP(0,0) provides C, N, and O K-edge spectra to about an electron volt. A mean absolute error (MAE) of 0.77 and a maximum error of 2.6 eV is observed for QTP(0,0) for many small molecules. TD-DFT based on QTP (0,0) is then used to describe the core-excitation spectra of the 22 amino acids. TD-DFT with conventional functionals greatly underestimates core excitation energies, largely due to the significant error in the Kohn-Sham occupied eigenvalues. To the contrary, the ionization energy corrected potential, QTP(0,0), provides excellent approximations (MAE of 0.53 eV) for core ionization energies as eigenvalues of the Kohn-Sham equations. As a consequence, core excitation energies are accurately described with QTP(0,0), as are the core ionization energies important in X-ray photoionization spectra or electron spectroscopy for chemical analysis.

  18. Exchange and spin-fluctuation superconducting pairing in the strong correlation limit of the Hubbard model

    International Nuclear Information System (INIS)

    Plakida, N. M.; Anton, L.; Adam, S. . Department of Theoretical Physics, Horia Hulubei National Institute for Physics and Nuclear Engineering, PO Box MG-6, RO-76900 Bucharest - Magurele; RO); Adam, Gh. . Department of Theoretical Physics, Horia Hulubei National Institute for Physics and Nuclear Engineering, PO Box MG-6, RO-76900 Bucharest - Magurele; RO)

    2001-01-01

    A microscopical theory of superconductivity in the two-band singlet-hole Hubbard model, in the strong coupling limit in a paramagnetic state, is developed. The model Hamiltonian is obtained by projecting the p-d model to an asymmetric Hubbard model with the lower Hubbard subband occupied by one-hole Cu d-like states and the upper Hubbard subband occupied by two-hole p-d singlet states. The model requires two microscopical parameters only, the p-d hybridization parameter t and the charge-transfer gap Δ. It was previously shown to secure an appropriate description of the normal state properties of the high -T c cuprates. To treat rigorously the strong correlations, the Hubbard operator technique within the projection method for the Green function is used. The Dyson equation is derived. In the molecular field approximation, d-wave superconducting pairing of conventional hole (electron) pairs in one Hubbard subband is found, which is mediated by the exchange interaction given by the interband hopping, J ij = 4 (t ij ) 2 / Δ. The normal and anomalous components of the self-energy matrix are calculated in the self-consistent Born approximation for the electron-spin-fluctuation scattering mediated by kinematic interaction of the second order of the intraband hopping. The derived numerical and analytical solutions predict the occurrence of singlet d x 2 -y 2 -wave pairing both in the d-hole and singlet Hubbard subbands. The gap functions and T c are calculated for different hole concentrations. The exchange interaction is shown to be the most important pairing interaction in the Hubbard model in the strong correlation limit, while the spin-fluctuation coupling results only in a moderate enhancement of T c . The smaller weight of the latter comes from two specific features: its vanishing inside the Brillouin zone (BZ) along the lines, |k x | + |k y |=π pointing towards the hot spots and the existence of a small energy shell within which the pairing is effective. By

  19. A multiconfigurational hybrid density-functional theory

    DEFF Research Database (Denmark)

    Sharkas, Kamal; Savin, Andreas; Jensen, Hans Jørgen Aagaard

    2012-01-01

    We propose a multiconfigurational hybrid density-functional theory which rigorously combines a multiconfiguration self-consistent-field calculation with a density-functional approximation based on a linear decomposition of the electron-electron interaction. This gives a straightforward extension ...

  20. Investigation of Condensation Heat Transfer Correlation of Heat Exchanger Design in Secondary Passive Cooling System

    Energy Technology Data Exchange (ETDEWEB)

    Ju, Yun Jae; Lee, Hee Joon [Kookmin Univ., Seoul (Korea, Republic of); Kang, Hanok; Lee, Taeho; Park, Cheontae [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2013-12-15

    Recently, condensation heat exchangers have been studied for applications to the passive cooling systems of nuclear plants. To design vertical-type condensation heat exchangers in secondary passive cooling systems, TSCON (Thermal Sizing of CONdenser), a thermal sizing program for a condensation heat exchanger, was developed at KAERI (Korea Atomic Energy Research Institute). In this study, the existing condensation heat transfer correlation of TSCON was evaluated using 1,157 collected experimental data points from the heat exchanger of a secondary passive cooling system for the case of pure steam condensation. The investigation showed that the Shah correlation, published in 2009, provided the most satisfactory results for the heat transfer coefficient with a mean absolute error of 34.8%. It is suggested that the Shah correlation is appropriate for designing a condensation heat exchanger in TSCON.

  1. Parallel Implementation of Gamma-Point Pseudopotential Plane-Wave DFT with Exact Exchange

    International Nuclear Information System (INIS)

    Bylaska, Eric J.; Tsemekhman, Kiril L.; Baden, Scott B.; Weare, John H.; Jonsson, Hannes

    2011-01-01

    One of the more persistent failures of conventional density functional theory (DFT) methods has been their failure to yield localized charge states such as polarons, excitons and solitons in solid-state and extended systems. It has been suggested that conventional DFT functionals, which are not self-interaction free, tend to favor delocalized electronic states since self-interaction creates a Coulomb barrier to charge localization. Pragmatic approaches in which the exchange correlation functionals are augmented with small amount of exact exchange (hybrid-DFT, e.g. B3LYP and PBE0) have shown promise in localizing charge states and predicting accurate band gaps and reaction barriers. We have developed a parallel algorithm for implementing exact exchange into pseudopotential plane-wave density functional theory and we have implemented it in the NWChem program package. The technique developed can readily be employed in plane-wave DFT programs. Furthermore, atomic forces and stresses are straightforward to implement, making it applicable to both confined and extended systems, as well as to Car-Parrinello ab initio molecular dynamic simulations. This method has been applied to several systems for which conventional DFT methods do not work well, including calculations for band gaps in oxides and the electronic structure of a charge trapped state in the Fe(II) containing mica, annite.

  2. World currency exchange rate cross-correlations

    Science.gov (United States)

    Droå¼dż, S.; Górski, A. Z.; Kwapień, J.

    2007-08-01

    World currency network constitutes one of the most complex structures that is associated with the contemporary civilization. On a way towards quantifying its characteristics we study the cross correlations in changes of the daily foreign exchange rates within the basket of 60 currencies in the period December 1998 May 2005. Such a dynamics turns out to predominantly involve one outstanding eigenvalue of the correlation matrix. The magnitude of this eigenvalue depends however crucially on which currency is used as a base currency for the remaining ones. Most prominent it looks from the perspective of a peripheral currency. This largest eigenvalue is seen to systematically decrease and thus the structure of correlations becomes more heterogeneous, when more significant currencies are used as reference. An extreme case in this later respect is the USD in the period considered. Besides providing further insight into subtle nature of complexity, these observations point to a formal procedure that in general can be used for practical purposes of measuring the relative currencies significance on various time horizons.

  3. A New Hybrid Proton-Exchange-Membrane Fuel Cells-Battery Power System with Efficiencies Considered

    Science.gov (United States)

    Chao, Chung-Hsing; Shieh, Jenn-Jong

    Hybrid systems, based on lead-acid or lithium-ion batteries and proton-exchange-membrane fuel cells (PEMFCs), give the possibility of combining the benefit of both technologies. The merits of high energy density and power density for different applications are discussed in this paper in recognition of the practical realization of such hybrid power systems. Furthermore, experimental data for such a hybrid system is described and the results are shown and discussed. The results show that the combination of lead-acid batteries or lithium-ion batteries and PEMFCs shows advantages in cases of applications with high peak power requirements, such as electric scooters and applications where the fuel cell (FC) is used as an auxiliary power-supply to recharge the battery. The high efficiency of FCs operating with a partial load results in a good fuel economy for the purpose of recharging batteries within a FC system.

  4. Optimizations of spin-exchange relaxation-free magnetometer based on potassium and rubidium hybrid optical pumping

    International Nuclear Information System (INIS)

    Fang, Jiancheng; Wang, Tao; Li, Yang; Zhang, Hong; Zou, Sheng

    2014-01-01

    The hybrid optical pumping atomic magnetometers have not realized its theoretical sensitivity, the optimization is critical for optimal performance. The optimizations proposed in this paper are suitable for hybrid optical pumping atomic magnetometer, which contains two alkali species. To optimize the parameters, the dynamic equations of spin evolution with two alkali species were solved, whose steady-state solution is used to optimize the parameters. The demand of the power of the pump beam is large for hybrid optical pumping. Moreover, the sensitivity of the hybrid optical pumping magnetometer increases with the increase of the power density of the pump beam. The density ratio between the two alkali species is especially important for hybrid optical pumping magnetometer. A simple expression for optimizing the density ratio is proposed in this paper, which can help to determine the mole faction of the alkali atoms in fabricating the hybrid cell before the cell is sealed. The spin-exchange rate between the two alkali species is proportional to the saturated density of the alkali vapor, which is highly dependent on the temperature of the cell. Consequently, the sensitivity of the hybrid optical pumping magnetometer is dependent on the temperature of the cell. We proposed the thermal optimization of the hybrid cell for a hybrid optical pumping magnetometer, which can improve the sensitivity especially when the power of the pump beam is low. With these optimizations, a sensitivity of approximately 5 fT/Hz 1/2 is achieved with gradiometer arrangement

  5. The X3LYP extended density functional for accurate descriptions of nonbond interactions, spin states, and thermochemical properties

    Science.gov (United States)

    Xu, Xin; Goddard, William A.

    2004-01-01

    We derive the form for an exact exchange energy density for a density decaying with Gaussian-like behavior at long range. Based on this, we develop the X3LYP (extended hybrid functional combined with Lee–Yang–Parr correlation functional) extended functional for density functional theory to significantly improve the accuracy for hydrogen-bonded and van der Waals complexes while also improving the accuracy in heats of formation, ionization potentials, electron affinities, and total atomic energies [over the most popular and accurate method, B3LYP (Becke three-parameter hybrid functional combined with Lee–Yang–Parr correlation functional)]. X3LYP also leads to a good description of dipole moments, polarizabilities, and accurate excitation energies from s to d orbitals for transition metal atoms and ions. We suggest that X3LYP will be useful for predicting ligand binding in proteins and DNA. PMID:14981235

  6. From The Cover: The X3LYP extended density functional for accurate descriptions of nonbond interactions, spin states, and thermochemical properties

    Science.gov (United States)

    Xu, Xin; Goddard, William A., III

    2004-03-01

    We derive the form for an exact exchange energy density for a density decaying with Gaussian-like behavior at long range. Based on this, we develop the X3LYP (extended hybrid functional combined with Lee-Yang-Parr correlation functional) extended functional for density functional theory to significantly improve the accuracy for hydrogen-bonded and van der Waals complexes while also improving the accuracy in heats of formation, ionization potentials, electron affinities, and total atomic energies [over the most popular and accurate method, B3LYP (Becke three-parameter hybrid functional combined with Lee-Yang-Parr correlation functional)]. X3LYP also leads to a good description of dipole moments, polarizabilities, and accurate excitation energies from s to d orbitals for transition metal atoms and ions. We suggest that X3LYP will be useful for predicting ligand binding in proteins and DNA.

  7. Quantifying NMR relaxation correlation and exchange in articular cartilage with time domain analysis

    Science.gov (United States)

    Mailhiot, Sarah E.; Zong, Fangrong; Maneval, James E.; June, Ronald K.; Galvosas, Petrik; Seymour, Joseph D.

    2018-02-01

    Measured nuclear magnetic resonance (NMR) transverse relaxation data in articular cartilage has been shown to be multi-exponential and correlated to the health of the tissue. The observed relaxation rates are dependent on experimental parameters such as solvent, data acquisition methods, data analysis methods, and alignment to the magnetic field. In this study, we show that diffusive exchange occurs in porcine articular cartilage and impacts the observed relaxation rates in T1-T2 correlation experiments. By using time domain analysis of T2-T2 exchange spectroscopy, the diffusive exchange time can be quantified by measurements that use a single mixing time. Measured characteristic times for exchange are commensurate with T1 in this material and so impacts the observed T1 behavior. The approach used here allows for reliable quantification of NMR relaxation behavior in cartilage in the presence of diffusive fluid exchange between two environments.

  8. Correlated binomial models and correlation structures

    International Nuclear Information System (INIS)

    Hisakado, Masato; Kitsukawa, Kenji; Mori, Shintaro

    2006-01-01

    We discuss a general method to construct correlated binomial distributions by imposing several consistent relations on the joint probability function. We obtain self-consistency relations for the conditional correlations and conditional probabilities. The beta-binomial distribution is derived by a strong symmetric assumption on the conditional correlations. Our derivation clarifies the 'correlation' structure of the beta-binomial distribution. It is also possible to study the correlation structures of other probability distributions of exchangeable (homogeneous) correlated Bernoulli random variables. We study some distribution functions and discuss their behaviours in terms of their correlation structures

  9. Prediction of the equilibrium structures and photomagnetic properties of the Prussian blue analogue RbMn[Fe(CN)(6)] by density functional theory

    NARCIS (Netherlands)

    Luzon, Javier; Castro, Miguel; Vertelman, Esther J.M.; Gengler, Régis Y.N.; van Koningsbruggen, Petra J.; Molodtsova, Olga; Knupfer, Martin; Rudolf, Petra; Loosdrecht, Paul H.M. van; Broer, Ria

    2008-01-01

    A periodic density functional theory method using the B3LYP hybrid exchange-correlation potential is applied to the Prussian blue analogue RbMn[Fe(CN)(6)] to evaluate the suitability of the method for studying, and predicting, the photomagnetic behavior of Prussian blue analogues and related

  10. Hybrid nanostructures: synthesis, morphology and functional properties

    International Nuclear Information System (INIS)

    Povolotskaya, A V; Povolotskiy, A V; Manshina, A A

    2015-01-01

    Hybrid nanostructures representing combinations of different materials and possessing properties that are absent in separate components forming the hybrid are discussed. Particular attention is given to hybrid structures containing plasmonic and magnetic nanoparticles, methods of their synthesis and the relationship between the composition, structure and properties. The functional features of the hybrid nanomaterials of various morphology (with core–shell structures, with encapsulated metal nanoparticles and with metal nanoparticles on the surface) are considered. The unique properties of these hybrid materials are demonstrated, which are of interest for solving problems of catalysis and photocatalysis, detecting impurities in various media, in vivo visualization, bioanalysis, as well as for the design of optical labels and multifunctional diagnostic nanoplatforms. The bibliography includes 182 references

  11. Electron-hydrogen atom inelastic scattering through a correlated wave function

    International Nuclear Information System (INIS)

    Serpa Vieira, A.E. de.

    1984-01-01

    The inelastic collision between an electron and a hydrogen atom is studied. A correlated function, used previously to the same system in elastic collisions in which there are two parameters fitted in the energy range studied, is utilized. With this functions an equation is developed for the direct and exchange transition matrix elements to the 15-25 and 15-2 p transitions. The obtained results are compared with Willians experimental measurements, as well the results given by the theoretical treatments of Kingston, Fon and Burke. (L.C.) [pt

  12. Universal Spatial Correlation Functions for Describing and Reconstructing Soil Microstructure

    Science.gov (United States)

    Skvortsova, Elena B.; Mallants, Dirk

    2015-01-01

    Structural features of porous materials such as soil define the majority of its physical properties, including water infiltration and redistribution, multi-phase flow (e.g. simultaneous water/air flow, or gas exchange between biologically active soil root zone and atmosphere) and solute transport. To characterize soil microstructure, conventional soil science uses such metrics as pore size and pore-size distributions and thin section-derived morphological indicators. However, these descriptors provide only limited amount of information about the complex arrangement of soil structure and have limited capability to reconstruct structural features or predict physical properties. We introduce three different spatial correlation functions as a comprehensive tool to characterize soil microstructure: 1) two-point probability functions, 2) linear functions, and 3) two-point cluster functions. This novel approach was tested on thin-sections (2.21×2.21 cm2) representing eight soils with different pore space configurations. The two-point probability and linear correlation functions were subsequently used as a part of simulated annealing optimization procedures to reconstruct soil structure. Comparison of original and reconstructed images was based on morphological characteristics, cluster correlation functions, total number of pores and pore-size distribution. Results showed excellent agreement for soils with isolated pores, but relatively poor correspondence for soils exhibiting dual-porosity features (i.e. superposition of pores and micro-cracks). Insufficient information content in the correlation function sets used for reconstruction may have contributed to the observed discrepancies. Improved reconstructions may be obtained by adding cluster and other correlation functions into reconstruction sets. Correlation functions and the associated stochastic reconstruction algorithms introduced here are universally applicable in soil science, such as for soil classification

  13. Investigation of iron spin crossover pressure in Fe-bearing MgO using hybrid functional

    Science.gov (United States)

    Cheng, Ya; Wang, Xianlong; Zhang, Jie; Yang, Kaishuai; Zhang, Chuanguo; Zeng, Zhi; Lin, Haiqin

    2018-04-01

    Pressure-induced spin crossover behaviors of Fe-bearing MgO were widely investigated by using an LDA  +  U functional for describing the strongly correlated Fe–O bonding. Moreover, the simulated spin crossover pressures depend on the applied U values, which are sensitive to environments and parameters. In this work, the spin crossover pressures of (Mg1‑x ,Fe x )O are investigated by using the hybrid functional with a uniform parameter. Our results indicate that the spin crossover pressures increase with increasing iron concentration. For example, the spin crossover pressure of (Mg0.03125,Fe0.96875)O and FeO was 56 GPa and 127 GPa, respectively. The calculated crossover pressures agreed well with the experimental observations. Therefore, the hybrid functional should be an effective method for describing the pressure-induced spin crossover behaviors in transition metal oxides.

  14. Dependence of Excited State Potential Energy Surfaces on the Spatial Overlap of the Kohn-Sham Orbitals and the Amount of Nonlocal Hartree-Fock Exchange in Time-Dependent Density Functional Theory.

    Science.gov (United States)

    Plötner, Jürgen; Tozer, David J; Dreuw, Andreas

    2010-08-10

    Time-dependent density functional theory (TDDFT) with standard GGA or hybrid exchange-correlation functionals is not capable of describing the potential energy surface of the S1 state of Pigment Yellow 101 correctly; an additional local minimum is observed at a twisted geometry with substantial charge transfer (CT) character. To investigate the influence of nonlocal exact orbital (Hartree-Fock) exchange on the shape of the potential energy surface of the S1 state in detail, it has been computed along the twisting coordinate employing the standard BP86, B3LYP, and BHLYP xc-functionals as well as the long-range separated (LRS) exchange-correlation (xc)-functionals LC-BOP, ωB97X, ωPBE, and CAM-B3LYP and compared to RI-CC2 benchmark results. Additionally, a recently suggested Λ-parameter has been employed that measures the amount of CT in an excited state by calculating the spatial overlap of the occupied and virtual molecular orbitals involved in the transition. Here, the error in the calculated S1 potential energy curves at BP86, B3LYP, and BHLYP can be clearly related to the Λ-parameter, i.e., to the extent of charge transfer. Additionally, it is demonstrated that the CT problem is largely alleviated when the BHLYP xc-functional is employed, although it still exhibits a weak tendency to underestimate the energy of CT states. The situation improves drastically when LRS-functionals are employed within TDDFT excited state calculations. All tested LRS-functionals give qualitatively the correct potential energy curves of the energetically lowest excited states of P. Y. 101 along the twisting coordinate. While LC-BOP and ωB97X overcorrect the CT problem and now tend to give too large excitation energies compared to other non-CT states, ωPBE and CAM-B3LYP are in excellent agreement with the RI-CC2 results, with respect to both the correct shape of the potential energy curve as well as the absolute values of the calculated excitation energies.

  15. The X3LYP extended density functional for accurate descriptions of nonbond interactions, spin states, and thermochemical properties

    OpenAIRE

    Xu, Xin; Goddard, William A., III

    2004-01-01

    We derive the form for an exact exchange energy density for a density decaying with Gaussian-like behavior at long range. Based on this, we develop the X3LYP (extended hybrid functional combined with Lee-Yang-Parr correlation functional) extended functional for density functional theory to significantly improve the accuracy for hydrogen-bonded and van der Waals complexes while also improving the accuracy in heats of formation, ionization potentials, electron affinities, and total atomic energ...

  16. Shear Alfvén Wave with Quantum Exchange-Correlation Effects in Plasmas

    Science.gov (United States)

    Mir, Zahid; Jamil, M.; Rasheed, A.; Asif, M.

    2017-09-01

    The dust shear Alfvén wave is studied in three species dusty quantum plasmas. The quantum effects are incorporated through the Fermi degenerate pressure, tunneling potential, and in particular the exchange-correlation potential. The significance of exchange-correlation potential is pointed out by a graphical description of the dispersion relation, which shows that the exchange potential magnifies the phase speed. The low-frequency shear Alfvén wave is studied while considering many variables. The shear Alfvén wave gains higher phase speed at the range of small angles for the upper end of the wave vector spectrum. The increasing dust charge and the external magnetic field reflect the increasing tendency of phase speed. This study may explain many natural mechanisms associated with long wavelength radiations given in the summary.

  17. Numerical Study of Condensation Heat Exchanger Design in a Cooling jacket: Correlation Investigation

    International Nuclear Information System (INIS)

    Kim, Myoung Jun; Lee, Hee Joon; Kang, Han Ok; Lee, Tae Ho; Park, Cheon Tae

    2013-01-01

    In this study, condensing heat transfer correlation of TSCON is evaluated with the existing experimental data set to design condensation heat exchanger without noncondensable gas effect (pure steam condensation) in a cooling jacket. From the investigation of the existing condensation heat transfer correlation to the existing experimental data, the improved Shah's correlation showed most satisfactory result for the condensation heat transfer coefficient with experimental data of Khun in a cooling jacket, whereas the Shah's correlation with experimental data of Lee. Lee et al. reported the improved Shah correlation gave us the best predictor for the condensation heat transfer data of Kim and Henderson in a subcooled and saturated water pool. They suggested the improved Shah correlation should be adopted as condensation heat transfer module in TSCON(Thermal Sizing of CONdenser) to design condensation heat exchanger in secondary passive cooling system of nuclear plant

  18. Functional PMS2 hybrid alleles containing a pseudogene-specific missense variant trace back to a single ancient intrachromosomal recombination event.

    Science.gov (United States)

    Ganster, Christina; Wernstedt, Annekatrin; Kehrer-Sawatzki, Hildegard; Messiaen, Ludwine; Schmidt, Konrad; Rahner, Nils; Heinimann, Karl; Fonatsch, Christa; Zschocke, Johannes; Wimmer, Katharina

    2010-05-01

    Sequence exchange between PMS2 and its pseudogene PMS2CL, embedded in an inverted duplication on chromosome 7p22, has been reported to be an ongoing process that leads to functional PMS2 hybrid alleles containing PMS2- and PMS2CL-specific sequence variants at the 5'-and the 3'-end, respectively. The frequency of PMS2 hybrid alleles, their biological significance, and the mechanisms underlying their formation are largely unknown. Here we show that overall hybrid alleles account for one-third of 384 PMS2 alleles analyzed in individuals of different ethnic backgrounds. Depending on the population, 14-60% of hybrid alleles carry PMS2CL-specific sequences in exons 13-15, the remainder only in exon 15. We show that exons 13-15 hybrid alleles, named H1 hybrid alleles, constitute different haplotypes but trace back to a single ancient intrachromosomal recombination event with crossover. Taking advantage of an ancestral sequence variant specific for all H1 alleles we developed a simple gDNA-based polymerase chain reaction (PCR) assay that can be used to identify H1-allele carriers with high sensitivity and specificity (100 and 99%, respectively). Because H1 hybrid alleles harbor missense variant p.N775S of so far unknown functional significance, we assessed the H1-carrier frequency in 164 colorectal cancer patients. So far, we found no indication that the variant plays a major role with regard to cancer susceptibility. (c) 2010 Wiley-Liss, Inc.

  19. Behaviour of the electron density near an impurity with exchange and correlation

    International Nuclear Information System (INIS)

    Adawi, I.; Godwin, V.E.

    1982-09-01

    The behaviour of the electron density n(r) and potential energy V(r) near an impurity of charge Z is studied in the linear response theory of metals with exchange and correlation. The leading two terms in nsub(odd)(r) and the first three terms in Vsub(odd)(r) are the same as in the Lindhard theory, but corrections appear in the higher terms of the odd powers expansions of these functions. In all quantum linear response theories, the derivative n'(0)=-2Zn 0 /a 0 where n 0 is the free electron gas density and a 0 is the Bohr radius. (author)

  20. Practical auxiliary basis implementation of Rung 3.5 functionals

    International Nuclear Information System (INIS)

    Janesko, Benjamin G.; Scalmani, Giovanni; Frisch, Michael J.

    2014-01-01

    Approximate exchange-correlation functionals for Kohn-Sham density functional theory often benefit from incorporating exact exchange. Exact exchange is constructed from the noninteracting reference system's nonlocal one-particle density matrix γ(r -vector ,r -vector ′). Rung 3.5 functionals attempt to balance the strengths and limitations of exact exchange using a new ingredient, a projection of γ(r -vector ,r -vector ′) onto a semilocal model density matrix γ SL (ρ(r -vector ),∇ρ(r -vector ),r -vector −r -vector ′). γ SL depends on the electron density ρ(r -vector ) at reference point r -vector , and is closely related to semilocal model exchange holes. We present a practical implementation of Rung 3.5 functionals, expanding the r -vector −r -vector ′ dependence of γ SL in an auxiliary basis set. Energies and energy derivatives are obtained from 3D numerical integration as in standard semilocal functionals. We also present numerical tests of a range of properties, including molecular thermochemistry and kinetics, geometries and vibrational frequencies, and bandgaps and excitation energies. Rung 3.5 functionals typically provide accuracy intermediate between semilocal and hybrid approximations. Nonlocal potential contributions from γ SL yield interesting successes and failures for band structures and excitation energies. The results enable and motivate continued exploration of Rung 3.5 functional forms

  1. Spin-Density Functionals from Current-Density Functional Theory and Vice Versa: A Road towards New Approximations

    International Nuclear Information System (INIS)

    Capelle, K.; Gross, E.

    1997-01-01

    It is shown that the exchange-correlation functional of spin-density functional theory is identical, on a certain set of densities, with the exchange-correlation functional of current-density functional theory. This rigorous connection is used to construct new approximations of the exchange-correlation functionals. These include a conceptually new generalized-gradient spin-density functional and a nonlocal current-density functional. copyright 1997 The American Physical Society

  2. Numerical Study of Condensation Heat Exchanger Design in a Cooling jacket: Correlation Investigation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Myoung Jun; Lee, Hee Joon [Kookmin Univ., Seoul (Korea, Republic of); Kang, Han Ok; Lee, Tae Ho; Park, Cheon Tae [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2013-10-15

    In this study, condensing heat transfer correlation of TSCON is evaluated with the existing experimental data set to design condensation heat exchanger without noncondensable gas effect (pure steam condensation) in a cooling jacket. From the investigation of the existing condensation heat transfer correlation to the existing experimental data, the improved Shah's correlation showed most satisfactory result for the condensation heat transfer coefficient with experimental data of Khun in a cooling jacket, whereas the Shah's correlation with experimental data of Lee. Lee et al. reported the improved Shah correlation gave us the best predictor for the condensation heat transfer data of Kim and Henderson in a subcooled and saturated water pool. They suggested the improved Shah correlation should be adopted as condensation heat transfer module in TSCON(Thermal Sizing of CONdenser) to design condensation heat exchanger in secondary passive cooling system of nuclear plant.

  3. 78 FR 21642 - Self-Regulatory Organizations; Chicago Board Options Exchange, Incorporated; Order Granting...

    Science.gov (United States)

    2013-04-11

    ..., the Exchange provided rationale for terminating the HAL auction early and cancelling of the market... proposes to modify Exchange Rule 6.14A, ``Hybrid Agency Liaison (``HAL''). This functionality provides... bid or offer (``BBO''),\\28\\ HAL electronically exposes the order \\29\\ at the NBBO price to allow...

  4. Heterosis and correlation in interspecific and intraspecific hybrids of cotton.

    Science.gov (United States)

    Munir, S; Hussain, S B; Manzoor, H; Quereshi, M K; Zubair, M; Nouman, W; Shehzad, A N; Rasul, S; Manzoor, S A

    2016-06-24

    Interspecific and intraspecific hybrids show varying degrees of heterosis for yield and yield components. Yield-component traits have complex genetic relationships with each other. To determine the relationship of yield-component traits and fiber traits with seed cotton yield, six lines (Bt. CIM-599, CIM-573, MNH-786, CIM-554, BH-167, and GIZA-7) and three test lines (MNH-886, V4, and CIM-557) were crossed in a line x tester mating design. Heterosis was observed for seed cotton yield, fiber traits, and for other yield-component traits. Heterosis in interspecific hybrids for seed cotton yield was more prominent than in intraspecific hybrids. The interspecific hybrid Giza-7 x MNH-886 had the highest heterosis (114.77), while among intraspecific hybrids, CIM-554 x CIM-557 had the highest heterosis (61.29) for seed cotton yield. A major trait contributing to seed cotton yield was bolls/plant followed by boll weight. Correlation studies revealed that bolls/plant, boll weight, lint weight/boll, lint index, seed index, lint/seed, staple length, and staple strength were significantly and positively associated with seed cotton yield. Selection based on boll weight, boll number, lint weight/boll, and lint index will be helpful for improving cotton seed yield.

  5. Application of gradient-corrected density functional theory to the structures and thermochemistries of ScF3, TiF4, VF5, and CrF6

    International Nuclear Information System (INIS)

    Russo, T.V.; Martin, R.L.; Jeffrey Hay, P.

    1995-01-01

    Density functional theory (DFT) and Hartree--Fock (HF) calculations are reported for the family of transition metal fluorides ScF 3 , TiF 4 , VF 5 , and CrF 6 . Both HF and the local-density approximation (LDA) yield excellent agreement with experimental bond lengths, while the B-LYP gradient-corrected density functional gives bond lengths 0.04-0.05 A too long. An investigation of various combinations of exchange and correlation functionals shows that, for this series, the origin of this behavior lies in the Becke exchange functional. Much improved bond distances are found using the hybrid HF/DFT functional advocated by Becke. This approximation also leads to much improved thermochemistries. The LDA overestimates average bond energies in this series by 30-40 kcal/mol, whereas the B-LYP functional overbinds by only ∼8-12 kcal/mol, and the hybrid HF/DFT method overbinds by only ∼2 kcal/mol. The hybrid method predicts the octahedral isomer of CrF 6 to be more stable than the trigonal prismatic form by 14 kcal/mol. Comparison of theoretical vibrational frequencies with experiment supports the assignment of an octahedral geometry

  6. Hidden symmetry of four-point correlation functions and amplitudes in N=4 SYM

    CERN Document Server

    Eden, Burkhard; Korchemsky, Gregory P; Sokatchev, Emery

    2012-01-01

    We study the four-point correlation function of stress-tensor supermultiplets in N=4 SYM using the method of Lagrangian insertions. We argue that, as a corollary of N=4 superconformal symmetry, the resulting all-loop integrand possesses an unexpected complete symmetry under the exchange of the four external and all the internal (integration) points. This alone allows us to predict the integrand of the three-loop correlation function up to four undetermined constants. Further, exploiting the conjectured amplitude/correlation function duality, we are able to fully determine the three-loop integrand in the planar limit. We perform an independent check of this result by verifying that it is consistent with the operator product expansion, in particular that it correctly reproduces the three-loop anomalous dimension of the Konishi operator. As a byproduct of our study, we also obtain the three-point function of two half-BPS operators and one Konishi operator at three-loop level. We use the same technique to work ou...

  7. Correlation of the Dzyaloshinskii–Moriya interaction with Heisenberg exchange and orbital asphericity

    KAUST Repository

    Kim, Sanghoon

    2018-04-19

    Chiral spin textures of a ferromagnetic layer in contact to a heavy non-magnetic metal, such as Néel-type domain walls and skyrmions, have been studied intensively because of their potential for future nanomagnetic devices. The Dyzaloshinskii–Moriya interaction (DMI) is an essential phenomenon for the formation of such chiral spin textures. In spite of recent theoretical progress aiming at understanding the microscopic origin of the DMI, an experimental investigation unravelling the physics at stake is still required. Here we experimentally demonstrate the close correlation of the DMI with the anisotropy of the orbital magnetic moment and with the magnetic dipole moment of the ferromagnetic metal in addition to Heisenberg exchange. The density functional theory and the tight-binding model calculations reveal that inversion symmetry breaking with spin–orbit coupling gives rise to the orbital-related correlation. Our study provides the experimental connection between the orbital physics and the spin–orbit-related phenomena, such as DMI.

  8. Density functional for van der Waals forces accounts for hydrogen bond in benchmark set of water hexamers

    DEFF Research Database (Denmark)

    Kelkkanen, Kari André; Lundqvist, Bengt; Nørskov, Jens Kehlet

    2009-01-01

    A recent extensive study has investigated how various exchange-correlation (XC) functionals treat hydrogen bonds in water hexamers and has shown traditional generalized gradient approximation and hybrid functionals used in density-functional (DF) theory to give the wrong dissociation-energy trend...... of low-lying isomers and van der Waals (vdW) dispersion forces to give key contributions to the dissociation energy. The question raised whether functionals that incorporate vdW forces implicitly into the XC functional predict the correct lowest-energy structure for the water hexamer and yield accurate...

  9. Photolithography and Fluorescence Correlation Spectroscopy used to examine the rates of exchange in reverse micelle systems

    Science.gov (United States)

    Norris, Zach; Mawson, Cara; Johnson, Kyron; Kessler, Sarah; Rebecca, Anne; Wolf, Nathan; Lim, Michael; Nucci, Nathaniel

    Reverse micelles are molecular complexes that encapsulate a nanoscale pool of water in a surfactant shell dissolved in non-polar solvent. These complexes have a wide range of applications, and in all cases, the degree to which reverse micelles (RM) exchange their contents is relevant for their use. Despite its importance, this aspect of RM behavior is poorly understood. Photolithography is employed here to create micro and nano scale fluidic systems in which mixing rates can be precisely measured using fluorescence correlation spectroscopy (FCS). Micro-channel patterns are etched using reactive ion etching process into a layer of silicon dioxide on crystalline silicon substrates. Solutions containing mixtures of reverse micelles, proteins, and fluorophores are placed into reservoirs in the patterns, while diffusion and exchange between RMs is monitored using a FCS system built from a modified confocal Raman spectrometer. Using this approach, the diffusion and exchange rates for RM systems are measured as a function of the components of the RM mixture. Funding provided by Rowan University.

  10. Relativistic four-component calculations of indirect nuclear spin-spin couplings with efficient evaluation of the exchange-correlation response kernel

    Energy Technology Data Exchange (ETDEWEB)

    Křístková, Anežka; Malkin, Vladimir G. [Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, SK-84536 Bratislava (Slovakia); Komorovsky, Stanislav; Repisky, Michal [Centre for Theoretical and Computational Chemistry, University of Tromsø - The Arctic University of Norway, N-9037 Tromsø (Norway); Malkina, Olga L., E-mail: olga.malkin@savba.sk [Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, SK-84536 Bratislava (Slovakia); Department of Inorganic Chemistry, Comenius University, Bratislava (Slovakia)

    2015-03-21

    In this work, we report on the development and implementation of a new scheme for efficient calculation of indirect nuclear spin-spin couplings in the framework of four-component matrix Dirac-Kohn-Sham approach termed matrix Dirac-Kohn-Sham restricted magnetic balance resolution of identity for J and K, which takes advantage of the previous restricted magnetic balance formalism and the density fitting approach for the rapid evaluation of density functional theory exchange-correlation response kernels. The new approach is aimed to speedup the bottleneck in the solution of the coupled perturbed equations: evaluation of the matrix elements of the kernel of the exchange-correlation potential. The performance of the new scheme has been tested on a representative set of indirect nuclear spin-spin couplings. The obtained results have been compared with the corresponding results of the reference method with traditional evaluation of the exchange-correlation kernel, i.e., without employing the fitted electron densities. Overall good agreement between both methods was observed, though the new approach tends to give values by about 4%-5% higher than the reference method. On the average, the solution of the coupled perturbed equations with the new scheme is about 8.5 times faster compared to the reference method.

  11. Relativistic four-component calculations of indirect nuclear spin-spin couplings with efficient evaluation of the exchange-correlation response kernel

    International Nuclear Information System (INIS)

    Křístková, Anežka; Malkin, Vladimir G.; Komorovsky, Stanislav; Repisky, Michal; Malkina, Olga L.

    2015-01-01

    In this work, we report on the development and implementation of a new scheme for efficient calculation of indirect nuclear spin-spin couplings in the framework of four-component matrix Dirac-Kohn-Sham approach termed matrix Dirac-Kohn-Sham restricted magnetic balance resolution of identity for J and K, which takes advantage of the previous restricted magnetic balance formalism and the density fitting approach for the rapid evaluation of density functional theory exchange-correlation response kernels. The new approach is aimed to speedup the bottleneck in the solution of the coupled perturbed equations: evaluation of the matrix elements of the kernel of the exchange-correlation potential. The performance of the new scheme has been tested on a representative set of indirect nuclear spin-spin couplings. The obtained results have been compared with the corresponding results of the reference method with traditional evaluation of the exchange-correlation kernel, i.e., without employing the fitted electron densities. Overall good agreement between both methods was observed, though the new approach tends to give values by about 4%-5% higher than the reference method. On the average, the solution of the coupled perturbed equations with the new scheme is about 8.5 times faster compared to the reference method

  12. Local electric dipole moments for periodic systems via density functional theory embedding.

    Science.gov (United States)

    Luber, Sandra

    2014-12-21

    We describe a novel approach for the calculation of local electric dipole moments for periodic systems. Since the position operator is ill-defined in periodic systems, maximally localized Wannier functions based on the Berry-phase approach are usually employed for the evaluation of local contributions to the total electric dipole moment of the system. We propose an alternative approach: within a subsystem-density functional theory based embedding scheme, subset electric dipole moments are derived without any additional localization procedure, both for hybrid and non-hybrid exchange-correlation functionals. This opens the way to a computationally efficient evaluation of local electric dipole moments in (molecular) periodic systems as well as their rigorous splitting into atomic electric dipole moments. As examples, Infrared spectra of liquid ethylene carbonate and dimethyl carbonate are presented, which are commonly employed as solvents in Lithium ion batteries.

  13. Current Issues in Finite-T Density-Functional Theory and Warm-Correlated Matter †

    Directory of Open Access Journals (Sweden)

    M. W. C. Dharma-wardana

    2016-03-01

    Full Text Available Finite-temperature density functional theory (DFT has become of topical interest, partly due to the increasing ability to create novel states of warm-correlated matter (WCM.Warm-dense matter (WDM, ultra-fast matter (UFM, and high-energy density matter (HEDM may all be regarded as subclasses of WCM. Strong electron-electron, ion-ion and electron-ion correlation effects and partial degeneracies are found in these systems where the electron temperature Te is comparable to the electron Fermi energy EF. Thus, many electrons are in continuum states which are partially occupied. The ion subsystem may be solid, liquid or plasma, with many states of ionization with ionic charge Zj. Quasi-equilibria with the ion temperature Ti ≠ Te are common. The ion subsystem in WCM can no longer be treated as a passive “external potential”, as is customary in T = 0 DFT dominated by solid-state theory or quantum chemistry. Many basic questions arise in trying to implement DFT for WCM. Hohenberg-Kohn-Mermin theory can be adapted for treating these systems if suitable finite-T exchange-correlation (XC functionals can be constructed. They are functionals of both the one-body electron density ne and the one-body ion densities ρj. Here, j counts many species of nuclei or charge states. A method of approximately but accurately mapping the quantum electrons to a classical Coulomb gas enables one to treat electron-ion systems entirely classically at any temperature and arbitrary spin polarization, using exchange-correlation effects calculated in situ, directly from the pair-distribution functions. This eliminates the need for any XC-functionals. This classical map has been used to calculate the equation of state of WDM systems, and construct a finite-T XC functional that is found to be in close agreement with recent quantum path-integral simulation data. In this review, current developments and concerns in finite-T DFT, especially in the context of non-relativistic warm

  14. Estimating time-varying conditional correlations between stock and foreign exchange markets

    Science.gov (United States)

    Tastan, Hüseyin

    2006-02-01

    This study explores the dynamic interaction between stock market returns and changes in nominal exchange rates. Many financial variables are known to exhibit fat tails and autoregressive variance structure. It is well-known that unconditional covariance and correlation coefficients also vary significantly over time and multivariate generalized autoregressive model (MGARCH) is able to capture the time-varying variance-covariance matrix for stock market returns and changes in exchange rates. The model is applied to daily Euro-Dollar exchange rates and two stock market indexes from the US economy: Dow-Jones Industrial Average Index and S&P500 Index. The news impact surfaces are also drawn based on the model estimates to see the effects of idiosyncratic shocks in respective markets.

  15. Hybrid IgG4/IgG4 Fc antibodies form upon 'Fab-arm' exchange as demonstrated by SDS-PAGE or size-exclusion chromatography

    NARCIS (Netherlands)

    Rispens, Theo; den Bleker, Tamara H.; Aalberse, Rob C.

    2010-01-01

    Human IgG4 antibodies are dynamic molecules that in vivo exchange half-molecules to become bispecific antibodies. Here we show that IgG4 antibodies and IgG4 Fc fragments similarly exchange resulting in hybrid antibodies (a single Fab + Fc) with a molecular weight of ca. 100 kDa. These antibodies can

  16. Role of nonlocal exchange correlation in activated adsorption

    DEFF Research Database (Denmark)

    Hammer, Bjørk; Jacobsen, Karsten Wedel; Nørskov, Jens Kehlet

    1993-01-01

    The barrier for dissociative adsorption of H-2 on Al(110) has been calculated within the generalized gradient approximation. A pronounced increase of the barrier height is found compared with what is calculated in the local density approximation (LDA). The apparent LDA underestimation...... of the barrier height is shown to be intimately linked with the LDA underbinding of core electrons and we suggest it to be a general phenomenon not limited to the particular nonlocal exchange-correlation approximation used or the particular system studied....

  17. Hybrid optical CDMA-FSO communications network under spatially correlated gamma-gamma scintillation.

    Science.gov (United States)

    Jurado-Navas, Antonio; Raddo, Thiago R; Garrido-Balsells, José María; Borges, Ben-Hur V; Olmos, Juan José Vegas; Monroy, Idelfonso Tafur

    2016-07-25

    In this paper, we propose a new hybrid network solution based on asynchronous optical code-division multiple-access (OCDMA) and free-space optical (FSO) technologies for last-mile access networks, where fiber deployment is impractical. The architecture of the proposed hybrid OCDMA-FSO network is thoroughly described. The users access the network in a fully asynchronous manner by means of assigned fast frequency hopping (FFH)-based codes. In the FSO receiver, an equal gain-combining technique is employed along with intensity modulation and direct detection. New analytical formalisms for evaluating the average bit error rate (ABER) performance are also proposed. These formalisms, based on the spatially correlated gamma-gamma statistical model, are derived considering three distinct scenarios, namely, uncorrelated, totally correlated, and partially correlated channels. Numerical results show that users can successfully achieve error-free ABER levels for the three scenarios considered as long as forward error correction (FEC) algorithms are employed. Therefore, OCDMA-FSO networks can be a prospective alternative to deliver high-speed communication services to access networks with deficient fiber infrastructure.

  18. Ion-exchange properties of zeolite/glass hybrid materials

    International Nuclear Information System (INIS)

    Taira, Nobuyuki; Yoshida, Kohei; Fukushima, Takuya

    2017-01-01

    Hybrid materials were prepared from ground glass powder and various zeolites such as A-type, mordenite, X-type, and Y-type zeolites, and their ion removal effect was investigated. The hybrid materials of A-type, Y-type, and mordenite zeolites showed similar Sr"2"+ removal rates from aqueous solutions. The removal rate of Sr"2"+ ions increased as the amount of zeolite in the hybrid materials increased. Compared with other hybrid materials, the hybrid materials of X-type zeolite showed higher Sr"2"+ removal rates, especially for zeolite content greater than 25%. As the amount of X-type zeolite in the hybrid materials increased, the Sr"2"+ removal rate increased greatly, with a 100% removal rate when the content of X-type zeolite exceeded 62.5%. (author)

  19. Effects of correlated hybridization in the single-impurity Anderson model

    Science.gov (United States)

    Líbero, Valter; Veiga, Rodrigo

    2013-03-01

    The development of new materials often dependents on the theoretical foundations which study the microscopic matter, i.e., the way atoms interact and create distinct configurations. Among the interesting materials, those with partially filled d or f orbitals immersed in nonmagnetic metals have been described by the Anderson model, which takes into account Coulomb correlation (U) when a local level (energy Ed) is doubled occupied, and an electronic hybridization between local levels and conduction band states. In addition, here we include a correlated hybridization term, which depends on the local-level occupation number involved. This term breaks particle-hole symmetry (even when U + 2Ed = 0), enhances charge fluctuations on local levels and as a consequence strongly modifies the crossover between the Hamiltonian fixed-points, even suppressing one or other. We exemplify these behaviors showing data obtained from the Numerical Renormalization Group (NRG) computation for the impurity temperature-dependent specific heat, entropy and magnetic susceptibility. The interleaving procedure is used to recover the continuum spectrum after the NRG-logarithmic discretization of the conduction band. Fundação de Amparo à Pesquisa do Estado de São Paulo - FAPESP.

  20. Bond breaking and bond formation: how electron correlation is captured in many-body perturbation theory and density-functional theory.

    Science.gov (United States)

    Caruso, Fabio; Rohr, Daniel R; Hellgren, Maria; Ren, Xinguo; Rinke, Patrick; Rubio, Angel; Scheffler, Matthias

    2013-04-05

    For the paradigmatic case of H(2) dissociation, we compare state-of-the-art many-body perturbation theory in the GW approximation and density-functional theory in the exact-exchange plus random-phase approximation (RPA) for the correlation energy. For an unbiased comparison and to prevent spurious starting point effects, both approaches are iterated to full self-consistency (i.e., sc-RPA and sc-GW). The exchange-correlation diagrams in both approaches are topologically identical, but in sc-RPA they are evaluated with noninteracting and in sc-GW with interacting Green functions. This has a profound consequence for the dissociation region, where sc-RPA is superior to sc-GW. We argue that for a given diagrammatic expansion, sc-RPA outperforms sc-GW when it comes to bond breaking. We attribute this to the difference in the correlation energy rather than the treatment of the kinetic energy.

  1. Multifractal detrended Cross Correlation Analysis of Foreign Exchange and SENSEX fluctuation in Indian perspective

    Science.gov (United States)

    Dutta, Srimonti; Ghosh, Dipak; Chatterjee, Sucharita

    2016-12-01

    The manuscript studies autocorrelation and cross correlation of SENSEX fluctuations and Forex Exchange Rate in respect to Indian scenario. Multifractal detrended fluctuation analysis (MFDFA) and multifractal detrended cross correlation analysis (MFDXA) were employed to study the correlation between the two series. It was observed that the two series are strongly cross correlated. The change of degree of cross correlation with time was studied and the results are interpreted qualitatively.

  2. Correlation Functions and Power Spectra

    DEFF Research Database (Denmark)

    Larsen, Jan

    2006-01-01

    The present lecture note is a supplement to the textbook Digital Signal Processing by J. Proakis and D.G. Manolakis used in the IMM/DTU course 02451 Digital Signal Processing and provides an extended discussion of correlation functions and power spectra. The definitions of correlation functions...... and spectra for discrete-time and continuous-time (analog) signals are pretty similar. Consequently, we confine the discussion mainly to real discrete-time signals. The Appendix contains detailed definitions and properties of correlation functions and spectra for analog as well as discrete-time signals....... It is possible to define correlation functions and associated spectra for aperiodic, periodic and random signals although the interpretation is different. Moreover, we will discuss correlation functions when mixing these basic signal types. In addition, the note include several examples for the purpose...

  3. Pair Correlation Function Integrals

    DEFF Research Database (Denmark)

    Wedberg, Nils Hejle Rasmus Ingemar; O'Connell, John P.; Peters, Günther H.J.

    2011-01-01

    We describe a method for extending radial distribution functions obtained from molecular simulations of pure and mixed molecular fluids to arbitrary distances. The method allows total correlation function integrals to be reliably calculated from simulations of relatively small systems. The long......-distance behavior of radial distribution functions is determined by requiring that the corresponding direct correlation functions follow certain approximations at long distances. We have briefly described the method and tested its performance in previous communications [R. Wedberg, J. P. O’Connell, G. H. Peters......, and J. Abildskov, Mol. Simul. 36, 1243 (2010); Fluid Phase Equilib. 302, 32 (2011)], but describe here its theoretical basis more thoroughly and derive long-distance approximations for the direct correlation functions. We describe the numerical implementation of the method in detail, and report...

  4. Hydrogels from Biopolymer Hybrid for Biomedical, Food, and Functional Food Applications

    Directory of Open Access Journals (Sweden)

    Robert C. Spiro

    2012-04-01

    Full Text Available Hybrid hydrogels from biopolymers have been applied for various indications across a wide range of biomedical, pharmaceutical, and functional food industries. In particular, hybrid hydrogels synthesized from two biopolymers have attracted increasing attention. The inclusion of a second biopolymer strengthens the stability of resultant hydrogels and enriches its functionalities by bringing in new functional groups or optimizing the micro-environmental conditions for certain biological and biochemical processes. This article presents approaches that have been used by our groups to synthesize biopolymer hybrid hydrogels for effective uses for immunotherapy, tissue regeneration, food and functional food applications. The research has achieved some challenging results, such as stabilizing physical structure, increasing mucoadhesiveness, and the creation of an artificial extracellular matrix to aid in guiding tissue differentiation.

  5. Hybride magnetic nanostructure based on amino acids functionalized polypyrrole

    Energy Technology Data Exchange (ETDEWEB)

    Nan, Alexandrina, E-mail: alexandrina.nan@itim-cj.ro; Bunge, Alexander; Turcu, Rodica [National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat, 400293 Cluj-Napoca (Romania)

    2015-12-23

    Conducting polypyrrole is especially promising for many commercial applications because of its unique optical, electric, thermal and mechanical properties. We report the synthesis and characterization of novel pyrrole functionalized monomers and core-shell hybrid nanostructures, consisting of a conjugated polymer layer (amino acids functionalized pyrrole copolymers) and a magnetic nanoparticle core. For functionalization of the pyrrole monomer we used several amino acids: tryptophan, leucine, phenylalanine, serine and tyrosine. These amino acids were linked via different types of hydrophobic linkers to the nitrogen atom of the pyrrole monomer. The magnetic core-shell hybrid nanostructures are characterized by various methods such as FTIR spectroscopy, transmission electron microscopy (TEM) and magnetic measurements.

  6. Mixed matrix microporous hollow fibers with ion-exchange functionality

    NARCIS (Netherlands)

    Kiyono, R.; Kiyono, R.; Koops, G.H.; Wessling, Matthias; Strathmann, H.

    2004-01-01

    Heterogeneous hollow fiber membranes with cation exchange functionality are prepared using a wet spinning technique. The spinning dope solutions are prepared by dispersing finely ground cation ion-exchange resin (CER) particles in an N-methyl pyrrolidone solution of polysulfone (PSF). The polymer

  7. Local density approximation for exchange in excited-state density functional theory

    OpenAIRE

    Harbola, Manoj K.; Samal, Prasanjit

    2004-01-01

    Local density approximation for the exchange energy is made for treatment of excited-states in density-functional theory. It is shown that taking care of the state-dependence of the LDA exchange energy functional leads to accurate excitation energies.

  8. Characteristic of Hybrid Cellulose-Amino Functionalized POSS-Silica Nanocomposite and Antimicrobial Activity

    Directory of Open Access Journals (Sweden)

    Sivalingam Ramesh

    2015-01-01

    Full Text Available Recently, cellulose has much attention as an emerging renewable nanomaterial which holds promising properties having unique piezoelectricity, insulating, and biodegradable nature for various applications. Also, the modified properties of cellulose by appropriate chemical modifications in various functional groups with outstanding properties or significantly improved physical, chemical, biological, and electronic properties will widen the way for it to be utilized in different usages. Therefore, in this paper, cellulose-functionalized polyhedral oligomeric silsesquioxanes (POSS based materials were considered an important class of high-performance hybrid nanocomposite materials. To functionalize the regenerated cellulose, amino functionalized POSS material was synthesized via sol-gel covalent crosslinking process in presence of amino coupling agent. In this reaction, tetraethoxsilane (TEOS and γ-aminopropyltriethoxy silane (γ-APTES as coupling agent for metal precursors were selected. The chemical structure of cellulose-amine functionalized bonding and covalent crosslinking hybrids was confirmed by FTIR and 1H NMR spectral analysis. From the TEM results, well-dispersed hybrid cellulose-functionalized POSS-silica composites are observed. The resulting cellulose-POSS-silica hybrid nanocomposites materials provided significantly improved the optical transparency, and thermal and morphological properties to compare the cellulose-silica hybrid materials. Further, antimicrobial test against pathogenic bacteria was carried out.

  9. The electricity exchange. On the organisation and latent functions of electricity exchange trading as seen from the viewpoint of market sociology

    International Nuclear Information System (INIS)

    Giacovelli, Sebastian

    2014-01-01

    Electricity exchange trading in Germany has existed since the year 2000. Since this time, the Leipzig electricity exchange, a reference market for off-exchange electricity trading, has operated in an environment marked by both criticism and acceptance. Taking this field of controversy as a point of departure the present empirical study in market sociology undertakes to investigate the organisation and latent functions of electricity exchange trading. The ensuing analysis provides answers to questions as to how prices are formed on the electricity exchange and what officially incommunicable functions are served by price formation on exchanges.

  10. Hybrid ICA-Seed-Based Methods for fMRI Functional Connectivity Assessment: A Feasibility Study

    Directory of Open Access Journals (Sweden)

    Robert E. Kelly

    2010-01-01

    Full Text Available Brain functional connectivity (FC is often assessed from fMRI data using seed-based methods, such as those of detecting temporal correlation between a predefined region (seed and all other regions in the brain; or using multivariate methods, such as independent component analysis (ICA. ICA is a useful data-driven tool, but reproducibility issues complicate group inferences based on FC maps derived with ICA. These reproducibility issues can be circumvented with hybrid methods that use information from ICA-derived spatial maps as seeds to produce seed-based FC maps. We report results from five experiments to demonstrate the potential advantages of hybrid ICA-seed-based FC methods, comparing results from regressing fMRI data against task-related a priori time courses, with “back-reconstruction” from a group ICA, and with five hybrid ICA-seed-based FC methods: ROI-based with (1 single-voxel, (2 few-voxel, and (3 many-voxel seed; and dual-regression-based with (4 single ICA map and (5 multiple ICA map seed.

  11. Beyond the Random Phase Approximation for the Electron Correlation Energy: The Importance of Single Excitations

    OpenAIRE

    Ren, Xinguo; Rinke, Patrick; Tkatchenko, Alexandre; Scheffler, Matthias

    2010-01-01

    The random-phase approximation (RPA) for the electron correlation energy, combined with the exact-exchange (EX) energy, represents the state-of-the-art exchange-correlation functional within density-functional theory. However, the standard RPA practice-evaluating both the EX and the RPA correlation energies using Kohn-Sham (KS) orbitals from local or semilocal exchange-correlation functionals-leads to a systematic underbinding of molecules and solids. Here we demonstrate that this behavior ca...

  12. Importance of finite-temperature exchange correlation for warm dense matter calculations.

    Science.gov (United States)

    Karasiev, Valentin V; Calderín, Lázaro; Trickey, S B

    2016-06-01

    The effects of an explicit temperature dependence in the exchange correlation (XC) free-energy functional upon calculated properties of matter in the warm dense regime are investigated. The comparison is between the Karasiev-Sjostrom-Dufty-Trickey (KSDT) finite-temperature local-density approximation (TLDA) XC functional [Karasiev et al., Phys. Rev. Lett. 112, 076403 (2014)PRLTAO0031-900710.1103/PhysRevLett.112.076403] parametrized from restricted path-integral Monte Carlo data on the homogeneous electron gas (HEG) and the conventional Monte Carlo parametrization ground-state LDA XC [Perdew-Zunger (PZ)] functional evaluated with T-dependent densities. Both Kohn-Sham (KS) and orbital-free density-functional theories are used, depending upon computational resource demands. Compared to the PZ functional, the KSDT functional generally lowers the dc electrical conductivity of low-density Al, yielding improved agreement with experiment. The greatest lowering is about 15% for T=15 kK. Correspondingly, the KS band structure of low-density fcc Al from the KSDT functional exhibits a clear increase in interband separation above the Fermi level compared to the PZ bands. In some density-temperature regimes, the deuterium equations of state obtained from the two XC functionals exhibit pressure differences as large as 4% and a 6% range of differences. However, the hydrogen principal Hugoniot is insensitive to the explicit XC T dependence because of cancellation between the energy and pressure-volume work difference terms in the Rankine-Hugoniot equation. Finally, the temperature at which the HEG becomes unstable is T≥7200 K for the T-dependent XC, a result that the ground-state XC underestimates by about 1000 K.

  13. Ground-state energies and highest occupied eigenvalues of atoms in exchange-only density-functional theory

    Science.gov (United States)

    Li, Yan; Harbola, Manoj K.; Krieger, J. B.; Sahni, Viraht

    1989-11-01

    The exchange-correlation potential of the Kohn-Sham density-functional theory has recently been interpreted as the work required to move an electron against the electric field of its Fermi-Coulomb hole charge distribution. In this paper we present self-consistent results for ground-state total energies and highest occupied eigenvalues of closed subshell atoms as obtained by this formalism in the exchange-only approximation. The total energies, which are an upper bound, lie within 50 ppm of Hartree-Fock theory for atoms heavier than Be. The highest occupied eigenvalues, as a consequence of this interpretation, approximate well the experimental ionization potentials. In addition, the self-consistently calculated exchange potentials are very close to those of Talman and co-workers [J. D. Talman and W. F. Shadwick, Phys. Rev. A 14, 36 (1976); K. Aashamar, T. M. Luke, and J. D. Talman, At. Data Nucl. Data Tables 22, 443 (1978)].

  14. Energy down converting organic fluorophore functionalized mesoporous silica hybrids for monolith-coated light emitting diodes

    Directory of Open Access Journals (Sweden)

    Markus Börgardts

    2017-04-01

    Full Text Available The covalent attachment of organic fluorophores in mesoporous silica matrices for usage as energy down converting phosphors without employing inorganic transition or rare earth metals is reported in this article. Triethoxysilylpropyl-substituted derivatives of the blue emitting perylene, green emitting benzofurazane, and red emitting Nile red were synthesized and applied in the synthesis of mesoporous hybrid materials by postsynthetic grafting to commercially available MCM-41. These individually dye-functionalized hybrid materials are mixed in variable ratios to furnish a powder capable of emitting white light with CIE chromaticity coordinates of x = 0.33, y = 0.33 and an external quantum yield of 4.6% upon irradiation at 410 nm. Furthermore, as a proof of concept two different device setups of commercially available UV light emitting diodes, are coated with silica monoliths containing the three triethoxysilylpropyl-substituted fluorophore derivatives. These coatings are able to convert the emitted UV light into light with correlated color temperatures of very cold white (41100 K, 10700 K as well as a greenish white emission with correlated color temperatures of about 5500 K.

  15. A Hybrid Algorithm for Optimizing Multi- Modal Functions

    Institute of Scientific and Technical Information of China (English)

    Li Qinghua; Yang Shida; Ruan Youlin

    2006-01-01

    A new genetic algorithm is presented based on the musical performance. The novelty of this algorithm is that a new genetic algorithm, mimicking the musical process of searching for a perfect state of harmony, which increases the robustness of it greatly and gives a new meaning of it in the meantime, has been developed. Combining the advantages of the new genetic algorithm, simplex algorithm and tabu search, a hybrid algorithm is proposed. In order to verify the effectiveness of the hybrid algorithm, it is applied to solving some typical numerical function optimization problems which are poorly solved by traditional genetic algorithms. The experimental results show that the hybrid algorithm is fast and reliable.

  16. The Correlation of Interphase Chromatin Structure with the Radiation-Induced Inter- and Intrachromosome Exchange Hotspots

    Science.gov (United States)

    Zhang, Ye; Mangala, Lingegowda S.; Purgason, Ashley M.; Hada, Megumi; Cucinotta, Francis A.; Wu, Honglu

    2011-01-01

    To investigate the relationship between chromosome aberrations induced by radiation and chromatin folding, we reconstructed three dimensional structure of chromosome 3 and measured the physical distances between different regions of the chromosome. Previously, we have investigated the location of breaks involved in inter- and intrachromosomal type exchange events in human chromosome 3, using the multicolor banding in situ hybridization (mBAND) technique. In human epithelial cells exposed to both low- and high-LET radiations in vitro, we reported that intra-chromosome exchanges occurred preferentially between a break in the 3p21 and one in the 3q11 regions, and the breaks involving in inter-chromosome exchanges occurred in two regions towards the telomeres of the chromosome. Exchanges were also observed between a break in 3p21 and one in 3q26, but few exchanges were observed between breaks in 3q11 and 3q26, even though the two regions are located on the same arm of the chromosome. In this study, human epithelial cells were fixed at G1 phase and the interphase cells were hybridized using the XCyte3 mBAND kit from MetaSystems. The z-section images of chromosome 3 were captured with a Leica and an LSM 510 Meta laser scanning confocal microscopes. A total of 100 chromosomes were analyzed. The reconstruction of three dimensional structure of interphase chromosome 3 with six different colored regions was achieved using the Imaris software. The relative distance between different regions was measured as well. We further analyzed fragile sites on the chromosome that have been identified in various types of cancers. The data showed that, in majority of the cells, the regions containing 3p21 and 3q11 are colocalized in the center of the chromosome, whereas, the regions towards the telomeres of the chromosome are either physically wrapping outside the chromosome center or with arms sticking out. Our results demonstrated that the distribution of breaks involved in radiation

  17. Functional Multiple-Set Canonical Correlation Analysis

    Science.gov (United States)

    Hwang, Heungsun; Jung, Kwanghee; Takane, Yoshio; Woodward, Todd S.

    2012-01-01

    We propose functional multiple-set canonical correlation analysis for exploring associations among multiple sets of functions. The proposed method includes functional canonical correlation analysis as a special case when only two sets of functions are considered. As in classical multiple-set canonical correlation analysis, computationally, the…

  18. The effect of exchange-correlation on change and stability of crystal structure

    International Nuclear Information System (INIS)

    Yazdani, A.; Niazi, M.; Alimardan, V.

    2007-01-01

    Since exchange interaction energy has effect on band structure via polarization of spin of free electron, then can directly effects formation crystal structure. Therefore exchange-correlation is able to have an effect on determination of crystal structure or its change and stability. This energy is subject to fluctuation range of electrons between conduction band and valance band or density of electrons which due to increase the entropy of system, via Gibss Energy .We investigated these factors: 1) Size of ions 2) Density of States 3) Range of inter atomic and pair-potential.

  19. Exchange of rotor components in functioning bacterial flagellar motor

    International Nuclear Information System (INIS)

    Fukuoka, Hajime; Inoue, Yuichi; Terasawa, Shun; Takahashi, Hiroto; Ishijima, Akihiko

    2010-01-01

    The bacterial flagellar motor is a rotary motor driven by the electrochemical potential of a coupling ion. The interaction between a rotor and stator units is thought to generate torque. The overall structure of flagellar motor has been thought to be static, however, it was recently proved that stators are exchanged in a rotating motor. Understanding the dynamics of rotor components in functioning motor is important for the clarifying of working mechanism of bacterial flagellar motor. In this study, we focused on the dynamics and the turnover of rotor components in a functioning flagellar motor. Expression systems for GFP-FliN, FliM-GFP, and GFP-FliG were constructed, and each GFP-fusion was functionally incorporated into the flagellar motor. To investigate whether the rotor components are exchanged in a rotating motor, we performed fluorescence recovery after photobleaching experiments using total internal reflection fluorescence microscopy. After photobleaching, in a tethered cell producing GFP-FliN or FliM-GFP, the recovery of fluorescence at the rotational center was observed. However, in a cell producing GFP-FliG, no recovery of fluorescence was observed. The transition phase of fluorescence intensity after full or partially photobleaching allowed the turnover of FliN subunits to be calculated as 0.0007 s -1 , meaning that FliN would be exchanged in tens of minutes. These novel findings indicate that a bacterial flagellar motor is not a static structure even in functioning state. This is the first report for the exchange of rotor components in a functioning bacterial flagellar motor.

  20. Approximate spin projected spin-unrestricted density functional theory method: Application to diradical character dependences of second hyperpolarizabilities

    Energy Technology Data Exchange (ETDEWEB)

    Nakano, Masayoshi, E-mail: mnaka@cheng.es.osaka-u.ac.jp; Minami, Takuya, E-mail: mnaka@cheng.es.osaka-u.ac.jp; Fukui, Hitoshi, E-mail: mnaka@cheng.es.osaka-u.ac.jp; Yoneda, Kyohei, E-mail: mnaka@cheng.es.osaka-u.ac.jp; Shigeta, Yasuteru, E-mail: mnaka@cheng.es.osaka-u.ac.jp; Kishi, Ryohei, E-mail: mnaka@cheng.es.osaka-u.ac.jp [Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Champagne, Benoît; Botek, Edith [Laboratoire de Chimie Théorique, Facultés Universitaires Notre-Dame de la Paix (FUNDP), rue de Bruxelles, 61, 5000 Namur (Belgium)

    2015-01-22

    We develop a novel method for the calculation and the analysis of the one-electron reduced densities in open-shell molecular systems using the natural orbitals and approximate spin projected occupation numbers obtained from broken symmetry (BS), i.e., spin-unrestricted (U), density functional theory (DFT) calculations. The performance of this approximate spin projection (ASP) scheme is examined for the diradical character dependence of the second hyperpolarizability (γ) using several exchange-correlation functionals, i.e., hybrid and long-range corrected UDFT schemes. It is found that the ASP-LC-UBLYP method with a range separating parameter μ = 0.47 reproduces semi-quantitatively the strongly-correlated [UCCSD(T)] result for p-quinodimethane, i.e., the γ variation as a function of the diradical character.

  1. Low-energy pion double charge exchange and nucleon-nucleon correlations in nuclei

    International Nuclear Information System (INIS)

    Leitch, M.J.

    1989-01-01

    Recent measurements of pion double-charge exchange (DCX) at energies 20 to 70 MeV are providing a new means for studying nucleon-nucleon correlations in nuclei. At these energies the nucleus is relatively transparent, allowing simpler theoretical models to be used in interpreting the data and leading to a clearer picture. Also the contribution to DCX of sequential charge-exchange scattering through the intermediate analog state is suppressed near 50 MeV and transitions through non-analog intermediate states become very important. Recent theoretical studies by several groups have shown that while transitions through the analog route involve relatively long nucleon-nucleon distances, those through non-analog intermediate states obtain nearly half their strength from nucleon pairs with less than 1 fermi separation. Thus DCX near 50 MeV is an excellent way to study short-range nucleon-nucleon correlations. 31 refs., 29 figs., 4 tabs

  2. Three-dimensional Reconstruction and Homogenization of Heterogeneous Materials Using Statistical Correlation Functions and FEM

    Energy Technology Data Exchange (ETDEWEB)

    Baniassadi, Majid; Mortazavi, Behzad; Hamedani, Amani; Garmestani, Hamid; Ahzi, Said; Fathi-Torbaghan, Madjid; Ruch, David; Khaleel, Mohammad A.

    2012-01-31

    In this study, a previously developed reconstruction methodology is extended to three-dimensional reconstruction of a three-phase microstructure, based on two-point correlation functions and two-point cluster functions. The reconstruction process has been implemented based on hybrid stochastic methodology for simulating the virtual microstructure. While different phases of the heterogeneous medium are represented by different cells, growth of these cells is controlled by optimizing parameters such as rotation, shrinkage, translation, distribution and growth rates of the cells. Based on the reconstructed microstructure, finite element method (FEM) was used to compute the effective elastic modulus and effective thermal conductivity. A statistical approach, based on two-point correlation functions, was also used to directly estimate the effective properties of the developed microstructures. Good agreement between the predicted results from FEM analysis and statistical methods was found confirming the efficiency of the statistical methods for prediction of thermo-mechanical properties of three-phase composites.

  3. Gas diffusion electrode based on electrospun Pani/CNF nanofibers hybrid for proton exchange membrane fuel cells (PEMFC) applications

    Energy Technology Data Exchange (ETDEWEB)

    Hezarjaribi, M.; Jahanshahi, M., E-mail: mjahan@nit.ac.ir; Rahimpour, A.; Yaldagard, M.

    2014-03-01

    A novel hybrid system has been investigated based on polyaniline/carbon nanofiber (Pani/CNF) electrospun nanofibers for modification of gas diffusion electrode (GDE) in proton exchange membrane fuel cells (PEMFC). Pani/CNF hybrid nanofibers were synthesized directly on carbon paper by electrospinning method. For preparation of catalyst ink, 20 wt.% Pt/C electrocatalyst with a platinum loading of 0.4 mg cm{sup −2} was prepared by polyol technique. SEM studies applied for morphological study of the modified GDE with hybrid nanofibers. This technique indicated that the electrospun nanofibers had a diameter of roughly 100 nm. XRD patterns also showed that the average size of Pt nanoparticles was about 2 nm. Subsequently, comparison of the hybrid electrode electrochemical behavior and 20 wt.% Pt/C commercial one was studied by cyclic voltammetry experiment. The electrochemical data indicated that the hybrid electrode exhibited higher current density (about 15 mA cm{sup −2}) and ESA (160 m{sup 2} gr{sup −1}) than commercial Pt/C with amount of about 10 mA cm{sup −2} and 114 m{sup 2} gr{sup −1}, respectively. The results herein demonstrate that Pani/CNF nanofibers can be used as a good alternative electrode material for PEMFCs.

  4. Non-covalently functionalized carbon nanostructures for synthesizing carbon-based hybrid nanomaterials.

    Science.gov (United States)

    Li, Haiqing; Song, Sing I; Song, Ga Young; Kim, Il

    2014-02-01

    Carbon nanostructures (CNSs) such as carbon nanotubes, graphene sheets, and nanodiamonds provide an important type of substrate for constructing a variety of hybrid nanomaterials. However, their intrinsic chemistry-inert surfaces make it indispensable to pre-functionalize them prior to immobilizing additional components onto their surfaces. Currently developed strategies for functionalizing CNSs include covalent and non-covalent approaches. Conventional covalent treatments often damage the structure integrity of carbon surfaces and adversely affect their physical properties. In contrast, the non-covalent approach offers a non-destructive way to modify CNSs with desired functional surfaces, while reserving their intrinsic properties. Thus far, a number of surface modifiers including aromatic compounds, small-molecular surfactants, amphiphilic polymers, and biomacromolecules have been developed to non-covalently functionalize CNS surfaces. Mediated by these surface modifiers, various functional components such as organic species and inorganic nanoparticles were further decorated onto their surfaces, resulting in versatile carbon-based hybrid nanomaterials with broad applications in chemical engineering and biomedical areas. In this review, the recent advances in the generation of such hybrid nanostructures based on non-covalently functionalized CNSs will be reviewed.

  5. Carbon dioxide exchange over agricultural landscape using eddy correlation and footprint modelling

    DEFF Research Database (Denmark)

    Søgaard, H.; Jensen, N.O.; Bøgh, E.

    2003-01-01

    Within an agricultural landscape of western Denmark, the carbon dioxide exchange was studied throughout a year (April 1998-March 1999). During the growing season, five eddy correlation systems were operated in parallel over some of the more important crops (winter wheat, winter barley, spring...

  6. [Correlation between gaseous exchange rate, body temperature, and mitochondrial protein content in the liver of mice].

    Science.gov (United States)

    Muradian, Kh K; Utko, N O; Mozzhukhina, T H; Pishel', I M; Litoshenko, O Ia; Bezrukov, V V; Fraĭfel'd, V E

    2002-01-01

    Correlative and regressive relations between the gaseous exchange, thermoregulation and mitochondrial protein content were analyzed by two- and three-dimensional statistics in mice. It has been shown that the pair wise linear methods of analysis did not reveal any significant correlation between the parameters under exploration. However, it became evident at three-dimensional and non-linear plotting for which the coefficients of multivariable correlation reached and even exceeded 0.7-0.8. The calculations based on partial differentiation of the multivariable regression equations allow to conclude that at certain values of VO2, VCO2 and body temperature negative relations between the systems of gaseous exchange and thermoregulation become dominating.

  7. Hybridization State Detection of DNA-Functionalized Gold Nanoparticles Using Hyperspectral Imaging

    Directory of Open Access Journals (Sweden)

    Richard C. Murdock

    2017-01-01

    Full Text Available Hyperspectral imaging has the unique ability of capturing spectral data for multiple wavelengths at each pixel in an image. This gives the ability to distinguish, with certainty, different nanomaterials and/or distinguish nanomaterials from biological materials. In this study, 4 nm and 13 nm gold nanoparticles (Au NPs were synthesized, functionalized with complimentary oligonucleotides, and hybridized to form large networks of NPs. Scattering spectra were collected from each sample (unfunctionalized, functionalized, and hybridized and evaluated. The spectra showed unique peaks for each size of Au NP sample and also exhibited narrowing and intensifying of the spectra as the NPs were functionalized and then subsequently hybridized. These spectra are different from normal aggregation effects where the LSPR and reflected spectrum broaden and are red-shifted. Rather, this appears to be dependent on the ability to control the interparticle distance through oligonucleotide length, which is also investigated through the incorporation of a poly-A spacer. Also, hybridized Au NPs were exposed to cells with no adverse effects and retained their unique spectral signatures. With the ability to distinguish between hybridization states at nearly individual NP levels, this could provide a new method of tracking the intracellular actions of nanomaterials as well as extracellular biosensing applications.

  8. Optimizing the specificity of nucleic acid hybridization.

    Science.gov (United States)

    Zhang, David Yu; Chen, Sherry Xi; Yin, Peng

    2012-01-22

    The specific hybridization of complementary sequences is an essential property of nucleic acids, enabling diverse biological and biotechnological reactions and functions. However, the specificity of nucleic acid hybridization is compromised for long strands, except near the melting temperature. Here, we analytically derived the thermodynamic properties of a hybridization probe that would enable near-optimal single-base discrimination and perform robustly across diverse temperature, salt and concentration conditions. We rationally designed 'toehold exchange' probes that approximate these properties, and comprehensively tested them against five different DNA targets and 55 spurious analogues with energetically representative single-base changes (replacements, deletions and insertions). These probes produced discrimination factors between 3 and 100+ (median, 26). Without retuning, our probes function robustly from 10 °C to 37 °C, from 1 mM Mg(2+) to 47 mM Mg(2+), and with nucleic acid concentrations from 1 nM to 5 µM. Experiments with RNA also showed effective single-base change discrimination.

  9. Novel acid-base hybrid membrane based on amine-functionalized reduced graphene oxide and sulfonated polyimide for vanadium redox flow battery

    International Nuclear Information System (INIS)

    Cao, Li; Sun, Qingqing; Gao, Yahui; Liu, Luntao; Shi, Haifeng

    2015-01-01

    A series of novel acid-base hybrid membranes (SPI/PEI-rGO) based on sulfonated polyimide (SPI) with polyethyleneimine-functionalized reduced graphene oxide (PEI-rGO) are prepared by a solution-casting method for vanadium redox flow battery (VRB). FT-IR and XPS results prove the successful fabrication of PEI-rGO and SPI/PEI-rGO hybrid membranes, which show a dense and homogeneous structure observed by SEM. The physicochemical properties such as water uptake, swelling ratio, ion exchange capacity, proton conductivity and vanadium ion permeability are well controlled by the incorporated PEI-rGO fillers. The interfacial-formed acid-base pairs between PEI-rGO and SPI matrix effectively reduce the swelling ratio and vanadium ion permeability, increasing the stability performance of the hybrid membranes. SPI/PEI-rGO-2 hybrid membrane exhibits a higher coulombic efficiency (CE, 95%) and energy efficiency (EE, 75.6%) at 40 mA cm −2 , as compared with Nafion 117 membrane (CE, 91% and EE, 66.8%). The self-discharge time of the VRB with SPI/PEI-rGO-2 hybrid membrane (80 h) is longer than that of Nafion 117 membrane (26 h), demonstrating the excellent blocking ability for vanadium ion. After 100 charge-discharge cycles, SPI/PEI-rGO-2 membrane exhibits the good stability under strong oxidizing and acid condition, proving that SPI/PEI-rGO acid-base hybrid membranes could be used as the promising candidates for VRB applications

  10. Hybrid functional calculation of electronic and phonon structure of BaSnO3

    International Nuclear Information System (INIS)

    Kim, Bog G.; Jo, J.Y.; Cheong, S.W.

    2013-01-01

    Barium stannate, BaSnO 3 (BSO), with a cubic perovskite structure, has been highlighted as a promising host material for the next generation transparent oxide electrodes. This study examined theoretically the electronic structure and phonon structure of BSO using hybrid density functional theory based on the HSE06 functional. The electronic structure results of BSO were corrected by extending the phonon calculations based on the hybrid density functional. The fundamental thermal properties were also predicted based on a hybrid functional calculation. Overall, a detailed understanding of the electronic structure, phonon modes and phonon dispersion of BSO will provide a theoretical starting-point for engineering applications of this material. - Graphical Abstract: (a) Crystal structure of BaSnO 3 . The center ball is Ba and small (red) ball on edge is oxygen and SnO 6 octahedrons are plotted as polyhedron. (b) Electronic band structure along the high symmetry point in the Brillouin zone using the HSE06 hybrid functional. (c) The phonon dispersion curve calculated using the HSE06 hybrid functional (d) Zone center lowest energy F 1u phonon mode. Highlights: ► We report the full hybrid functional calculation of not only the electronic structure but also the phonon structure for BaSnO 3 . ► The band gap calculation of HSE06 revealed an indirect gap with 2.48 eV. ► The effective mass at the conduction band minimum and valence band maximum was calculated. ► In addition, the phonon structure of BSO was calculated using the HSE06 functional. ► Finally, the heat capacity was calculated and compared with the recent experimental result.

  11. Organophosphonate functionalized silicon nanowires for DNA hybridization studies

    Energy Technology Data Exchange (ETDEWEB)

    Pedone, Daniel; Cattani Scholz, Anna; Birner, Stefan; Abstreiter, Gerhard [WSI, TU Muenchen (Germany); Dubey, Manish; Schwartz, Jeffrey [Princeton University, NJ (United States); Tornow, Marc [IHT, TU Braunschweig (Germany)

    2007-07-01

    Semiconductor nanowire field effect devices have great appeal for label-free sensing applications due to their sensitivity to surface potential changes that may originate from charged adsorbates. In addition to requiring high sensitivity, suitable passivation and functionalization of the semiconductor surface is obligatory. We have fabricated both freely suspended and oxide-supported silicon nanowires from Silicon-on-Insulator substrates using standard nanopatterning methods (EBL, RIE) and sacrificial oxide layer etching. Subsequent to nanofabrication, the devices were first coated with an hydroxyalkylphosphonate monolayer and then bound via bifunctional linker groups to single stranded DNA or PNA oligonucleotides, respectively. We investigated DNA hybridization on such functionalized nanowires using a difference resistance setup, where subtracting the reference signal from a second wire could be used to exclude most non-specific effects. A net change in surface potential on the order of a few mV could be detected upon addition of the complementary DNA strand. This surface potential change corresponds to the hybridization of about 10{sup 10}cm{sup -2} probe strands according to our model calculations that takes into account the entire hybrid system in electrolyte solution.

  12. Reaction mechanism and nuclear correlations study by low energy pion double charge exchange

    International Nuclear Information System (INIS)

    Weinfeld, Z.

    1993-06-01

    In pion double-charge-exchange (DCX) reactions, a positive (negative) pion is incident on a nucleus and a negative (positive) pion emerges. These reactions are of fundamental interest since the process must involve at least two nucleons in order to conserve charge. Although two nucleon processes are present in many reactions they are usually masked by the dominant single nucleon processes. DCX is unique in that respect since it is a two nucleon process in lowest order and thus may be sensitive to two-nucleon correlations. Measurements of low energy pion double-charge-exchange reactions to the double-isobaric-analog-state (DIAS) and ground-state (GS) of the residual nucleus provide new means for studying nucleon-nucleon correlations in nuclei. At low energies (T π 7/2 shell at energies ranging from 25 to 65 MeV. Cross sections were measured on 42,44,48 Ca, 46,50 Ti and 54 Fe. The calcium isotopes make a good set of nuclei on which to study the effects of correlations in DCX reactions

  13. Identification of novel CYP2D7-2D6 hybrids: non-functional and functional variants

    Directory of Open Access Journals (Sweden)

    Andrea Gaedigk

    2010-10-01

    Full Text Available Polymorphic expression of CYP2D6 contributes to the wide range of activity observed for this clinically important drug metabolizing enzyme. In this report we describe novel CYP2D7/2D6 hybrid genes encoding non-functional and functional CYP2D6 protein and a CYP2D7 variant that mimics a CYP2D7/2D6 hybrid gene. Five kb long PCR products encompassing the novel genes were entirely sequenced. A quantitative assay probing in different gene regions was employed to determine CYP2D6 and 2D7 copy number variations and the relative position of the hybrid genes within the locus was assessed by long-range PCR. In addition to the previously known CYP2D6*13 and *66 hybrids, we describe three novel non-functional CYP2D7-2D6 hybrids with gene switching in exon 2 (CYP2D6*79, intron 2 (CYP2D6*80 and intron 5 (CYP2D6*67. A CYP2D7-specific T-ins in exon 1 causes a detrimental frame shift. One subject revealed a CYP2D7 conversion in the 5’-flanking region of a CYP2D6*35 allele, was otherwise unaffected (designated CYP2D6*35B. Finally, three DNAs revealed a CYP2D7 gene with a CYP2D6-like region downstream of exon 9 (designated CYP2D7[REP6]. Quantitative copy number determination, sequence analyses and long-range PCR mapping were in agreement and excluded the presence of additional gene units. Undetected hybrid genes may cause over-estimation of CYP2D6 activity (CYP2D6*1/*1 vs *1/hybrid, etc, but may also cause results that may interfere with the genotype determination. Detection of hybrid events, ‘single’ and tandem, will contribute to more accurate phenotype prediction from genotype data.

  14. Estimation of Correlation Functions by Random Decrement

    DEFF Research Database (Denmark)

    Asmussen, J. C.; Brincker, Rune

    This paper illustrates how correlation functions can be estimated by the random decrement technique. Several different formulations of the random decrement technique, estimating the correlation functions are considered. The speed and accuracy of the different formulations of the random decrement...... and the length of the correlation functions. The accuracy of the estimates with respect to the theoretical correlation functions and the modal parameters are both investigated. The modal parameters are extracted from the correlation functions using the polyreference time domain technique....

  15. Using correlation functions as free decays

    DEFF Research Database (Denmark)

    Brincker, Rune; Amador, Sandro; Juul, Martin

    It is a general assumption in OMA that correlation functions are free decays. In multiple input OMA this assumption also implies that any column in the correlation function matrix is to be considered as multiple output free decays. This assumption is discussed in this paper together with issues...... concerning estimation and application of correlations functions in OMA....

  16. Exchangers man the pumps: Functional interplay between proton pumps and proton-coupled Ca exchangers.

    Science.gov (United States)

    Barkla, Bronwyn J; Hirschi, Kendal D; Pittman, Jon K

    2008-05-01

    Tonoplast-localised proton-coupled Ca(2+) transporters encoded by cation/H(+)exchanger (CAX) genes play a critical role in sequestering Ca(2+) into the vacuole. These transporters may function in coordination with Ca(2+) release channels, to shape stimulus-induced cytosolic Ca(2+) elevations. Recent analysis of Arabidopsis CAX knockout mutants, particularly cax1 and cax3, identified a variety of phenotypes including sensitivity to abiotic stresses, which indicated that these transporters might play a role in mediating the plant's stress response. A common feature of these mutants was the perturbation of H(+)-ATPase activity at both the tonoplast and the plasma membrane, suggesting a tight interplay between the Ca(2+)/H(+) exchangers and H(+) pumps. We speculate that indirect regulation of proton flux by the exchangers may be as important as the direct regulation of Ca(2+) flux. These results suggest cautious interpretation of mutant Ca(2+)/H(+) exchanger phenotypes that may be due to either perturbed Ca(2+) or H(+) transport.

  17. Self-calibrated correlation imaging with k-space variant correlation functions.

    Science.gov (United States)

    Li, Yu; Edalati, Masoud; Du, Xingfu; Wang, Hui; Cao, Jie J

    2018-03-01

    Correlation imaging is a previously developed high-speed MRI framework that converts parallel imaging reconstruction into the estimate of correlation functions. The presented work aims to demonstrate this framework can provide a speed gain over parallel imaging by estimating k-space variant correlation functions. Because of Fourier encoding with gradients, outer k-space data contain higher spatial-frequency image components arising primarily from tissue boundaries. As a result of tissue-boundary sparsity in the human anatomy, neighboring k-space data correlation varies from the central to the outer k-space. By estimating k-space variant correlation functions with an iterative self-calibration method, correlation imaging can benefit from neighboring k-space data correlation associated with both coil sensitivity encoding and tissue-boundary sparsity, thereby providing a speed gain over parallel imaging that relies only on coil sensitivity encoding. This new approach is investigated in brain imaging and free-breathing neonatal cardiac imaging. Correlation imaging performs better than existing parallel imaging techniques in simulated brain imaging acceleration experiments. The higher speed enables real-time data acquisition for neonatal cardiac imaging in which physiological motion is fast and non-periodic. With k-space variant correlation functions, correlation imaging gives a higher speed than parallel imaging and offers the potential to image physiological motion in real-time. Magn Reson Med 79:1483-1494, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  18. Hydrogen Exchange Mass Spectrometry of Functional Membrane-bound Chemotaxis Receptor Complexes

    Science.gov (United States)

    Koshy, Seena S.; Eyles, Stephen J.; Weis, Robert M.; Thompson, Lynmarie K.

    2014-01-01

    The transmembrane signaling mechanism of bacterial chemotaxis receptors is thought to involve changes in receptor conformation and dynamics. The receptors function in ternary complexes with two other proteins, CheA and CheW, that form extended membrane-bound arrays. Previous studies have shown that attractant binding induces a small (~2 Å) piston displacement of one helix of the periplasmic and transmembrane domains towards the cytoplasm, but it is not clear how this signal propagates through the cytoplasmic domain to control the kinase activity of the CheA bound at the membrane-distal tip, nearly 200 Å away. The cytoplasmic domain has been shown to be highly dynamic, which raises the question of how a small piston motion could propagate through a dynamic domain to control CheA kinase activity. To address this, we have developed a method for measuring dynamics of the receptor cytoplasmic fragment (CF) in functional complexes with CheA and CheW. Hydrogen exchange mass spectrometry (HDX-MS) measurements of global exchange of CF demonstrate that CF exhibits significantly slower exchange in functional complexes than in solution. Since the exchange rates in functional complexes are comparable to that of other proteins of similar structure, the CF appears to be a well-structured protein within these complexes, which is compatible with its role in propagating a signal that appears to be a tiny conformational change in the periplasmic and transmembrane domains of the receptor. We also demonstrate the feasibility of this protocol for local exchange measurements, by incorporating a pepsin digest step to produce peptides with 87% sequence coverage and only 20% back exchange. This method extends HDX-MS to membrane-bound functional complexes without detergents that may perturb the stability or structure of the system. PMID:24274333

  19. First evidence of intraclonal genetic exchange in trypanosomatids using two Leishmania infantum fluorescent transgenic clones.

    Directory of Open Access Journals (Sweden)

    Estefanía Calvo-Álvarez

    2014-09-01

    Full Text Available The mode of reproduction in Leishmania spp has been argued to be essentially clonal. However, recent data (genetic analysis of populations and co-infections in sand flies have proposed the existence of a non-obligate sexual cycle in the extracellular stage of the parasite within the sand fly vector. In this article we propose the existence of intraclonal genetic exchange in the natural vector of Leishmania infantum.We have developed transgenic L. infantum lines expressing drug resistance markers linked to green and red fluorescent reporters. We hypothesized whether those cells with identical genotype can recognize each other and mate. Both types of markers were successfully exchanged within the sand fly midgut of the natural vector Phlebotomus perniciosus when individuals from these species were fed with a mixture of parental clones. Using the yellow phenotype and drug resistance markers, we provide evidence for genetic exchange in L. infantum. The hybrid progeny appeared to be triploid based on DNA content analysis. The hybrid clone analyzed was stable throughout the complete parasite life cycle. The progress of infections by the hybrid clone in BALB/c mice caused a reduction in parasite loads in both spleen and liver, and provided weight values similar to those obtained with uninfected mice. Spleen arginase activity was also significantly reduced relative to parental strains.A L. infantum hybrid lineage was obtained from intraclonal genetic exchange within the midgut of the natural vector, suggesting the ability of this parasite to recognize the same genotype and mate. The yellow hybrid progeny is stable throughout the whole parasite life cycle but with a slower virulence, which correlates well with the lower arginase activity detected both in vitro and in vivo infections.

  20. Linker Flexibility Facilitates Module Exchange in Fungal Hybrid PKS-NRPS Engineering

    DEFF Research Database (Denmark)

    Nielsen, Maria Lund; Petersen, Thomas Isbrandt; Petersen, Lene Maj

    2016-01-01

    Polyketide synthases (PKSs) and nonribosomal peptide synthetases (NRPSs) each give rise to a vast array of complex bioactive molecules with further complexity added by the existence of natural PKS-NRPS fusions. Rational genetic engineering for the production of natural product derivatives....... We succeeded in the construction of a functional cross-species chimeric PKS-NRPS expressed in Aspergillus nidulans. Module swapping of the two PKS-NRPS natural hybrids CcsA from Aspergillus clavatus involved in the biosynthesis of cytochalasin E and related Syn2 from rice plant pathogen Magnaporthe...... oryzae lead to production of novel hybrid products, demonstrating that the rational re-design of these fungal natural product enzymes is feasible. We also report the structure of four novel pseudo pre-cytochalasin intermediates, niduclavin and niduporthin along with the chimeric compounds niduchimaeralin...

  1. Functional divergence caused by ancient positive selection of a Drosophila hybrid incompatibility locus.

    Directory of Open Access Journals (Sweden)

    Daniel A Barbash

    2004-06-01

    Full Text Available Interspecific hybrid lethality and sterility are a consequence of divergent evolution between species and serve to maintain the discrete identities of species. The evolution of hybrid incompatibilities has been described in widely accepted models by Dobzhansky and Muller where lineage-specific functional divergence is the essential characteristic of hybrid incompatibility genes. Experimentally tractable models are required to identify and test candidate hybrid incompatibility genes. Several Drosophila melanogaster genes involved in hybrid incompatibility have been identified but none has yet been shown to have functionally diverged in accordance with the Dobzhansky-Muller model. By introducing transgenic copies of the X-linked Hybrid male rescue (Hmr gene into D. melanogaster from its sibling species D. simulans and D. mauritiana, we demonstrate that Hmr has functionally diverged to cause F1 hybrid incompatibility between these species. Consistent with the Dobzhansky-Muller model, we find that Hmr has diverged extensively in the D. melanogaster lineage, but we also find extensive divergence in the sibling-species lineage. Together, these findings implicate over 13% of the amino acids encoded by Hmr as candidates for causing hybrid incompatibility. The exceptional level of divergence at Hmr cannot be explained by neutral processes because we use phylogenetic methods and population genetic analyses to show that the elevated amino-acid divergence in both lineages is due to positive selection in the distant past-at least one million generations ago. Our findings suggest that multiple substitutions driven by natural selection may be a general phenomenon required to generate hybrid incompatibility alleles.

  2. Enzymatic synthesis of lignin-siloxane hybrid functional polymers.

    Science.gov (United States)

    Prasetyo, Endry Nugroho; Kudanga, Tukayi; Fischer, Roman; Eichinger, Reinhard; Nyanhongo, Gibson S; Guebitz, Georg M

    2012-02-01

    This study combines the properties of siloxanes and lignin polymers to produce hybrid functional polymers that can be used as adhesives, coating materials, and/or multifunctionalized thin-coating films. Lignin-silica hybrid copolymers were synthesized by using a sol-gel process. Laccases from Trametes hirsuta were used to oxidize lignosulphonates to enhance their reactivity towards siloxanes and then were incorporated into siloxane precursors undergoing a sol-gel process. In vitro copolymerization studies using pure lignin monomers with aminosilanes or ethoxytrimethylsilane and analysis by ²⁹Si NMR spectroscopy revealed hybrid products. Except for kraft lignin, an increase in lignin concentration positively affected the tensile strength in all samples. Similarly, the viscosity generally increased in all samples with increasing lignin concentration and also affected the curing time. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Nonlocal exchange and kinetic-energy density functionals for electronic systems

    International Nuclear Information System (INIS)

    Glossman, M.D.; Rubio, A.; Balbas, L.C.; Alonso, J.A.

    1992-01-01

    The nonlocal weighted density approximation (WDA) to the exchange and kinetic-energy functionals of many electron systems proposed several years ago by Alonso and Girifalco is used to compute, within the framework of density functional theory, the ground-state electronic density and total energy of noble gas atoms and of neutral jellium-like sodium clusters containing up to 500 atoms. These results are compared with analogous calculations using the well known Thomas-Fermi-Weizsacker-Dirac (TFWD) approximations for the kinetic (TFW) and exchange (D) energy density functionals. An outstanding improvement of the total and exchange energies, of the density at the nucleus and of the expectation values is obtained for atoms within the WDA scheme. For sodium clusters the authors notice a sizeable contribution of the nonlocal effects to the total energy and to the density profiles. In the limit of very large clusters these effects should affect the surface energy of the bulk metal

  4. Major difference in visible-light photocatalytic features between perfect and self-defective Ta3N5 materials: A screened coulomb hybrid dft investigation

    KAUST Repository

    Harb, Moussab; Cavallo, Luigi; Basset, Jean-Marie

    2014-01-01

    theory (DFT, including the perturbation theory DFPT) within the screened coulomb hybrid (HSE06) exchange-correlation formalism. Among the various explored self-defective structures, a strong stabilization is obtained for the configuration displaying a

  5. Performance analysis of hybrid ground-coupled heat pump system with multi-functions

    International Nuclear Information System (INIS)

    You, Tian; Wang, Baolong; Wu, Wei; Shi, Wenxing; Li, Xianting

    2015-01-01

    Highlights: • The hybrid GCHP system with multi-functions is proposed. • The system maintains the soil temperature and heating reliability steady. • The multi-functional operation of HCUT can save more energy of the system. - Abstract: Underground thermal imbalance is a significant problem for ground-coupled heat pump (GCHP) systems that serve predominately heated buildings in cold regions, which extract more heat from the ground and inject less heat, especially in buildings requiring domestic hot water (DHW). To solve this problem, a previously developed heat compensation unit with thermosyphon (HCUT) is integrated with a GCHP unit to build a hybrid GCHP system. To improve the energy savings of this hybrid GCHP system, the HCUT unit is set to have multiple functions (heat compensation, direct DHW and direct space heating) in this paper. To analyze the improved system performance, a hotel requiring air-conditioning and DHW is selected and simulated in three typical cold cities using the dynamic software DeST and TRNSYS. The results indicate that the hybrid GCHP system can maintain the underground thermal balance while keeping the indoor air temperature within the design range. Furthermore, the HCUT unit efficiently reduces the energy consumption via its multi-functional operations. Compared to the previous system that only used HCUT for heat compensation, adding the direct DHW function further saves 7.5–11.0% energy in heat compensation (HC) and DHW (i.e., 3.6–4.8% of the whole system). Simultaneously adding the direct DHW and space heating functions to the HCUT can save 9.8–12.9% energy in HC and DHW (i.e., 5.1–6.0% of the whole system). The hybrid GCHP system with a multi-functional HCUT provides more energy savings while maintaining the underground thermal balance in cold regions that demand both air-conditioning and DHW

  6. Solution of the generalized Emden-Fowler equations by the hybrid functions method

    International Nuclear Information System (INIS)

    Tabrizidooz, H R; Marzban, H R; Razzaghi, M

    2009-01-01

    In this paper, we present a numerical algorithm for solving the generalized Emden-Fowler equations, which have many applications in mathematical physics and astrophysics. The method is based on hybrid functions approximations. The properties of hybrid functions, which consist of block-pulse functions and Lagrange interpolating polynomials, are presented. These properties are then utilized to reduce the computation of the generalized Emden-Fowler equations to a system of nonlinear equations. The method is easy to implement and yields very accurate results.

  7. Development and testing of new exchange correlation functionals

    DEFF Research Database (Denmark)

    Lundgård, Keld Troen

    , selectivity or similar of current chemical processes, or to make new technologies economical feasible. Kohn-Sham density functional theory (KS-DFT) has proven to be a powerful theory to find trends in current catalytic materials, which can empower a more informed search for better alternatives. KS-DFT relies...

  8. Synthesis and characterization of functional peek for ion-exchange membranes

    CSIR Research Space (South Africa)

    Luo, H

    2010-03-01

    Full Text Available The sulfonated and sulfinated polyetheretherketone (SsPEEK) was prepared via a novel method. SsPEEK has two types of functional groups, the functional groups for ion-exchange and the functional groups for further strengthening of the ion...

  9. Correlation Study of Magnetite Dissolution in Hybrid Decontamination Process

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seon-Byeong; Won, Hui-Jun; Park, Jung-Sun; Park, Sang-Yoon; Moon, Jei-Kwon; Choi, Wang-Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    In the operating plants, the localized corrosion on SG tubes which are transporters of thermal energy to the secondary side lowers the reduction heat transfer efficiency as well as degrades the lifetime of SG. Magnetite, Fe3O4, is a commonly found corrosion product on the inner surface of reactor coolant system. Simply magnetite can be reduced to hematite, Fe{sub 2}O{sub 3}, and further to iron when oxygen is limited or ample reducing agents are supplied. Along this line, number of decontamination processes has been developed since 1970s and most of them contain organic acid and additive chelating agents. However, many reports have pointed out the negative environmental effect of those chemicals, and currently there are new approaches to overcome the limited decontamination efficiency and large volume of secondary waste from other alternate processes without using such those organic chemicals. In present study, we investigated the magnetite dissolution in HyBRID solution as newly developing decontamination process. As a preliminary study for empirical modeling of decontamination by HyBRID solution, simply correlation study between variable and magnetite dissolution was introduced with studied mechanism and experimental results.

  10. Nuclear correlations and structure functions

    International Nuclear Information System (INIS)

    Hu Guoju; Irvine, J.M.

    1989-01-01

    It is argued that the search for a mass number dependence of the nuclear structure function per nucleon is profitably directed to the region of Bjorken scaling variable x > 1. We show that in the convolution model of the nuclear structure function the nuclear momentum distribution and energy spectrum generated by cluster expansion techniques, here realised in the correlated basis function method, invoking tensor correlations and short-range density-dependent repulsions adequately describes the structure function for 12 C in the region x > 1. The results of structure functions for a number of light-, medium- and heavy-mass nuclei are presented. (author)

  11. Multicomponent density functional theory embedding formulation

    Energy Technology Data Exchange (ETDEWEB)

    Culpitt, Tanner; Brorsen, Kurt R.; Pak, Michael V.; Hammes-Schiffer, Sharon, E-mail: shs3@illinois.edu [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Ave, Urbana, Illinois 61801 (United States)

    2016-07-28

    Multicomponent density functional theory (DFT) methods have been developed to treat two types of particles, such as electrons and nuclei, quantum mechanically at the same level. In the nuclear-electronic orbital (NEO) approach, all electrons and select nuclei, typically key protons, are treated quantum mechanically. For multicomponent DFT methods developed within the NEO framework, electron-proton correlation functionals based on explicitly correlated wavefunctions have been designed and used in conjunction with well-established electronic exchange-correlation functionals. Herein a general theory for multicomponent embedded DFT is developed to enable the accurate treatment of larger systems. In the general theory, the total electronic density is separated into two subsystem densities, denoted as regular and special, and different electron-proton correlation functionals are used for these two electronic densities. In the specific implementation, the special electron density is defined in terms of spatially localized Kohn-Sham electronic orbitals, and electron-proton correlation is included only for the special electron density. The electron-proton correlation functional depends on only the special electron density and the proton density, whereas the electronic exchange-correlation functional depends on the total electronic density. This scheme includes the essential electron-proton correlation, which is a relatively local effect, as well as the electronic exchange-correlation for the entire system. This multicomponent DFT-in-DFT embedding theory is applied to the HCN and FHF{sup −} molecules in conjunction with two different electron-proton correlation functionals and three different electronic exchange-correlation functionals. The results illustrate that this approach provides qualitatively accurate nuclear densities in a computationally tractable manner. The general theory is also easily extended to other types of partitioning schemes for multicomponent systems.

  12. Significance and properties of internucleon correlation functions

    OpenAIRE

    Suzuki, Y.; Horiuchi, W.

    2008-01-01

    We show that a nuclear Hamiltonian and a set of internucleon correlation functions is in a one-to-one correspondence. The correlation functions for $s$-shell nuclei interacting via the two-nucleon interaction of AV8$^\\prime$ type are calculated to exhibit the importance of tensor correlations as well as short-range central correlation. The asymptotic behavior of the correlation functions is also discussed.

  13. Optical data exchange of m-QAM signals using a silicon-organic hybrid slot waveguide: proposal and simulation.

    Science.gov (United States)

    Gui, Chengcheng; Wang, Jian

    2014-10-06

    We present modulation-format-transparent data exchange for m-ary quadrature amplitude modulation (m-QAM) signals using a single silicon-organic hybrid slot waveguide which offers tight light confinement and enhanced nonlinearity. By exploiting the parametric depletion effect of non-degenerate four-wave mixing (ND-FWM) process in the slot waveguide, we simulate low-power (exchange of 640 Gbaud (2.56 Tbit/s) optical time-division multiplexed (OTDM) 16-QAM and 640 Gbaud (3.84 Tbit/s) OTDM 64-QAM signals and characterize the operation performance in terms of error vector magnitude (EVM) and bit-error rate (BER). The calculated signal-to-noise ratio (SNR) penalties of data exchange are negligible for 2.56 Tbit/s 16-QAM signals and less than 2 dB for 3.84 Tbit/s 64-QAM signals at a BER of 2e-3. For a given pump power of 9 mW, the operation performance dependence on the waveguide length is studied, showing an optimized waveguide length of ~17 mm. For a given waveguide length of 17 mm, the SNR penalty of data exchange, at a BER of 2e-3, is kept below 4 dB when varying input pump power from 8.4 to 9.8 mW for 2.56 Tbit/s 16-QAM and from 8.9 to 9.2 mW for 3.84 Tbit/s 64-QAM. In addition, data exchange running at low speed (e.g. 20 Gbaud) and data exchange taking into account waveguide propagation loss are also analyzed with favorable operation performance.

  14. Impact of exchange-correlation effects on the IV characteristics of a molecular junction

    DEFF Research Database (Denmark)

    Thygesen, Kristian Sommer

    2008-01-01

    The role of exchange-correlation effects in nonequilibrium quantum transport through molecular junctions is assessed by analyzing the IV curve of a generic two-level model using self-consistent many-body perturbation theory (second Born and GW approximations) on the Keldysh contour. It is demonst...... of dynamic correlations introduces quasiparticle (QP) scattering which in turn broadens the molecular resonances. The broadening increases strongly with bias and can have a large impact on the calculated IV characteristic....

  15. Intelligent Soft Computing on Forex: Exchange Rates Forecasting with Hybrid Radial Basis Neural Network.

    Science.gov (United States)

    Falat, Lukas; Marcek, Dusan; Durisova, Maria

    2016-01-01

    This paper deals with application of quantitative soft computing prediction models into financial area as reliable and accurate prediction models can be very helpful in management decision-making process. The authors suggest a new hybrid neural network which is a combination of the standard RBF neural network, a genetic algorithm, and a moving average. The moving average is supposed to enhance the outputs of the network using the error part of the original neural network. Authors test the suggested model on high-frequency time series data of USD/CAD and examine the ability to forecast exchange rate values for the horizon of one day. To determine the forecasting efficiency, they perform a comparative statistical out-of-sample analysis of the tested model with autoregressive models and the standard neural network. They also incorporate genetic algorithm as an optimizing technique for adapting parameters of ANN which is then compared with standard backpropagation and backpropagation combined with K-means clustering algorithm. Finally, the authors find out that their suggested hybrid neural network is able to produce more accurate forecasts than the standard models and can be helpful in eliminating the risk of making the bad decision in decision-making process.

  16. Exchange–correlation errors at harmonic and anharmonic orders

    Indian Academy of Sciences (India)

    As an aid towards improving the treatment of exchange and correlation effects in electronic structure calculations, it is desirable to have a clear picture of the errors introduced by currently popular approximate exchange–correlation functionals. We have performed ab initio density functional theory and density functional ...

  17. Lung scan abnormalities in asthma and their correlation with lung function

    International Nuclear Information System (INIS)

    Vernon, P.; Burton, G.H.; Seed, W.A.; Charing Cross Hospital, London

    1986-01-01

    We have used asthma as a model of airways disease to test how well an automated, quantitative method of analysis of lung scans correlates with physiological measurements of disturbed lung function and gas exchange. We studies 25 asthmatics (age 16-73) of widely differing severity (forced expiratory volume in 1-s FEV 1 22%-123% of predicted value), who had airways tests, arterial blood gas analysis, and krypton-technetium lung scans within a short time of each other. In all patients with airways obstruction and in some with normal function during remission, scans showed the typical appearances of multiple defects of ventilation and perfusion. The severity of ventilation defects was assessed from the posterior view of the krypton scan compared to an age- and sex-matched normal range to yield an underventilation score. This correlated closely with the severity of airways obstruction as measured by forced expiratory manouevres. Ventilation and perfusion defects were usually imperfectly matched; the severity of this was computed using a subtraction method applied to the counts on the posterior krypton and technetium scans. The degree of mismatch was inversely related to the arterial partial pressure of oxygen (r=-0.86). The results suggest that computer scan analysis can provide usual functional information about the lung in airways disease. (orig.)

  18. Amine-functionalized, silver-exchanged zeolite NaY: Preparation, characterization and antibacterial activity

    Energy Technology Data Exchange (ETDEWEB)

    Hanim, Siti Aishah Mohd; Malek, Nik Ahmad Nizam Nik, E-mail: niknizam@fbb.utm.my; Ibrahim, Zaharah

    2016-01-01

    Graphical abstract: - Highlights: • Functionalization of Ag-exchanged zeolite NaY with 3-aminopropyltriethoxysilane APTES (ZSA) as antibacterial agent. • Antibacterial assay of ZSA was performed against Escherichia coli ATCC11229 and Staphylococcus aureus ATCC6538. • Functionalization of Ag-exchanged zeolite NaY with APTES significantly increased the antibacterial agent. • Different mechanisms of bacterial death were suggested for each bacteria type by the functionalized Ag-exchanged zeolite NaY. - Abstract: Amine-functionalized, silver-exchanged zeolite NaY (ZSA) were prepared with three different concentrations of 3-aminopropyltriethoxysilane (APTES) (0.01, 0.20 and 0.40 M) and four different concentrations of silver ions (25%, 50%, 100% and 200% from zeolite cation exchange capacity (CEC)). The samples were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX), surface area analysis, thermogravimetric analysis (TGA) and zeta potential (ZP) analysis. The FTIR results indicated that the zeolite was functionalized by APTES and that the intensity of the peaks corresponding to APTES increased as the concentration of APTES used was increased. The antibacterial activities of the silver-exchanged zeolite NaY (ZS) and ZSA were studied against Escherichia coli ATCC11229 and Staphylococcus aureus ATCC6538 using the disc diffusion technique (DDT) and minimum inhibitory concentration (MIC). The antibacterial activity of ZSA increased with the increase in APTES on ZS, and E. coli was more susceptible towards the sample compared to S. aureus. The FESEM micrographs of the bacteria after contact with the ZSA suggested different mechanisms of bacterial death for these two bacteria due to exposure to the studied sample. The functionalization of ZS with APTES improved the antibacterial activity of the silver-zeolite, depending on the concentration of silver

  19. Synthesis, characterization and analytical application of hybrid; Acrylamide zirconium (IV) arsenate a cation exchanger, effect of dielectric constant on distribution coefficient of metal ions

    Energy Technology Data Exchange (ETDEWEB)

    Nabi, Syed A. [Department of Chemistry, Aligarh Muslim University, Aligarh 202002, U.P. (India)], E-mail: sanabi@rediffmail.com; Shalla, Aabid H. [Department of Chemistry, Aligarh Muslim University, Aligarh 202002, U.P. (India)

    2009-04-30

    A new hybrid inorganic-organic cation exchanger acrylamide zirconium (IV) arsenate has been synthesized, characterized and its analytical application explored. The effect of experimental parameters such as mixing ratio of reagents, temperature, and pH on the properties of material has been studied. FTIR, TGA, X-ray, UV-vis spectrophotometry, SEM and elemental analysis were used to determine the physiochemical properties of this hybrid ion exchanger. The material behaves as a monofunctional acid with ion-exchange capacity of 1.65 meq/g for Na{sup +} ions. The chemical stability data reveals that the exchanger is quite stable in mineral acids, bases and fairly stable in organic solvents, while as thermal analysis shows that the material retain 84% of its ion-exchange capacity up to 600 deg. C. Adsorption behavior of metal ions in solvents with increasing dielectric constant has also been explored. The sorption studies reveal that the material is selective for Pb{sup 2+} ions. The analytical utility of the material has been explored by achieving some binary separations of metal ions on its column. Pb{sup 2+} has been selectively removed from synthetic mixtures containing Mg{sup 2+}, Ca{sup 2+}, Sr{sup 2+}, Zn{sup 2+} and Cu{sup 2+}, Al{sup 3+}, Ni{sup 2+}, Fe{sup 3+}. In order to demonstrate practical utility of the material quantitative separation of the Cu{sup 2+} and Zn{sup 2+} in brass sample has been achieved on its columns.

  20. Xylem anatomy correlates with gas exchange, water-use efficiency and growth performance under contrasting water regimes: evidence from Populus deltoides x Populus nigra hybrids.

    Science.gov (United States)

    Fichot, Régis; Laurans, Françoise; Monclus, Romain; Moreau, Alain; Pilate, Gilles; Brignolas, Franck

    2009-12-01

    Six Populus deltoides Bartr. ex Marsh. x P. nigra L. genotypes were selected to investigate whether stem xylem anatomy correlated with gas exchange rates, water-use efficiency (WUE) and growth performance. Clonal copies of the genotypes were grown in a two-plot common garden test under contrasting water regimes, with one plot maintained irrigated and the other one subjected to moderate summer water deficit. The six genotypes displayed a large range of xylem anatomy, mean vessel and fibre diameter varying from about 40 to 60 microm and from 7.5 to 10.5 microm, respectively. Decreased water availability resulted in a reduced cell size and an important rise in vessel density, but the extent of xylem plasticity was both genotype and trait dependent. Vessel diameter and theoretical xylem-specific hydraulic conductivity correlated positively with stomatal conductance, carbon isotope discrimination and growth performance-related traits and negatively with intrinsic WUE, especially under water deficit conditions. Vessel diameter and vessel density measured under water deficit conditions correlated with the relative losses in biomass production in response to water deprivation; this resulted from the fact that a more plastic xylem structure was generally accompanied by a larger loss in biomass production.

  1. Benchmarking singlet and triplet excitation energies of molecular semiconductors for singlet fission: Tuning the amount of HF exchange and adjusting local correlation to obtain accurate functionals for singlet-triplet gaps

    Science.gov (United States)

    Brückner, Charlotte; Engels, Bernd

    2017-01-01

    Vertical and adiabatic singlet and triplet excitation energies of molecular p-type semiconductors calculated with various DFT functionals and wave-function based approaches are benchmarked against MS-CASPT2/cc-pVTZ reference values. A special focus lies on the singlet-triplet gaps that are very important in the process of singlet fission. Singlet fission has the potential to boost device efficiencies of organic solar cells, but the scope of existing singlet-fission compounds is still limited. A computational prescreening of candidate molecules could enlarge it; yet it requires efficient methods accurately predicting singlet and triplet excitation energies. Different DFT formulations (Tamm-Dancoff approximation, linear response time-dependent DFT, Δ-SCF) and spin scaling schemes along with several ab initio methods (CC2, ADC(2)/MP2, CIS(D), CIS) are evaluated. While wave-function based methods yield rather reliable singlet-triplet gaps, many DFT functionals are shown to systematically underestimate triplet excitation energies. To gain insight, the impact of exact exchange and correlation is in detail addressed.

  2. Electroweak production of hybrid mesons in a flux-tube simulation of lattice QCD

    International Nuclear Information System (INIS)

    Close, F.E.; Dudek, J.J.

    2003-01-01

    We make the first calculation of the electroweak couplings of hybrid mesons to conventional mesons appropriate to photoproduction and to the decays of B or D mesons. E1 amplitudes are found to be large and may contribute in charge exchange γp→nH + allowing production of (among others) the charged 1 -+ exotic hybrid off a 2 exchange. Axial hybrid meson photoproduction is predicted to be large courtesy of π exchange, and its strange hybrid counterpart is predicted in B→ψK H (1 + ) with branching ratio B∼10 -4 . Higher multipoles and some implications for hybrid charmonium are briefly discussed

  3. Unravelling the tunable exchange bias-like effect in magnetostatically-coupled two dimensional hybrid (hard/soft) composites

    International Nuclear Information System (INIS)

    Hierro-Rodriguez, A; Teixeira, J M; Rodriguez-Rodriguez, G; Rubio, H; Vélez, M; Álvarez-Prado, L M; Martín, J I; Alameda, J M

    2015-01-01

    Hybrid 2D hard-soft composites have been fabricated by combining soft (Co 73 Si 27 ) and hard (NdCo 5 ) magnetic materials with in-plane and out-of-plane magnetic anisotropies, respectively. They have been microstructured in a square lattice of CoSi anti-dots with NdCo dots within the holes. The magnetic properties of the dots allow us to introduce a magnetostatic stray field that can be controlled in direction and sense by their last saturating magnetic field. The magnetostatic interactions between dot and anti-dot layers induce a completely tunable exchange bias-like shift in the system’s hysteresis loops. Two different regimes for this shift are present depending on the lattice parameter of the microstructures. For large parameters, dipolar magnetostatic decay is observed, while for the smaller one, the interaction between the adjacent anti-dot’s characteristic closure domain structures enhances the exchange bias-like effect as clarified by micromagnetic simulations. (paper)

  4. Accurate and systematically improvable density functional theory embedding for correlated wavefunctions

    International Nuclear Information System (INIS)

    Goodpaster, Jason D.; Barnes, Taylor A.; Miller, Thomas F.; Manby, Frederick R.

    2014-01-01

    We analyze the sources of error in quantum embedding calculations in which an active subsystem is treated using wavefunction methods, and the remainder using density functional theory. We show that the embedding potential felt by the electrons in the active subsystem makes only a small contribution to the error of the method, whereas the error in the nonadditive exchange-correlation energy dominates. We test an MP2 correction for this term and demonstrate that the corrected embedding scheme accurately reproduces wavefunction calculations for a series of chemical reactions. Our projector-based embedding method uses localized occupied orbitals to partition the system; as with other local correlation methods, abrupt changes in the character of the localized orbitals along a reaction coordinate can lead to discontinuities in the embedded energy, but we show that these discontinuities are small and can be systematically reduced by increasing the size of the active region. Convergence of reaction energies with respect to the size of the active subsystem is shown to be rapid for all cases where the density functional treatment is able to capture the polarization of the environment, even in conjugated systems, and even when the partition cuts across a double bond

  5. Functionalized graphene oxide/Fe3O4 hybrids for cellular magnetic resonance imaging and fluorescence labeling.

    Science.gov (United States)

    Zhou, Chaohui; Wu, Hui; Wang, Mingliang; Huang, Chusen; Yang, Dapeng; Jia, Nengqin

    2017-09-01

    In this work, we developed a T 2 -weighted contrast agent based on graphene oxide (GO)/Fe 3 O 4 hybrids for efficient cellular magnetic resonance imaging (MRI). The GO/Fe 3 O 4 hybrids were obtained by combining with co-precipitation method and pyrolysis method. The structural, surface and magnetic characteristics of the hybrids were systematically characterized by transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), AFM, Raman, FT-IR and XRD. The GO/Fe 3 O 4 hybrids were functionalized by modifying with anionic and cationic polyelectrolyte through layer-by-layer assembling. The fluorescence probe fluorescein isothiocyanate (FITC) was further loaded on the surface of functionalized GO/Fe 3 O 4 hybrids to trace the location of GO/Fe 3 O 4 hybrids in cells. Functionalized GO/Fe 3 O 4 hybrids possess good hydrophilicity, less cytotoxicity, high MRI enhancement with the relaxivity (r 2 ) of 493mM -1 s -1 as well as cellular MRI contrast effect. These obtained results indicated that the functionalized GO/Fe 3 O 4 hybrids could have great potential to be utilized as cellular MRI contrast agents for tumor early diagnosis and monitoring. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Structuring Stokes correlation functions using vector-vortex beam

    Science.gov (United States)

    Kumar, Vijay; Anwar, Ali; Singh, R. P.

    2018-01-01

    Higher order statistical correlations of the optical vector speckle field, formed due to scattering of a vector-vortex beam, are explored. Here, we report on the experimental construction of the Stokes parameters covariance matrix, consisting of all possible spatial Stokes parameters correlation functions. We also propose and experimentally realize a new Stokes correlation functions called Stokes field auto correlation functions. It is observed that the Stokes correlation functions of the vector-vortex beam will be reflected in the respective Stokes correlation functions of the corresponding vector speckle field. The major advantage of proposing Stokes correlation functions is that the Stokes correlation function can be easily tuned by manipulating the polarization of vector-vortex beam used to generate vector speckle field and to get the phase information directly from the intensity measurements. Moreover, this approach leads to a complete experimental Stokes characterization of a broad range of random fields.

  7. Gas exchange and leaf anatomy of a C3-CAM hybrid, Yucca gloriosa (Asparagaceae).

    Science.gov (United States)

    Heyduk, Karolina; Burrell, Nia; Lalani, Falak; Leebens-Mack, Jim

    2016-03-01

    While the majority of plants use the typical C3 carbon metabolic pathway, ~6% of angiosperms have adapted to carbon limitation as a result of water stress by employing a modified form of photosynthesis known as Crassulacean acid metabolism (CAM). CAM plants concentrate carbon in the cells by temporally separating atmospheric carbon acquisition from fixation into carbohydrates. CAM has been studied for decades, but the evolutionary progression from C3 to CAM remains obscure. In order to better understand the morphological and physiological characteristics associated with CAM photosynthesis, phenotypic variation was assessed in Yucca aloifolia, a CAM species, Yucca filamentosa, a C3 species, and Yucca gloriosa, a hybrid species derived from these two yuccas exhibiting intermediate C3-CAM characteristics. Gas exchange, titratable leaf acidity, and leaf anatomical traits of all three species were assayed in a common garden under well-watered and drought-stressed conditions. Yucca gloriosa showed intermediate phenotypes for nearly all traits measured, including the ability to acquire carbon at night. Using the variation found among individuals of all three species, correlations between traits were assessed to better understand how leaf anatomy and CAM physiology are related. Yucca gloriosa may be constrained by a number of traits which prevent it from using CAM to as high a degree as Y. aloifolia. The intermediate nature of Y. gloriosa makes it a promising system in which to study the evolution of CAM. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  8. Effects of side-chain and electron exchange correlation on the band structure of perylene diimide liquid crystals: a density functional study.

    Science.gov (United States)

    Arantes, J T; Lima, M P; Fazzio, A; Xiang, H; Wei, Su-Huai; Dalpian, G M

    2009-04-23

    The structural and electronic properties of perylene diimide liquid crystal PPEEB are studied using ab initio methods based on the density functional theory (DFT). Using available experimental crystallographic data as a guide, we propose a detailed structural model for the packing of solid PPEEB. We find that due to the localized nature of the band edge wave function, theoretical approaches beyond the standard method, such as hybrid functional (PBE0), are required to correctly characterize the band structure of this material. Moreover, unlike previous assumptions, we observe the formation of hydrogen bonds between the side chains of different molecules, which leads to a dispersion of the energy levels. This result indicates that the side chains of the molecular crystal not only are responsible for its structural conformation but also can be used for tuning the electronic and optical properties of these materials.

  9. Two-proton correlation function: a gentle introduction

    International Nuclear Information System (INIS)

    Deloff, A.

    2007-01-01

    The recent COSY-11 collaboration measurement of the two-proton correlation function in the pp→ppη reaction, reported at this meeting [1], arouse some interest in a simple theoretical description of the correlation function. In these notes we present a pedagogical introduction to the practical methods that can be used for calculating the correlation function

  10. Brain PET and functional MRI: why simultaneously using hybrid PET/MR systems?

    Science.gov (United States)

    Cecchin, Diego; Palombit, Alessandro; Castellaro, Marco; Silvestri, Erica; Bui, Franco; Barthel, Henryk; Sabri, Osama; Corbetta, Maurizio; Bertoldo, Alessandra

    2017-12-01

    In the last 20 years growing attention has been devoted to multimodal imaging. The recent literature is rich of clinical and research studies that have been performed using different imaging modalities on both separate and integrated positron emission tomography (PET) and magnetic resonance (MR) scanners. However, today, hybrid PET/MR systems measure signals related to brain structure, metabolism, neurochemistry, perfusion, and neuronal activity simultaneously, i.e. in the same physiological conditions. A frequently raised question at meeting and symposia is: "Do we really need a hybrid PET/MR system? Are there any advantages over acquiring sequential and separate PET and MR scans?" The present paper is an attempt to answer these questions specifically in relation to PET combined with functional magnetic resonance imaging (fMRI) and arterial spin labeling. We searched (last update: June 2017) the databases PubMed, PMC, Google Scholar and Medline. We also included additional studies if they were cited in the selected articles. No language restriction was applied to the search, but the reviewed articles were all in English. Among all the retrieved articles, we selected only those performed using a hybrid PET/MR system. We found a total of 17 papers that were selected and discussed in three main groups according to the main radiopharmaceutical used: 18F-fluorodeoxyglucose (18F-FDG) (N.=8), 15O-water (15O-H2O) (N.=3) and neuroreceptors (N.=6). Concerning studies using 18F-FDG, simultaneous PET/fMRI revealed that global aspects of functional organization (e.g. graph properties of functional connections) are partially associated with energy consumption. There are remarkable spatial and functional similarities across modalities, but also discrepant findings. More work is needed on this point. There are only a handful of papers comparing blood flow measurements with PET 15O-H2O and MR arterial spin label (ASL) measures, and they show significant regional CBF differences

  11. Correlation functions of Coulomb branch operators

    Energy Technology Data Exchange (ETDEWEB)

    Gerchkovitz, Efrat [Weizmann Institute of Science,Rehovot 76100 (Israel); Gomis, Jaume [Perimeter Institute for Theoretical Physics,Waterloo, ON N2L 2Y5 (Canada); Ishtiaque, Nafiz [Perimeter Institute for Theoretical Physics,Waterloo, ON N2L 2Y5 (Canada); Department of Physics, University of Waterloo,Waterloo, ON N2L 3G1 (Canada); Karasik, Avner; Komargodski, Zohar [Weizmann Institute of Science,Rehovot 76100 (Israel); Pufu, Silviu S. [Joseph Henry Laboratories, Princeton University,Princeton, NJ 08544 (United States)

    2017-01-24

    We consider the correlation functions of Coulomb branch operators in four-dimensional N=2 Superconformal Field Theories (SCFTs) involving exactly one anti-chiral operator. These extremal correlators are the “minimal' non-holomorphic local observables in the theory. We show that they can be expressed in terms of certain determinants of derivatives of the four-sphere partition function of an appropriate deformation of the SCFT. This relation between the extremal correlators and the deformed four-sphere partition function is non-trivial due to the presence of conformal anomalies, which lead to operator mixing on the sphere. Evaluating the deformed four-sphere partition function using supersymmetric localization, we compute the extremal correlators explicitly in many interesting examples. Additionally, the representation of the extremal correlators mentioned above leads to a system of integrable differential equations. We compare our exact results with previous perturbative computations and with the four-dimensional tt{sup ∗} equations. We also use our results to study some of the asymptotic properties of the perturbative series expansions we obtain in N=2 SQCD.

  12. Fast Response, Load-Matching Hybrid Fuel Cell: Final Technical Progress Report

    Energy Technology Data Exchange (ETDEWEB)

    Key, T. S.; Sitzlar, H. E.; Geist, T. D.

    2003-06-01

    Hybrid DER technologies interconnected with the grid can provide improved performance capabilities compared to a single power source, and, add value, when matched to appropriate applications. For example, in a typical residence, the interconnected hybrid system could provide power during a utility outage, and also could compensate for voltage sags in the utility service. Such a hybrid system would then function as a premium power provider and eliminate the potential need for an uninterruptible power supply. In this research project, a proton exchange membrane (PEM) fuel cell is combined with an asymmetrical ultracapacitor to provide robust power response to changes in system loading. This project also considers the potential of hybrid DER technologies to improve overall power system compatibility and performance. This report includes base year accomplishments of a proposed 3-year-option project.

  13. Short-range correlations with pseudopotentials

    International Nuclear Information System (INIS)

    Osman, A.

    1976-01-01

    Short-range correlations in nuclei are considered on an unitary-model operator approach. Short-range pseudopotentials have been added to achieve healing in the correlated wave functions. With the introduction of the pseudopotentials, correlated basis wave functions are constructed. The matrix element for effective interaction in nuclei is developed. The required pseudopotentials have been calculated for the Hamda-Johnston, Yale and Reid potentials and for the nuclear nucleon-nucleon potential A calculated by us according to meson exchange between nucleons. (Osman, A.)

  14. Intelligent Soft Computing on Forex: Exchange Rates Forecasting with Hybrid Radial Basis Neural Network

    Directory of Open Access Journals (Sweden)

    Lukas Falat

    2016-01-01

    Full Text Available This paper deals with application of quantitative soft computing prediction models into financial area as reliable and accurate prediction models can be very helpful in management decision-making process. The authors suggest a new hybrid neural network which is a combination of the standard RBF neural network, a genetic algorithm, and a moving average. The moving average is supposed to enhance the outputs of the network using the error part of the original neural network. Authors test the suggested model on high-frequency time series data of USD/CAD and examine the ability to forecast exchange rate values for the horizon of one day. To determine the forecasting efficiency, they perform a comparative statistical out-of-sample analysis of the tested model with autoregressive models and the standard neural network. They also incorporate genetic algorithm as an optimizing technique for adapting parameters of ANN which is then compared with standard backpropagation and backpropagation combined with K-means clustering algorithm. Finally, the authors find out that their suggested hybrid neural network is able to produce more accurate forecasts than the standard models and can be helpful in eliminating the risk of making the bad decision in decision-making process.

  15. Intelligent Soft Computing on Forex: Exchange Rates Forecasting with Hybrid Radial Basis Neural Network

    Science.gov (United States)

    Marcek, Dusan; Durisova, Maria

    2016-01-01

    This paper deals with application of quantitative soft computing prediction models into financial area as reliable and accurate prediction models can be very helpful in management decision-making process. The authors suggest a new hybrid neural network which is a combination of the standard RBF neural network, a genetic algorithm, and a moving average. The moving average is supposed to enhance the outputs of the network using the error part of the original neural network. Authors test the suggested model on high-frequency time series data of USD/CAD and examine the ability to forecast exchange rate values for the horizon of one day. To determine the forecasting efficiency, they perform a comparative statistical out-of-sample analysis of the tested model with autoregressive models and the standard neural network. They also incorporate genetic algorithm as an optimizing technique for adapting parameters of ANN which is then compared with standard backpropagation and backpropagation combined with K-means clustering algorithm. Finally, the authors find out that their suggested hybrid neural network is able to produce more accurate forecasts than the standard models and can be helpful in eliminating the risk of making the bad decision in decision-making process. PMID:26977450

  16. Skin-inspired hydrogel-elastomer hybrids with robust interfaces and functional microstructures

    Science.gov (United States)

    Yuk, Hyunwoo; Zhang, Teng; Parada, German Alberto; Liu, Xinyue; Zhao, Xuanhe

    2016-06-01

    Inspired by mammalian skins, soft hybrids integrating the merits of elastomers and hydrogels have potential applications in diverse areas including stretchable and bio-integrated electronics, microfluidics, tissue engineering, soft robotics and biomedical devices. However, existing hydrogel-elastomer hybrids have limitations such as weak interfacial bonding, low robustness and difficulties in patterning microstructures. Here, we report a simple yet versatile method to assemble hydrogels and elastomers into hybrids with extremely robust interfaces (interfacial toughness over 1,000 Jm-2) and functional microstructures such as microfluidic channels and electrical circuits. The proposed method is generally applicable to various types of tough hydrogels and diverse commonly used elastomers including polydimethylsiloxane Sylgard 184, polyurethane, latex, VHB and Ecoflex. We further demonstrate applications enabled by the robust and microstructured hydrogel-elastomer hybrids including anti-dehydration hydrogel-elastomer hybrids, stretchable and reactive hydrogel-elastomer microfluidics, and stretchable hydrogel circuit boards patterned on elastomer.

  17. Multiconfiguration Pair-Density Functional Theory Outperforms Kohn-Sham Density Functional Theory and Multireference Perturbation Theory for Ground-State and Excited-State Charge Transfer.

    Science.gov (United States)

    Ghosh, Soumen; Sonnenberger, Andrew L; Hoyer, Chad E; Truhlar, Donald G; Gagliardi, Laura

    2015-08-11

    The correct description of charge transfer in ground and excited states is very important for molecular interactions, photochemistry, electrochemistry, and charge transport, but it is very challenging for Kohn-Sham (KS) density functional theory (DFT). KS-DFT exchange-correlation functionals without nonlocal exchange fail to describe both ground- and excited-state charge transfer properly. We have recently proposed a theory called multiconfiguration pair-density functional theory (MC-PDFT), which is based on a combination of multiconfiguration wave function theory with a new type of density functional called an on-top density functional. Here we have used MC-PDFT to study challenging ground- and excited-state charge-transfer processes by using on-top density functionals obtained by translating KS exchange-correlation functionals. For ground-state charge transfer, MC-PDFT performs better than either the PBE exchange-correlation functional or CASPT2 wave function theory. For excited-state charge transfer, MC-PDFT (unlike KS-DFT) shows qualitatively correct behavior at long-range with great improvement in predicted excitation energies.

  18. Perturbed angular correlation study of the ion exchange of indium into silicalite zeolites

    International Nuclear Information System (INIS)

    Ramallo-Lopez, J.M.; Requejo, F.G.; Renteria, M.; Bibiloni, A.G.; Miro, E.E.

    1999-01-01

    Two indium-containing silicalite zeolites (In/H-ZSM5) catalysts prepared by wet impregnation and ionic exchange were characterized by the Perturbed Angular Correlation (PAC) technique using 111 In as probe to determine the nature of the indium species. Some of these species take part in the catalytic reaction of the selective reduction (SCR) of NO x with methane. PAC experiments were performed at 500 deg. C in air before and after reduction-reoxidation treatments on the catalysts in order to determine the origin of the different hyperfine interactions and then the degree of ionic exchange. Complementary catalytic activity characterizations were also performed.PAC experiments performed on the catalyst obtained by wet impregnation showed that all In-atoms form In 2 O 3 crystallites while almost 70% of In-atoms form In 2 O 3 in the catalyst obtained by ionic exchange. The PAC experiments of both catalysts performed after the reduction-reoxidation treatment revealed the presence of two hyperfine interactions, different from those corresponding to indium in In 2 O 3 . These hyperfine interactions should be associated to disperse In species responsible of the catalytic activity located in the ionic exchange-sites of the zeolites

  19. The nature of excess electrons in anatase and rutile from hybrid DFT and RPA.

    Science.gov (United States)

    Spreafico, Clelia; VandeVondele, Joost

    2014-12-21

    The behavior of excess electrons in undoped and defect free bulk anatase and rutile TiO2 has been investigated by state-of-the-art electronic structure methods including hybrid density functional theory (DFT) and the random phase approximation (RPA). Consistent with experiment, charge trapping and polaron formation is observed in both anatase and rutile. The difference in the anisotropic shape of the polarons is characterized, confirming for anatase the large polaron picture. For anatase, where polaron formation energies are small, charge trapping is observed also with standard hybrid functionals, provided the simulation cell is sufficiently large (864 atoms) to accommodate the lattice relaxation. Even though hybrid orbitals are required as a starting point for RPA in this system, the obtained polaron formation energies are relatively insensitive to the amount of Hartree-Fock exchange employed. The difference in trapping energy between rutile and anatase can be obtained accurately with both hybrid functionals and RPA. Computed activation energies for polaron hopping and delocalization clearly show that anatase and rutile might have different charge transport mechanisms. In rutile, only hopping is likely, whereas in anatase hopping and delocalization are competing. Delocalization will result in conduction-band-like and thus enhanced transport. Anisotropic conduction, in agreement with experimental data, is observed, and results from the tendency to delocalize in the [001] direction in rutile and the (001) plane in anatase. For future work, our calculations serve as a benchmark and suggest RPA on top on hybrid orbitals (PBE0 with 30% Hartree-Fock exchange), as a suitable method to study the rich chemistry and physics of TiO2.

  20. A pair density functional theory utilizing the correlated wave function

    International Nuclear Information System (INIS)

    Higuchi, M; Higuchi, K

    2009-01-01

    We propose a practical scheme for calculating the ground-state pair density (PD) by utilizing the correlated wave function. As the correlated wave function, we adopt a linear combination of the single Slater determinants that are constructed from the solutions of the initial scheme [Higuchi M and Higuchi K 2007 Physica B 387, 117]. The single-particle equation is derived by performing the variational principle within the set of PDs that are constructed from such correlated wave functions. Since the search region of the PD is substantially extended as compared with the initial scheme, it is expected that the present scheme can cover more correlation effects. The single-particle equation is practical, and may be easily applied to actual calculations.

  1. Integral equations of hadronic correlation functions a functional- bootstrap approach

    CERN Document Server

    Manesis, E K

    1974-01-01

    A reasonable 'microscopic' foundation of the Feynman hadron-liquid analogy is offered, based on a class of models for hadron production. In an external field formalism, the equivalence (complementarity) of the exclusive and inclusive descriptions of hadronic reactions is specifically expressed in a functional-bootstrap form, and integral equations between inclusive and exclusive correlation functions are derived. Using the latest CERN-ISR data on the two-pion inclusive correlation function, and assuming rapidity translational invariance for the exclusive one, the simplest integral equation is solved in the 'central region' and an exclusive correlation length in rapidity predicted. An explanation is also offered for the unexpected similarity observed between pi /sup +/ pi /sup -/ and pi /sup -/ pi /sup -/ inclusive correlations. (31 refs).

  2. Hybrid Nano composite Membranes for PEMFC Applications

    International Nuclear Information System (INIS)

    Niepceron, F.

    2008-03-01

    This work aims at validating a new concept of hybrid materials for the realization of proton exchange membranes, an essential constituent of PEM fuel cells. The originality of this nano-composite hybrid concept corresponds to a separation of the membrane's properties. We investigated the preparation of composite materials based on an inert, relatively low cost, polymer matrix (PVDF-HFP) providing the mechanical stability embedding inorganic fillers providing the necessary properties o f proton-conduction and water retention. The first step of this work consisted in the modification of fumed silica to obtain a proton-conducting filler. An ionic exchange capacity (CEI) equal to 3 meq/g was obtained by the original grafting of sodium poly(styrene-sulfonate) chains from the surface of particles. Nano-composite hybrid membranes PVDF-HFP/functionalized silica were accomplished by a film casting process. The coupling of the morphological and physicochemical analyses validated the percolation of the inorganic phase for 30 wt.% of particles. Beyond 40 % of loading, measured protonic conductivity is higher than the reference membrane Nafion 112. Finally, these membranes presented high performances, above 0.8 W/cm 2 , in single-cell fuel cell tests. A compromise is necessary according to the rate of loading between performances in fuel cell and mechanical properties of the membrane. 50 % appeared as best choice with, until 90 C, a remarkable thermal stability of the performances. (author)

  3. Correlation functions in first-order phase transitions

    Science.gov (United States)

    Garrido, V.; Crespo, D.

    1997-09-01

    Most of the physical properties of systems underlying first-order phase transitions can be obtained from the spatial correlation functions. In this paper, we obtain expressions that allow us to calculate all the correlation functions from the droplet size distribution. Nucleation and growth kinetics is considered, and exact solutions are obtained for the case of isotropic growth by using self-similarity properties. The calculation is performed by using the particle size distribution obtained by a recently developed model (populational Kolmogorov-Johnson-Mehl-Avrami model). Since this model is less restrictive than that used in previously existing theories, the result is that the correlation functions can be obtained for any dependence of the kinetic parameters. The validity of the method is tested by comparison with the exact correlation functions, which had been obtained in the available cases by the time-cone method. Finally, the correlation functions corresponding to the microstructure developed in partitioning transformations are obtained.

  4. Relations between correlation functions in gauge field theory

    International Nuclear Information System (INIS)

    Simonov, Yu. A.; Shevchenko, V. I.

    1997-01-01

    Exact relations between vacuum correlations of non-Abelian field strengths are obtained. With the aid of exterior differentiation, the invariant parts of a given correlation function are expressed in terms of higher order correlation functions. The corollaries of these relations for the behavior of nonperturbative correlation functions at small and large distances are deduced

  5. Screened coulomb hybrid DFT investigation of band gap and optical absorption predictions of CuVO3, CuNbO3 and Cu 5Ta11O30 materials

    KAUST Repository

    Harb, Moussab; Masih, Dilshad; Takanabe, Kazuhiro

    2014-01-01

    with high accuracy using advanced first-principles quantum methods based on DFT (including the perturbation theory approach DFPT) within the screened coulomb hybrid HSE06 exchange-correlation formalism. The calculated density of states are found

  6. A cumulant functional for static and dynamic correlation

    International Nuclear Information System (INIS)

    Hollett, Joshua W.; Hosseini, Hessam; Menzies, Cameron

    2016-01-01

    A functional for the cumulant energy is introduced. The functional is composed of a pair-correction and static and dynamic correlation energy components. The pair-correction and static correlation energies are functionals of the natural orbitals and the occupancy transferred between near-degenerate orbital pairs, rather than the orbital occupancies themselves. The dynamic correlation energy is a functional of the statically correlated on-top two-electron density. The on-top density functional used in this study is the well-known Colle-Salvetti functional. Using the cc-pVTZ basis set, the functional effectively models the bond dissociation of H 2 , LiH, and N 2 with equilibrium bond lengths and dissociation energies comparable to those provided by multireference second-order perturbation theory. The performance of the cumulant functional is less impressive for HF and F 2 , mainly due to an underestimation of the dynamic correlation energy by the Colle-Salvetti functional.

  7. Energy expressions in density-functional theory using line integrals.

    NARCIS (Netherlands)

    van Leeuwen, R.; Baerends, E.J.

    1995-01-01

    In this paper we will address the question of how to obtain energies from functionals when only the functional derivative is given. It is shown that one can obtain explicit expressions for the exchange-correlation energy from approximate exchange-correlation potentials using line integrals along

  8. Exchangers man the pumps: Functional interplay between proton pumps and proton-coupled Ca(2+) exchangers

    Science.gov (United States)

    Tonoplast-localised proton-coupled Ca(2+) transporters encoded by cation/H(+) exchanger (CAX) genes play a critical role in sequestering Ca(2+) into the vacuole. These transporters may function in coordination with Ca(2+) release channels, to shape stimulus-induced cytosolic Ca(2+) elevations. Recen...

  9. A novel hybrid stress-function finite element method immune to severe mesh distortion

    International Nuclear Information System (INIS)

    Cen Song; Zhou Mingjue; Fu Xiangrong

    2010-01-01

    This paper introduces a hybrid stress-function finite element method proposed recently for developing 2D finite element models immune to element shapes. Deferent from the first version of the hybrid-stress element constructed by Pian, the stress function φ of 2D elastic or fracture problem is regarded as the functional variable of the complementary energy functional. Then, the basic analytical solutions of φ are taken as the trial functions for finite element models, and meanwhile, the corresponding unknown stress-function constants are introduced. By using the principle of minimum complementary energy, these unknown stress-function constants can be expressed in terms of the displacements along element edges. Finally, the complementary energy functional can be rewritten in terms of element nodal displacement vector, and thus, the element stiffness matrix of such hybrid-function element can be obtained. As examples, two (8- and 12-node) quadrilateral plane elements and an arbitrary polygonal crack element are constructed by employing different basic analytical solutions of different stress functions. Numerical results show that, the 8- and 12-node plane models can produce the exact solutions for pure bending and linear bending problems, respectively, even the element shape degenerates into triangle and concave quadrangle; and the crack element can also predict accurate results with very low computational cost in analysis of stress-singularity problems.

  10. Non-perturbative QCD correlation functions

    Energy Technology Data Exchange (ETDEWEB)

    Cyrol, Anton Konrad

    2017-11-27

    Functional methods provide access to the non-perturbative regime of quantum chromo- dynamics. Hence, they allow investigating confinement and chiral symmetry breaking. In this dissertation, correlation functions of Yang-Mills theory and unquenched two-flavor QCD are computed from the functional renormalization group. Employing a self-consistent vertex expansion of the effective action, Yang-Mills correlation functions are obtained in four as well as in three spacetime dimensions. To this end, confinement and Slavnov-Taylor identities are discussed. Our numerical results show very good agreement with corresponding lattice results. Next, unquenched two-flavor QCD is considered where it is shown that the unquenched two-flavor gluon propagator is insensitive to the pion mass. Furthermore, the necessity for consistent truncations is emphasized. Finally, correlation functions of finite-temperature Yang-Mills theory are computed in a truncation that includes the splitting of the gluon field into directions that are transverse and longitudinal to the heat bath. In particular, it includes the splitting of the three- and four-gluon vertices. The obtained gluon propagator allows to extract a Debye screening mass that coincides with the hard thermal loop screening mass at high temperatures, but is meaningful also at temperatures below the phase transition temperature.

  11. Heat transfer in plate heat exchanger channels: Experimental validation of selected correlation equations

    Directory of Open Access Journals (Sweden)

    Cieśliński Janusz T.

    2016-09-01

    Full Text Available This study is focused on experimental investigation of selected type of brazed plate heat exchanger (PHEx. The Wilson plot approach was applied in order to estimate heat transfer coefficients for the PHEx passages. The main aim of the paper was to experimentally check ability of several correlations published in the literature to predict heat transfer coefficients by comparison experimentally obtained data with appropriate predictions. The results obtained revealed that Hausen and Dittus-Boelter correlations underestimated heat transfer coefficient for the tested PHEx by an order of magnitude. The Aspen Plate code overestimated heat transfer coefficient by about 50%, while Muley-Manglik correlation overestimated it from 1% to 25%, dependent on the value of Reynolds number and hot or cold liquid side.

  12. Design and simulation of a hybrid ventilation system with earth-air heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Athienitis, A.K.; Zhao, M. [Concordia Univ., Centre for Building Studies, Montreal, PQ (Canada). Dept. of Building, Civil and Environmental Engineering; Roy, M. [Martin Roy and Associes Group Conseil Inc., Montreal, PQ (Canada)

    2005-07-01

    A simulation study was conducted during the design phase of a new circus building in Montreal which includes a hybrid ventilation system through which fresh air is supplied from an earth-air heat exchanger (EAHE). The EAHE has the potential to satisfy the cooling needs of the building and can also be used to preheat fresh air, thereby satisfying one-third or more of the building's heating needs. Another feature of the building is that it uses displacement ventilation by which the air is supplied at low velocities through large diffusers behind the top level seats or under the seats. In this study, computational fluid dynamics (CFD) simulations were carried out to help size the supply and return units of the heating, ventilating and air conditioning (HVAC) system, as well as the exhaust chimney. The primary objective of the CFD simulation was to determine the maximum velocity and temperature in the seated area to ensure thermal comfort. CFD simulation predictions were found to be in good agreement with preliminary measurements taken in the building. In order to monitor the operation of the system over the next year, the underground ducts were equipped with temperature sensors at several depths into the soil. The energy efficiency of the hybrid HVAC system will be assessed and the velocity and temperature distribution in the theatre will be examined under various operating and energy load conditions. 8 refs., 6 figs.

  13. Maximum Mass of Hybrid Stars in the Quark Bag Model

    Science.gov (United States)

    Alaverdyan, G. B.; Vartanyan, Yu. L.

    2017-12-01

    The effect of model parameters in the equation of state for quark matter on the magnitude of the maximum mass of hybrid stars is examined. Quark matter is described in terms of the extended MIT bag model including corrections for one-gluon exchange. For nucleon matter in the range of densities corresponding to the phase transition, a relativistic equation of state is used that is calculated with two-particle correlations taken into account based on using the Bonn meson-exchange potential. The Maxwell construction is used to calculate the characteristics of the first order phase transition and it is shown that for a fixed value of the strong interaction constant αs, the baryon concentrations of the coexisting phases grow monotonically as the bag constant B increases. It is shown that for a fixed value of the strong interaction constant αs, the maximum mass of a hybrid star increases as the bag constant B decreases. For a given value of the bag parameter B, the maximum mass rises as the strong interaction constant αs increases. It is shown that the configurations of hybrid stars with maximum masses equal to or exceeding the mass of the currently known most massive pulsar are possible for values of the strong interaction constant αs > 0.6 and sufficiently low values of the bag constant.

  14. Preparation of zeolite-A/chitosan hybrid composites and their bioactivities and antimicrobial activities.

    Science.gov (United States)

    Yu, Liang; Gong, Jie; Zeng, Changfeng; Zhang, Lixiong

    2013-10-01

    Zeolite-A/chitosan hybrid composites with zeolite contents of 20-55 wt.% were prepared by in situ transformation of silica/chitosan mixtures in a sodium aluminate alkaline solution through impregnation-gelation-hydrothermal synthesis. The products were characterized by X-ray diffraction, diffuse reflectance infrared Fourier transform spectroscopy, scanning electron microscopy, thermogravimetric analysis, and mercury penetration porosimetry. Their in vitro bioactivities were examined using as-synthesized and Ca(2+)-exchanged hybrid composites in simulated body fluid (SBF) for hydroxyapatite (HAP) growth. Their antimicrobial activities for Escherichia coli (E. coli) in trypticase soy broth (TSB) were evaluated using Ag(+)-exchanged hybrid composites. The zeolite-A/chitosan hybrid composites could be prepared as various shapes, including cylinders, plates and thin films. They possessed macropores with pore sizes ranging from 100 to 300 μm and showed compressive mechanical strength as high as 3.2 MPa when the zeolite content was 35 wt.%. Fast growth on the Ca(2+)-exchanged hybrid composites was observed with the highest weight gain of 51.4% in 30 days. The 35 wt.% Ag(+)-exchanged hybrid composite showed the highest antimicrobial activity, which could reduce the 9×10(6) CFU mL(-1)E. coli concentration to zero within 4h of incubation time with the Ag(+)-exchanged hybrid composite amount of 0.4 g L(-1). The bioactivity and antimicrobial activity could be combined by ion-exchanging the composites first with Ca(2+) and then with Ag(+). These zeolite-A/chitosan hybrid composites have potential applications on tissue engineering and antimicrobial food packaging. Copyright © 2013 Elsevier B.V. All rights reserved.

  15. MIL-STD-1553 dynamic bus controller/remote terminal hybrid set

    Science.gov (United States)

    Friedman, S. N.

    This paper describes the performance, physical and electrical requirements of a Dual Redundant BUS Interface Unit (BIU) acting as a BUS Controller Interface Unit (BCIU) or Remote Terminal Unit (RTU) between a Motorola 68000 VME BUS and MIL-STD-1553B Multiplex Data Bus. A discussion of how the BIU Hybrid set is programmed, and operates as a BCIU or RTU, will be included. This paper will review Dynamic Bus Control and other Mode Code capabilities. The BIU Hybrid Set interfaces to a 68000 Microprocessor with a VME Bus using programmed I/O transfers. This special interface will be discussed along with the internal Dual Access Memory (4K x 16) used to support the data exchanges between the CPU and the BIU Hybrid Set. The hybrid set's physical size and power requirements will be covered. This includes the present Double Eurocard the BIU function is presently being offered on.

  16. Oxygen exchange and ice melt measured at the ice-water interface by eddy correlation

    DEFF Research Database (Denmark)

    Long, M.H.; Koopmans, D.; Berg, P.

    2012-01-01

    heterotrophic with a daily gross primary production of 0.69 mmol O2 mĝ̂'2 dĝ̂'1 and a respiration rate of ĝ̂'2.13 mmol O2 mĝ̂'2 dĝ̂'1 leading to a net ecosystem metabolism of ĝ̂'1.45 mmol O2 mĝ̂'2 dĝ̂'1. This application of the eddy correlation technique produced high temporal resolution O2 fluxes and ice melt......This study examined fluxes across the ice-water interface utilizing the eddy correlation technique. Temperature eddy correlation systems were used to determine rates of ice melting and freezing, and O2 eddy correlation systems were used to examine O2 exchange rates driven by biological and physical...

  17. Correlation Functions in Open Quantum-Classical Systems

    Directory of Open Access Journals (Sweden)

    Chang-Yu Hsieh

    2013-12-01

    Full Text Available Quantum time correlation functions are often the principal objects of interest in experimental investigations of the dynamics of quantum systems. For instance, transport properties, such as diffusion and reaction rate coefficients, can be obtained by integrating these functions. The evaluation of such correlation functions entails sampling from quantum equilibrium density operators and quantum time evolution of operators. For condensed phase and complex systems, where quantum dynamics is difficult to carry out, approximations must often be made to compute these functions. We present a general scheme for the computation of correlation functions, which preserves the full quantum equilibrium structure of the system and approximates the time evolution with quantum-classical Liouville dynamics. Several aspects of the scheme are discussed, including a practical and general approach to sample the quantum equilibrium density, the properties of the quantum-classical Liouville equation in the context of correlation function computations, simulation schemes for the approximate dynamics and their interpretation and connections to other approximate quantum dynamical methods.

  18. An open-source framework for analyzing N-electron dynamics. II. Hybrid density functional theory/configuration interaction methodology.

    Science.gov (United States)

    Hermann, Gunter; Pohl, Vincent; Tremblay, Jean Christophe

    2017-10-30

    In this contribution, we extend our framework for analyzing and visualizing correlated many-electron dynamics to non-variational, highly scalable electronic structure method. Specifically, an explicitly time-dependent electronic wave packet is written as a linear combination of N-electron wave functions at the configuration interaction singles (CIS) level, which are obtained from a reference time-dependent density functional theory (TDDFT) calculation. The procedure is implemented in the open-source Python program detCI@ORBKIT, which extends the capabilities of our recently published post-processing toolbox (Hermann et al., J. Comput. Chem. 2016, 37, 1511). From the output of standard quantum chemistry packages using atom-centered Gaussian-type basis functions, the framework exploits the multideterminental structure of the hybrid TDDFT/CIS wave packet to compute fundamental one-electron quantities such as difference electronic densities, transient electronic flux densities, and transition dipole moments. The hybrid scheme is benchmarked against wave function data for the laser-driven state selective excitation in LiH. It is shown that all features of the electron dynamics are in good quantitative agreement with the higher-level method provided a judicious choice of functional is made. Broadband excitation of a medium-sized organic chromophore further demonstrates the scalability of the method. In addition, the time-dependent flux densities unravel the mechanistic details of the simulated charge migration process at a glance. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  19. Functional Principal Components Analysis of Shanghai Stock Exchange 50 Index

    Directory of Open Access Journals (Sweden)

    Zhiliang Wang

    2014-01-01

    Full Text Available The main purpose of this paper is to explore the principle components of Shanghai stock exchange 50 index by means of functional principal component analysis (FPCA. Functional data analysis (FDA deals with random variables (or process with realizations in the smooth functional space. One of the most popular FDA techniques is functional principal component analysis, which was introduced for the statistical analysis of a set of financial time series from an explorative point of view. FPCA is the functional analogue of the well-known dimension reduction technique in the multivariate statistical analysis, searching for linear transformations of the random vector with the maximal variance. In this paper, we studied the monthly return volatility of Shanghai stock exchange 50 index (SSE50. Using FPCA to reduce dimension to a finite level, we extracted the most significant components of the data and some relevant statistical features of such related datasets. The calculated results show that regarding the samples as random functions is rational. Compared with the ordinary principle component analysis, FPCA can solve the problem of different dimensions in the samples. And FPCA is a convenient approach to extract the main variance factors.

  20. Reference Determinant Dependence of the Random Phase Approximation in 3d Transition Metal Chemistry.

    Science.gov (United States)

    Bates, J E; Mezei, P D; Csonka, G I; Sun, J; Ruzsinszky, A

    2017-01-10

    Without extensive fitting, accurate prediction of transition metal chemistry is a challenge for semilocal and hybrid density funcitonals. The Random Phase Approximation (RPA) has been shown to yield superior results to semilocal functionals for main group thermochemistry, but much less is known about its performance for transition metals. We have therefore analyzed the behavior of reaction energies, barrier heights, and ligand dissociation energies obtained with RPA and compare our results to several semilocal and hybrid functionals. Particular attention is paid to the reference determinant dependence of RPA. We find that typically the results do not vary much between semilocal or hybrid functionals as a reference, as long as the fraction of exact exchange (EXX) mixing in the hybrid functional is small. For large fractions of EXX mixing, however, the Hartree-Fock-like nature of the determinant can severely degrade the performance. Overall, RPA systematically reduces the errors of semilocal functionals and delivers excellent performance from a single reference determinant for inherently multireference reactions. The behavior of dual hybrids that combine RPA correlation with a hybrid exchange energy was also explored, but ultimately did not lead to a systematic improvement compared to traditional RPA for these systems. We rationalize this conclusion by decomposing the contributions to the reaction energies, and briefly discuss the possible implications for double-hybrid functionals based on RPA. The correlation between EXX mixing and spin-symmetry breaking is also discussed.

  1. Beyond the random-phase approximation for the electron correlation energy: the importance of single excitations.

    Science.gov (United States)

    Ren, Xinguo; Tkatchenko, Alexandre; Rinke, Patrick; Scheffler, Matthias

    2011-04-15

    The random-phase approximation (RPA) for the electron correlation energy, combined with the exact-exchange (EX) energy, represents the state-of-the-art exchange-correlation functional within density-functional theory. However, the standard RPA practice--evaluating both the EX and the RPA correlation energies using Kohn-Sham (KS) orbitals from local or semilocal exchange-correlation functionals--leads to a systematic underbinding of molecules and solids. Here we demonstrate that this behavior can be corrected by adding a "single excitation" contribution, so far not included in the standard RPA scheme. A similar improvement can also be achieved by replacing the non-self-consistent EX total energy by the corresponding self-consistent Hartree-Fock total energy, while retaining the RPA correlation energy evaluated using KS orbitals. Both schemes achieve chemical accuracy for a standard benchmark set of noncovalent intermolecular interactions.

  2. Perturbed angular correlation study of the ion exchange of indium into silicalite zeolites

    Energy Technology Data Exchange (ETDEWEB)

    Ramallo-Lopez, J.M., E-mail: requejo@venus.fisica.unlp.edu.ar; Requejo, F.G., E-mail: requejo@venus.fisica.unlp.edu.ar; Renteria, M., E-mail: requejo@venus.fisica.unlp.edu.ar; Bibiloni, A.G. [UNLP, Programa TENAES (CONICET) and Departamento de Fisica, Faculdad Cs Ex (Argentina)], E-mail: requejo@venus.fisica.unlp.edu.ar; Miro, E.E. [UNL, INCAPE (CONICET) and Faculdad Ing. Quimica (Argentina)

    1999-09-15

    Two indium-containing silicalite zeolites (In/H-ZSM5) catalysts prepared by wet impregnation and ionic exchange were characterized by the Perturbed Angular Correlation (PAC) technique using {sup 111}In as probe to determine the nature of the indium species. Some of these species take part in the catalytic reaction of the selective reduction (SCR) of NO{sub x} with methane. PAC experiments were performed at 500 deg. C in air before and after reduction-reoxidation treatments on the catalysts in order to determine the origin of the different hyperfine interactions and then the degree of ionic exchange. Complementary catalytic activity characterizations were also performed.PAC experiments performed on the catalyst obtained by wet impregnation showed that all In-atoms form In{sub 2}O{sub 3} crystallites while almost 70% of In-atoms form In{sub 2}O{sub 3} in the catalyst obtained by ionic exchange. The PAC experiments of both catalysts performed after the reduction-reoxidation treatment revealed the presence of two hyperfine interactions, different from those corresponding to indium in In{sub 2}O{sub 3}. These hyperfine interactions should be associated to disperse In species responsible of the catalytic activity located in the ionic exchange-sites of the zeolites.

  3. Generalized oscillator strength for the argon 3p6-3p5 4s transition: Correlation and exchange effects on the characteristic minimum

    International Nuclear Information System (INIS)

    Chen, Zhifan; Msezane, Alfred Z.; Amusia, M. Ya.

    1999-01-01

    We have investigated the generalized oscillator strength (GOS) for a transition of the type np→(n+1)s, where n is the principal quantum number of the outermost filled shell of the atomic ground state, using the random-phase approximation with exchange. We find that the influence of correlation and exchange effects on the position of the characteristic minimum in the GOS of Ar(n=3) is insignificant. Also, our first Born approximation predicts the position of the minimum accurately provided that accurate target wave functions are employed. Our results agree excellently with measurements and are expected to be applicable equally to the corresponding subshells of Ne(n=2), Kr(n=4), and Xe(n=5). (c) 1999 The American Physical Society

  4. The normal function of a speciation gene, Odysseus, and its hybrid sterility effect.

    Science.gov (United States)

    Sun, Sha; Ting, Chau-Ti; Wu, Chung-I

    2004-07-02

    To understand how postmating isolation is connected to the normal process of species divergence and why hybrid male sterility is often the first sign of speciation, we analyzed the Odysseus (OdsH) gene of hybrid male sterility in Drosophila. We carried out expression analysis, transgenic study, and gene knockout. The combined evidence suggests that the sterility phenotype represents a novel manifestation of the gene function rather than the reduction or loss of the normal one. The gene knockout experiment identified the normal function of OdsH as a modest enhancement of sperm production in young males. The implication of a weak effect of OdsH on the normal phenotype but a strong influence on hybrid male sterility is discussed in light of Haldane's rule of postmating isolation.

  5. Simultaneous acquisition for T2 -T2 Exchange and T1 -T2 correlation NMR experiments

    Science.gov (United States)

    Montrazi, Elton T.; Lucas-Oliveira, Everton; Araujo-Ferreira, Arthur G.; Barsi-Andreeta, Mariane; Bonagamba, Tito J.

    2018-04-01

    The NMR measurements of longitudinal and transverse relaxation times and its multidimensional correlations provide useful information about molecular dynamics. However, these experiments are very time-consuming, and many researchers proposed faster experiments to reduce this issue. This paper presents a new way to simultaneously perform T2 -T2 Exchange and T1 -T2 correlation experiments by taking the advantage of the storage time and the two steps phase cycling used for running the relaxation exchange experiment. The data corresponding to each step is either summed or subtracted to produce the T2 -T2 and T1 -T2 data, enhancing the information obtained while maintaining the experiment duration. Comparing the results from this technique with traditional NMR experiments it was possible to validate the method.

  6. Magnetic exchange couplings from noncollinear perturbation theory: dinuclear CuII complexes.

    Science.gov (United States)

    Phillips, Jordan J; Peralta, Juan E

    2014-08-07

    To benchmark the performance of a new method based on noncollinear coupled-perturbed density functional theory [J. Chem. Phys. 138, 174115 (2013)], we calculate the magnetic exchange couplings in a series of triply bridged ferromagnetic dinuclear Cu(II) complexes that have been recently synthesized [Phys. Chem. Chem. Phys. 15, 1966 (2013)]. We find that for any basis-set the couplings from our noncollinear coupled-perturbed methodology are practically identical to those of spin-projected energy-differences when a hybrid density functional approximation is employed. This demonstrates that our methodology properly recovers a Heisenberg description for these systems, and is robust in its predictive power of magnetic couplings. Furthermore, this indicates that the failure of density functional theory to capture the subtle variation of the exchange couplings in these complexes is not simply an artifact of broken-symmetry methods, but rather a fundamental weakness of current approximate density functionals for the description of magnetic couplings.

  7. Calcium exchange, structure, and function in cultured adult myocardial cells

    International Nuclear Information System (INIS)

    Langer, G.A.; Frank, J.S.; Rich, T.L.; Orner, F.B.

    1987-01-01

    Cells digested from adult rat heart and cultured for 14 days demonstrate all the structural elements, in mature form, associated with the process of excitation-contraction (EC) coupling. The transverse tubular (TT) system is well developed with an extensive junctional sarcoplasmic reticulum (JSR). In nonphosphate-containing buffer contraction of the cells is lost as rapidly as zero extracellular Ca concentration ([Ca] 0 ) solution is applied and a negative contraction staircase is produced on increase of stimulation frequency. Structurally and functionally the cells have the characteristics of adult cells in situ. 45 Ca exchange and total 45 Ca measurement in N-2-hydroxyethylpiperazine N'-2-ethanesulfonic acid (HEPES)-buffered perfusate define three components of cellular Ca: 1) a rapidly exchangeable component accounting for 36% of total Ca, 2) a slowly exchangeable component (t/sub 1/2/ 53 min) accounting for 7% total Ca, and 3) the remaining 57% cellular Ca is inexchangeable (demonstrates no significant exchange within 60 min). The slowly exchangeable component can be increased 10-fold within 60 min by addition of phosphate to the perfusate. The Ca distribution and exchange characteristics are little different from those of 3-day cultures of neonatal rat heart previously studied. The results suggest that the cells are representative of adult cells in situ and that both sarcolemmal-bound and sarcoplasmic reticular Ca contribute to the component of Ca that is rapidly exchangeable

  8. Correlation functions of two-matrix models

    International Nuclear Information System (INIS)

    Bonora, L.; Xiong, C.S.

    1993-11-01

    We show how to calculate correlation functions of two matrix models without any approximation technique (except for genus expansion). In particular we do not use any continuum limit technique. This allows us to find many solutions which are invisible to the latter technique. To reach our goal we make full use of the integrable hierarchies and their reductions which were shown in previous papers to naturally appear in multi-matrix models. The second ingredient we use, even though to a lesser extent, are the W-constraints. In fact an explicit solution of the relevant hierarchy, satisfying the W-constraints (string equation), underlies the explicit calculation of the correlation functions. The correlation functions we compute lend themselves to a possible interpretation in terms of topological field theories. (orig.)

  9. Correlation function of the luminosity distances

    Energy Technology Data Exchange (ETDEWEB)

    Biern, Sang Gyu; Yoo, Jaiyul, E-mail: sgbiern@physik.uzh.ch, E-mail: jyoo@physik.uzh.ch [Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science, University of Zürich, Winterthurerstrasse 190, CH-8057, Zürich (Switzerland)

    2017-09-01

    We present the correlation function of the luminosity distances in a flat ΛCDM universe. Decomposing the luminosity distance fluctuation into the velocity, the gravitational potential, and the lensing contributions in linear perturbation theory, we study their individual contributions to the correlation function. The lensing contribution is important at large redshift ( z ∼> 0.5) but only for small angular separation (θ ∼< 3°), while the velocity contribution dominates over the other contributions at low redshift or at larger separation. However, the gravitational potential contribution is always subdominant at all scale, if the correct gauge-invariant expression is used. The correlation function of the luminosity distances depends significantly on the matter content, especially for the lensing contribution, thus providing a novel tool of estimating cosmological parameters.

  10. High infection control rate and function after routine one-stage exchange for chronically infected TKA.

    Science.gov (United States)

    Jenny, Jean-Yves; Barbe, Bruno; Gaudias, Jeannot; Boeri, Cyril; Argenson, Jean-Noël

    2013-01-01

    Many surgeons consider two-stage exchange the gold standard for treating chronic infection after TKA. One-stage exchange is an alternative for infection control and might provide better knee function, but the rates of infection control and levels of function are unclear. We asked whether a one-stage exchange protocol would lead to infection control rates and knee function similar to those after two-stage exchange. We followed all 47 patients with chronically infected TKAs treated with one-stage exchange between July 2004 and February 2007. We monitored for recurrence of infection and obtained Knee Society Scores. We followed patients a minimum of 3 years or until death or infection recurrence. Three of the 47 patients (6%) experienced a persistence or recurrence of the index infection with the same pathogen isolated. Three patients (6%) had control of the index infection but between 6 and 17 months experienced an infection with another pathogen. The 3-year survival rates were 87% for being free of any infection and 91% for being healed of the index infection. Twenty-five of the 45 patients (56%) had a Knee Society Score of more than 150 points. While routine one-stage exchange was not associated with a higher rate of infection recurrence failure, knee function was not improved compared to that of historical patients having two-stage exchange. One stage-exchange may be a reasonable alternative in chronically infected TKA as a more convenient approach for patients without the risks of two operations and hospitalizations and for reducing costs. The ideal one stage-exchange candidate should be identified in future studies.

  11. Research overview : design specifications for hybrid vehicles

    NARCIS (Netherlands)

    Hofman, T.; Druten, van R.M.

    2004-01-01

    In this paper a method is proposed for determination of the design specifications regarding the energy exchange systems for different chargesustaining hybrid vehicles of different vehicle classes. Hybrid drivetrains for vehicles combine multiple power sources in order to increase the driving

  12. ABC's of pion charge exchange

    International Nuclear Information System (INIS)

    Gibbs, W.R.; Kaufmann, W.B.; Siegel, P.B.

    1985-01-01

    Calculations of pion single charge exchange using the PWIA and DWIA are presented. Emphasis is given to the effects of absorbtion and blocking. A microscopic calculation of the 0 0 excitation and low energy angular distribution is in excellent agreement with the data. A fixed nucleon multiple scattering calculation of the pion double charge exchange reaction is presented. Various valence neutron wave functions are used, and the contributions of different spatial orientations of the last two neutrons to the reaction are examined. The DCX cross section is found to be very sensitive to the inclusion of correlations in the two-neutron wave function. Satisfactory agreement with DCX data on 14 C can be obtained using a nucleonic picture of the nucleus

  13. Exchange-correlation energy in the orbital occupancy method: electronic structure of organic molecules

    International Nuclear Information System (INIS)

    Oszwaldowski, R; Vazquez, H; Pou, P; Ortega, J; Perez, R; Flores, F

    2003-01-01

    A new DF-LCAO (density functional with local combination of atomic orbitals) method is used to calculate the electronic properties of 3,4,9,10 perylenetetracarboxylic dianhydride (PTCDA), C 6 H 6 , CH 4 , and CO. The method, called the OO (orbital occupancy) method, is a DF-based theory, which uses the OOs instead of ρ(r) to calculate the exchange and correlation energies. In our calculations, we compare the OO method with the conventional local density approximation approach. Our results show that, using a minimal basis set, we obtain equilibrium bond lengths and binding energies for PTCDA, C 6 H 6 , and CH 4 which are respectively within 6, and 10-15% of the experimental values. We have also calculated the affinity and ionization levels, as well as the optical gap, for benzene and PTCDA and have found that a variant of Koopmans' theorem works well for these molecules. Using this theorem we calculate the Koopmans relaxation energies of the σ- and π-orbitals for PTCDA and have obtained this molecule's density of states which compares well with experimental evidence

  14. New correlation potential for the local-spin-density functional formalism. II

    International Nuclear Information System (INIS)

    Kolar, M.; Farkas, L.

    1982-01-01

    Using the new parameterization for the correlation potential which seems to be the best that is at present available within the local-spin-density (LSD) functional formalism, the Fermi contact term in light atoms (up to Ni) is calculated. Although the overall improvement of the previous LSD results is obtained, discrepancy between theory and experiment remains rather large. It seems that the local approximation for exchange and correlation fails to predict such quantities as magnetic-moment density near the nucleus. It is also shown that the self-interaction correction does not remedy this failure. Further, the effect of the nonzero nuclear radius is investigated and found to be most important in the lightest atoms (e.g. a factor of 0.664 appears in the case of Li). This fact was omitted in all previous calculations and throws doubt on the reported excellent agreement of the results of many-body perturbation theory with experiment. It was also verified that the contact approximation of the Fermi contact term is really good enough. (author)

  15. THE HYBRID APPROACH OF INFLATION TARGETING: WHAT OPPORTUNITIES FOR AN EMERGING ECONOMY LIKE TUNISIA?

    Directory of Open Access Journals (Sweden)

    Hella Guerchi Mehri

    2016-07-01

    Full Text Available After economic crises happening in many emerging countries, flexible exchange rates became a required theoretical condition helping to target inflation. Many countries stopped using exchange rate as an anchor for monetary policy and started using inflation targeting framework. In emerging countries, monetary authorities work to stabilize the exchange rate because of their “fear of floating”. They are against high volatility of interest rate allowing speculative attacks and causing free fluctuations of their national currency. To avoid uncontrolled market movements, they have to choose between active and public exchange rate management and tight inflation targeting. In the same vein, Central bank of Tunisia follows financial measures linked closely to inflation without focusing especially on monetary aggregates in order to study a possible transition to targeting inflation strategy. It uses a simple Taylor rule where interest rates adjustment are guided by the anticipated inflation deviation from its original target and also by the gap between observed and potential GDP.As an emerging economy with a high degree of financial vulnerability, and facing different shocks, Tunisia should adopt a hybrid rule of inflation targeting in an open economy. This hybrid rule explicitly takes into account the evolution of the exchange rate in the reaction function of the central bank.

  16. Nucleon-nucleon momentum correlation function for light nuclei

    International Nuclear Information System (INIS)

    Ma, Y.G.; Cai, X.Z.; Chen, J.G.; Fang, D.Q.; Guo, W.; Liu, G.H.; Ma, C.W.; Ma, E.J.; Shen, W.Q.; Shi, Y.; Su, Q.M.; Tian, W.D.; Wang, H.W.; Wang, K.; Wei, Y.B.; Yan, T.Z.

    2007-01-01

    Nucleon-nucleon momentum correlation function have been presented for nuclear reactions with neutron-rich or proton-rich projectiles using a nuclear transport theory, namely Isospin-Dependent Quantum Molecular Dynamics model. The relationship between the binding energy of projectiles and the strength of proton-neutron correlation function at small relative momentum has been explored, while proton-proton correlation function shows its sensitivity to the proton density distribution. Those results show that nucleon-nucleon correlation function is useful to reflect some features of the neutron- or proton-halo nuclei and therefore provide a potential tool for the studies of radioactive beam physics

  17. Magnetization reversal and domain correlation for a non-collinear and out-of-plane exchange-coupled system

    International Nuclear Information System (INIS)

    Paul, Amitesh; Paul, N; Mattauch, Stefan

    2011-01-01

    We have investigated the impact of out-of-plane ferromagnetic (FM) anisotropy (which can be coincident with the direction of unidirectional anisotropy), where antiferromagnetic (AF) anisotropy is along the film plane. This provides a platform for non-collinear exchange coupling in an archetypal exchange coupled system in an unconventional way. We probe the in-plane magnetization by the depth-sensitive vector magnetometry technique. The experimental findings reveal a magnetization reversal (i) that is symmetric for both the branches of the hysteresis loop, (ii) that is characterized by vertically correlated domains associated with a strong transverse component of magnetization and (iii) that remains untrained (suppression of trained state) with field cycling. This scenario has been compared with in-plane magnetization reversal for a conventional in-plane unidirectional anisotropic case in the same system that shows usual asymmetric reversal and training for vertically uncorrelated domains. We explain the above observations for the out-of-plane case in terms of inhomogeneous magnetic states due to competing perpendicular anisotropies that result in non-collinear FM-AF coupling. This study provides direct evidence for the vertical correlation of domains mediated by out-of-plane exchange coupling.

  18. The correlation function for density perturbations in an expanding universe. IV - The evolution of the correlation function. [galaxy distribution

    Science.gov (United States)

    Mcclelland, J.; Silk, J.

    1979-01-01

    The evolution of the two-point correlation function for the large-scale distribution of galaxies in an expanding universe is studied on the assumption that the perturbation densities lie in a Gaussian distribution centered on any given mass scale. The perturbations are evolved according to the Friedmann equation, and the correlation function for the resulting distribution of perturbations at the present epoch is calculated. It is found that: (1) the computed correlation function gives a satisfactory fit to the observed function in cosmological models with a density parameter (Omega) of approximately unity, provided that a certain free parameter is suitably adjusted; (2) the power-law slope in the nonlinear regime reflects the initial fluctuation spectrum, provided that the density profile of individual perturbations declines more rapidly than the -2.4 power of distance; and (3) both positive and negative contributions to the correlation function are predicted for cosmological models with Omega less than unity.

  19. A continuous exchange factor method for radiative exchange in enclosures with participating media

    International Nuclear Information System (INIS)

    Naraghi, M.H.N.; Chung, B.T.F.; Litkouhi, B.

    1987-01-01

    A continuous exchange factor method for analysis of radiative exchange in enclosures is developed. In this method two types of exchange functions are defined, direct exchange function and total exchange function. Certain integral equations relating total exchange functions to direct exchange functions are developed. These integral equations are solved using Gaussian quadrature integration method. The results obtained based on the present approach are found to be more accurate than those of the zonal method

  20. Development of an exchange–correlation functional with uncertainty quantification capabilities for density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Aldegunde, Manuel, E-mail: M.A.Aldegunde-Rodriguez@warwick.ac.uk; Kermode, James R., E-mail: J.R.Kermode@warwick.ac.uk; Zabaras, Nicholas

    2016-04-15

    This paper presents the development of a new exchange–correlation functional from the point of view of machine learning. Using atomization energies of solids and small molecules, we train a linear model for the exchange enhancement factor using a Bayesian approach which allows for the quantification of uncertainties in the predictions. A relevance vector machine is used to automatically select the most relevant terms of the model. We then test this model on atomization energies and also on bulk properties. The average model provides a mean absolute error of only 0.116 eV for the test points of the G2/97 set but a larger 0.314 eV for the test solids. In terms of bulk properties, the prediction for transition metals and monovalent semiconductors has a very low test error. However, as expected, predictions for types of materials not represented in the training set such as ionic solids show much larger errors.

  1. Preparation of zeolite-A/chitosan hybrid composites and their bioactivities and antimicrobial activities

    International Nuclear Information System (INIS)

    Yu, Liang; Gong, Jie; Zeng, Changfeng; Zhang, Lixiong

    2013-01-01

    Zeolite-A/chitosan hybrid composites with zeolite contents of 20–55 wt.% were prepared by in situ transformation of silica/chitosan mixtures in a sodium aluminate alkaline solution through impregnation–gelation–hydrothermal synthesis. The products were characterized by X-ray diffraction, diffuse reflectance infrared Fourier transform spectroscopy, scanning electron microscopy, thermogravimetric analysis, and mercury penetration porosimetry. Their in vitro bioactivities were examined using as-synthesized and Ca 2+ -exchanged hybrid composites in simulated body fluid (SBF) for hydroxyapatite (HAP) growth. Their antimicrobial activities for Escherichia coli (E. coli) in trypticase soy broth (TSB) were evaluated using Ag + -exchanged hybrid composites. The zeolite-A/chitosan hybrid composites could be prepared as various shapes, including cylinders, plates and thin films. They possessed macropores with pore sizes ranging from 100 to 300 μm and showed compressive mechanical strength as high as 3.2 MPa when the zeolite content was 35 wt.%. Fast growth on the Ca 2+ -exchanged hybrid composites was observed with the highest weight gain of 51.4% in 30 days. The 35 wt.% Ag + -exchanged hybrid composite showed the highest antimicrobial activity, which could reduce the 9 × 10 6 CFU mL −1 E. coli concentration to zero within 4 h of incubation time with the Ag + -exchanged hybrid composite amount of 0.4 g L −1 . The bioactivity and antimicrobial activity could be combined by ion-exchanging the composites first with Ca 2+ and then with Ag + . These zeolite-A/chitosan hybrid composites have potential applications on tissue engineering and antimicrobial food packaging. - Graphical abstract: Zeolite A/chitosan hybrid composites were prepared by in situ transformation of precursors in the chitosan matrix, which possess macroporous structures and exhibit superior bioactivity and antimicrobial activity and potential biomedical application. Highlights: • Zeolite A

  2. Preparation of zeolite-A/chitosan hybrid composites and their bioactivities and antimicrobial activities

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Liang; Gong, Jie [State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009 (China); Zeng, Changfeng [College of Mechanic and Power Engineering, Nanjing University of Technology, Nanjing 210009 (China); Zhang, Lixiong, E-mail: lixiongzhang@yahoo.com [State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009 (China)

    2013-10-15

    Zeolite-A/chitosan hybrid composites with zeolite contents of 20–55 wt.% were prepared by in situ transformation of silica/chitosan mixtures in a sodium aluminate alkaline solution through impregnation–gelation–hydrothermal synthesis. The products were characterized by X-ray diffraction, diffuse reflectance infrared Fourier transform spectroscopy, scanning electron microscopy, thermogravimetric analysis, and mercury penetration porosimetry. Their in vitro bioactivities were examined using as-synthesized and Ca{sup 2+}-exchanged hybrid composites in simulated body fluid (SBF) for hydroxyapatite (HAP) growth. Their antimicrobial activities for Escherichia coli (E. coli) in trypticase soy broth (TSB) were evaluated using Ag{sup +}-exchanged hybrid composites. The zeolite-A/chitosan hybrid composites could be prepared as various shapes, including cylinders, plates and thin films. They possessed macropores with pore sizes ranging from 100 to 300 μm and showed compressive mechanical strength as high as 3.2 MPa when the zeolite content was 35 wt.%. Fast growth on the Ca{sup 2+}-exchanged hybrid composites was observed with the highest weight gain of 51.4% in 30 days. The 35 wt.% Ag{sup +}-exchanged hybrid composite showed the highest antimicrobial activity, which could reduce the 9 × 10{sup 6} CFU mL{sup −1}E. coli concentration to zero within 4 h of incubation time with the Ag{sup +}-exchanged hybrid composite amount of 0.4 g L{sup −1}. The bioactivity and antimicrobial activity could be combined by ion-exchanging the composites first with Ca{sup 2+} and then with Ag{sup +}. These zeolite-A/chitosan hybrid composites have potential applications on tissue engineering and antimicrobial food packaging. - Graphical abstract: Zeolite A/chitosan hybrid composites were prepared by in situ transformation of precursors in the chitosan matrix, which possess macroporous structures and exhibit superior bioactivity and antimicrobial activity and potential biomedical

  3. Correlation structures in short-term variabilities of stock indices and exchange rates

    Science.gov (United States)

    Nakamura, Tomomichi; Small, Michael

    2007-09-01

    Financial data usually show irregular fluctuations and some trends. We investigate whether there are correlation structures in short-term variabilities (irregular fluctuations) among financial data from the viewpoint of deterministic dynamical systems. Our method is based on the small-shuffle surrogate method. The data we use are daily closing price of Standard & Poor's 500 and the volume, and daily foreign exchange rates, Euro/US Dollar (USD), British Pound/USD and Japanese Yen/USD. We found that these data are not independent.

  4. Graphene-based hybrid structures combined with functional materials of ferroelectrics and semiconductors.

    Science.gov (United States)

    Jie, Wenjing; Hao, Jianhua

    2014-06-21

    Fundamental studies and applications of 2-dimensional (2D) graphene may be deepened and broadened via combining graphene sheets with various functional materials, which have been extended from the traditional insulator of SiO2 to a versatile range of dielectrics, semiconductors and metals, as well as organic compounds. Among them, ferroelectric materials have received much attention due to their unique ferroelectric polarization. As a result, many attractive characteristics can be shown in graphene/ferroelectric hybrid systems. On the other hand, graphene can be integrated with conventional semiconductors and some newly-discovered 2D layered materials to form distinct Schottky junctions, yielding fascinating behaviours and exhibiting the potential for various applications in future functional devices. This review article is an attempt to illustrate the most recent progress in the fabrication, operation principle, characterization, and promising applications of graphene-based hybrid structures combined with various functional materials, ranging from ferroelectrics to semiconductors. We focus on mechanically exfoliated and chemical-vapor-deposited graphene sheets integrated in numerous advanced devices. Some typical hybrid structures have been highlighted, aiming at potential applications in non-volatile memories, transparent flexible electrodes, solar cells, photodetectors, and so on.

  5. Generalized hydrodynamic correlations and fractional memory functions

    Science.gov (United States)

    Rodríguez, Rosalio F.; Fujioka, Jorge

    2015-12-01

    A fractional generalized hydrodynamic (GH) model of the longitudinal velocity fluctuations correlation, and its associated memory function, for a complex fluid is analyzed. The adiabatic elimination of fast variables introduces memory effects in the transport equations, and the dynamic of the fluctuations is described by a generalized Langevin equation with long-range noise correlations. These features motivate the introduction of Caputo time fractional derivatives and allows us to calculate analytic expressions for the fractional longitudinal velocity correlation function and its associated memory function. Our analysis eliminates a spurious constant term in the non-fractional memory function found in the non-fractional description. It also produces a significantly slower power-law decay of the memory function in the GH regime that reduces to the well-known exponential decay in the non-fractional Navier-Stokes limit.

  6. Multifractal detrended cross-correlation analysis on gold, crude oil and foreign exchange rate time series

    Science.gov (United States)

    Pal, Mayukha; Madhusudana Rao, P.; Manimaran, P.

    2014-12-01

    We apply the recently developed multifractal detrended cross-correlation analysis method to investigate the cross-correlation behavior and fractal nature between two non-stationary time series. We analyze the daily return price of gold, West Texas Intermediate and Brent crude oil, foreign exchange rate data, over a period of 18 years. The cross correlation has been measured from the Hurst scaling exponents and the singularity spectrum quantitatively. From the results, the existence of multifractal cross-correlation between all of these time series is found. We also found that the cross correlation between gold and oil prices possess uncorrelated behavior and the remaining bivariate time series possess persistent behavior. It was observed for five bivariate series that the cross-correlation exponents are less than the calculated average generalized Hurst exponents (GHE) for q0 and for one bivariate series the cross-correlation exponent is greater than GHE for all q values.

  7. Correlation analysis of the Korean stock market: Revisited to consider the influence of foreign exchange rate

    Science.gov (United States)

    Jo, Sang Kyun; Kim, Min Jae; Lim, Kyuseong; Kim, Soo Yong

    2018-02-01

    We investigated the effect of foreign exchange rate in a correlation analysis of the Korean stock market using both random matrix theory and minimum spanning tree. We collected data sets which were divided into two types of stock price, the original stock price in Korean Won and the price converted into US dollars at contemporary foreign exchange rates. Comparing the random matrix theory based on the two different prices, a few particular sectors exhibited substantial differences while other sectors changed little. The particular sectors were closely related to economic circumstances and the influence of foreign financial markets during that period. The method introduced in this paper offers a way to pinpoint the effect of exchange rate on an emerging stock market.

  8. A comparative density functional study on electrical properties of layered penta-graphene

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Zhi Gen, E-mail: yuzg@ihpc.a-star.edu.sg; Zhang, Yong-Wei, E-mail: zhangyw@ihpc.a-star.edu.sg [Institute of High Performance Computing, Singapore 138632 (Singapore)

    2015-10-28

    We present a comparative study of the influence of the number of layers, the biaxial strain in the range of −3% to 3%, and the stacking misalignments on the electronic properties of a new 2D carbon allotrope, penta-graphene (PG), based on hybrid-functional method within the density functional theory (DFT). In comparison with local exchange-correlation approximation in the DFT, the hybrid-functional provides an accurate description on the degree of p{sub z} orbitals localization and bandgap. Importantly, the predicted bandgap of few-layer PG has a weak layer dependence. The bandgap of monolayer PG is 3.27 eV, approximately equal to those of GaN and ZnO; and the bandgap of few-layer PG decreases slowly with the number of layers (N) and converge to 2.57 eV when N ≥ 4. Our calculations using HSE06 functional on few-layer PG reveal that bandgap engineering by stacking misalignment can further tune the bandgap down to 1.37 eV. Importantly, there is no direct-to-indirect bandgap transition in PG by varying strain, layer number, and stacking misalignment. Owing to its tunable, robustly direct, and wide bandgap characteristics, few-layer PG is promising for optoelectronic and photovoltaic applications.

  9. Hartree and Exchange in Ensemble Density Functional Theory: Avoiding the Nonuniqueness Disaster.

    Science.gov (United States)

    Gould, Tim; Pittalis, Stefano

    2017-12-15

    Ensemble density functional theory is a promising method for the efficient and accurate calculation of excitations of quantum systems, at least if useful functionals can be developed to broaden its domain of practical applicability. Here, we introduce a guaranteed single-valued "Hartree-exchange" ensemble density functional, E_{Hx}[n], in terms of the right derivative of the universal ensemble density functional with respect to the coupling constant at vanishing interaction. We show that E_{Hx}[n] is straightforwardly expressible using block eigenvalues of a simple matrix [Eq. (14)]. Specialized expressions for E_{Hx}[n] from the literature, including those involving superpositions of Slater determinants, can now be regarded as originating from the unifying picture presented here. We thus establish a clear and practical description for Hartree and exchange in ensemble systems.

  10. Hybrid cooling tower Neckarwestheim 2 cooling function, emission, plume dispersion

    International Nuclear Information System (INIS)

    Braeuning, G.; Ernst, G.; Maeule, R.; Necker, P.

    1990-01-01

    The fan-assisted hybrid cooling tower of the 1300 MW power plant Gemeinschafts-Kernkraftwerk Neckarwestheim 2 was designed and constructed based on results from theoretical and experimental studies and experiences from a smaller prototype. The wet part acts in counterflow. The dry part is arranged above the wet part. Each part contains 44 fans. Special attention was payed to the ducts which mix the dry into the wet plume. The cooling function and state, mass flow and contents of the emission were measured. The dispersion of the plume in the atmosphere was observed. The central results are presented in this paper. The cooling function corresponds to the predictions. The content of drifted cooling water in the plume is extremely low. The high velocity of the plume in the exit causes an undisturbed flow into the atmosphere. The hybrid operation reduces visible plumes strongly, especially in warmer and drier ambient air

  11. IMPROVING CORRELATION FUNCTION FITTING WITH RIDGE REGRESSION: APPLICATION TO CROSS-CORRELATION RECONSTRUCTION

    International Nuclear Information System (INIS)

    Matthews, Daniel J.; Newman, Jeffrey A.

    2012-01-01

    Cross-correlation techniques provide a promising avenue for calibrating photometric redshifts and determining redshift distributions using spectroscopy which is systematically incomplete (e.g., current deep spectroscopic surveys fail to obtain secure redshifts for 30%-50% or more of the galaxies targeted). In this paper, we improve on the redshift distribution reconstruction methods from our previous work by incorporating full covariance information into our correlation function fits. Correlation function measurements are strongly covariant between angular or spatial bins, and accounting for this in fitting can yield substantial reduction in errors. However, frequently the covariance matrices used in these calculations are determined from a relatively small set (dozens rather than hundreds) of subsamples or mock catalogs, resulting in noisy covariance matrices whose inversion is ill-conditioned and numerically unstable. We present here a method of conditioning the covariance matrix known as ridge regression which results in a more well behaved inversion than other techniques common in large-scale structure studies. We demonstrate that ridge regression significantly improves the determination of correlation function parameters. We then apply these improved techniques to the problem of reconstructing redshift distributions. By incorporating full covariance information, applying ridge regression, and changing the weighting of fields in obtaining average correlation functions, we obtain reductions in the mean redshift distribution reconstruction error of as much as ∼40% compared to previous methods. We provide a description of POWERFIT, an IDL code for performing power-law fits to correlation functions with ridge regression conditioning that we are making publicly available.

  12. Triplet state photochemistry and the three-state crossing of acetophenone within time-dependent density-functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Huix-Rotllant, Miquel, E-mail: miquel.huix@gmail.com; Ferré, Nicolas, E-mail: nicolas.ferre@univ-amu.fr [Institut de Chimie Radicalaire (UMR-7273), Aix-Marseille Université, CNRS, 13397 Marseille Cedex 20 (France)

    2014-04-07

    Even though time-dependent density-functional theory (TDDFT) works generally well for describing excited states energies and properties in the Franck-Condon region, it can dramatically fail in predicting photochemistry, notably when electronic state crossings occur. Here, we assess the ability of TDDFT to describe the photochemistry of an important class of triplet sensitizers, namely, aromatic ketones. We take acetophenone as a test molecule, for which accurate ab initio results exist in the literature. Triplet acetophenone is generated thanks to an exotic three-state crossing involving one singlet and two triplets states (i.e., a simultaneous intersystem crossing and triplet conical intersection), thus being a stringent test for approximate TDDFT. We show that most exchange-correlation functionals can only give a semi-qualitative picture of the overall photochemistry, in which the three-state crossing is rather represented as a triplet conical intersection separated from the intersystem crossing. The best result overall is given by the double hybrid functional mPW2PLYP, which is even able to reproduce quantitatively the three-state crossing region. We rationalize this results by noting that double hybrid functionals include a larger portion of double excitation character to the excited states.

  13. A hybrid approach for short-term forecasting of wind speed.

    Science.gov (United States)

    Tatinati, Sivanagaraja; Veluvolu, Kalyana C

    2013-01-01

    We propose a hybrid method for forecasting the wind speed. The wind speed data is first decomposed into intrinsic mode functions (IMFs) with empirical mode decomposition. Based on the partial autocorrelation factor of the individual IMFs, adaptive methods are then employed for the prediction of IMFs. Least squares-support vector machines are employed for IMFs with weak correlation factor, and autoregressive model with Kalman filter is employed for IMFs with high correlation factor. Multistep prediction with the proposed hybrid method resulted in improved forecasting. Results with wind speed data show that the proposed method provides better forecasting compared to the existing methods.

  14. Establishment of hybridized focus measure functions as a universal method for autofocusing

    Science.gov (United States)

    Shah, Mohammad Imran; Mishra, Smriti; Rout, Chittaranjan

    2017-12-01

    Exact focusing is essential for any automatic image capturing system. Performances of focus measure functions (FMFs) used for autofocusing are sensitive to image contents and imaging systems. Therefore, identification of universal FMF assumes a lot of significance. Eight FMFs were hybridized in pairs of two and implemented simultaneously on a single stack to calculate the hybrid focus measure. In total, 28 hybrid FMFs (HFMFs) and eight FMFs were implemented on stacks of images from three different imaging modalities. Performance of FMFs was found to the best at 50% region sampling. Accuracy, focus error, and false maxima were calculated to evaluate the performance of each FMF. Nineteen HFMFs provided >90% accuracy. Image distortion (noise, contrast, saturation, illumination, etc.) was performed to evaluate robustness of HFMFs. Hybrid of tenengrad variance and steerable filter-based (VGRnSFB) FMFs was identified as the most robust and accurate function with an accuracy of ≥90% and a relatively lower focus error and false maxima rate. Sharpness of focus curve of VGRnSFB along with eight individual FMFs was also computed to determine the efficacy of HFMF for the optimization process. VGRnSFB HFMF may be implemented for automated capturing of an image for any imaging system.

  15. Spinor exchange in AdSd+1

    International Nuclear Information System (INIS)

    Kawano, Teruhiko; Okuyama, Kazumi

    2000-01-01

    We explicitly calculate a Witten diagram with general spinor field exchange on (d+1)-dimensional Euclidean Anti-de Sitter space, which is necessary to evaluate four-point correlation functions with spinor fields when we make use of the AdS/CFT correspondence, especially in supersymmetric cases. We also show that the amplitude can be reduced to a scalar exchange amplitude. We discuss the operator product expansion of the dual conformal field theory by interpreting the short distance expansion of the amplitude according to the AdS/CFT correspondence

  16. Hydrogen Exchange Differences between Chemoreceptor Signaling Complexes Localize to Functionally Important Subdomains

    Science.gov (United States)

    2015-01-01

    The goal of understanding mechanisms of transmembrane signaling, one of many key life processes mediated by membrane proteins, has motivated numerous studies of bacterial chemotaxis receptors. Ligand binding to the receptor causes a piston motion of an α helix in the periplasmic and transmembrane domains, but it is unclear how the signal is then propagated through the cytoplasmic domain to control the activity of the associated kinase CheA. Recent proposals suggest that signaling in the cytoplasmic domain involves opposing changes in dynamics in different subdomains. However, it has been difficult to measure dynamics within the functional system, consisting of extended arrays of receptor complexes with two other proteins, CheA and CheW. We have combined hydrogen exchange mass spectrometry with vesicle template assembly of functional complexes of the receptor cytoplasmic domain to reveal that there are significant signaling-associated changes in exchange, and these changes localize to key regions of the receptor involved in the excitation and adaptation responses. The methylation subdomain exhibits complex changes that include slower hydrogen exchange in complexes in a kinase-activating state, which may be partially consistent with proposals that this subdomain is stabilized in this state. The signaling subdomain exhibits significant protection from hydrogen exchange in complexes in a kinase-activating state, suggesting a tighter and/or larger interaction interface with CheA and CheW in this state. These first measurements of the stability of protein subdomains within functional signaling complexes demonstrate the promise of this approach for measuring functionally important protein dynamics within the various physiologically relevant states of multiprotein complexes. PMID:25420045

  17. Stable carbon isotope composition (δ{sup 13}C), water use efficiency, and biomass productivity of Lycopersicon esculentum, Lycopersicon pennellii, and the F{sub 1} hybrid

    Energy Technology Data Exchange (ETDEWEB)

    Martin, B.; Thorstenson, Y. R.

    1988-09-01

    Three tomatoes, Lycopersicon esculentum Mill. cv UC82B, a droughttolerant wild related species, Lycopersicon pennellii (Cor.) D'Arcy, and their F{sub 1}, hybrid, were grown in containers maintained at three levels of soil moisture. Season-long water use was obtained by summing over the season daily weight losses of each container corrected for soil evaporation. Plant biomass was determined by harvesting and weighing entire dried plants. Season-long water use efficiency (gram dry weight/kilogram H{sub 2}O) was calculated by dividing the dry biomass by the season-long water use. The season-long water use efficiency was greatest in the wild parent, poorest in the domestic parent, and intermediate (but closer to the wild parent) in the F, hybrid. Instantaneous water-use efficiency (micromole CO{sub 2}/millimole H{sub 2}O) determined by gas exchange measurements on individual leaves was poorly correlated with season-long water use efficiency. However, the relative abundance of stable carbon isotopes of leaf tissue samples was strongly correlated with the season-long water use efficiency. Also, the isotopic composition and the season-long water use efficiency of each genotype alone were strongly negatively correlated with plant dry weight when the dry weight varied as a function of soil moisture. (author)

  18. Correlation Functions in Open Quantum-Classical Systems

    OpenAIRE

    Hsieh, Chang-Yu; Kapral, Raymond

    2013-01-01

    Quantum time correlation functions are often the principal objects of interest in experimental investigations of the dynamics of quantum systems. For instance, transport properties, such as diffusion and reaction rate coefficients, can be obtained by integrating these functions. The evaluation of such correlation functions entails sampling from quantum equilibrium density operators and quantum time evolution of operators. For condensed phase and complex systems, where quantum dynamics is diff...

  19. Spin and orbital exchange interactions from Dynamical Mean Field Theory

    Energy Technology Data Exchange (ETDEWEB)

    Secchi, A., E-mail: a.secchi@science.ru.nl [Radboud University, Institute for Molecules and Materials, 6525 AJ Nijmegen (Netherlands); Lichtenstein, A.I., E-mail: alichten@physnet.uni-hamburg.de [Universitat Hamburg, Institut für Theoretische Physik, Jungiusstraße 9, D-20355 Hamburg (Germany); Katsnelson, M.I., E-mail: m.katsnelson@science.ru.nl [Radboud University, Institute for Molecules and Materials, 6525 AJ Nijmegen (Netherlands)

    2016-02-15

    We derive a set of equations expressing the parameters of the magnetic interactions characterizing a strongly correlated electronic system in terms of single-electron Green's functions and self-energies. This allows to establish a mapping between the initial electronic system and a spin model including up to quadratic interactions between the effective spins, with a general interaction (exchange) tensor that accounts for anisotropic exchange, Dzyaloshinskii–Moriya interaction and other symmetric terms such as dipole–dipole interaction. We present the formulas in a format that can be used for computations via Dynamical Mean Field Theory algorithms. - Highlights: • We give formulas for the exchange interaction tensor in strongly correlated systems. • Interactions are written in terms of electronic Green's functions and self-energies. • The method is suitable for a Dynamical Mean Field Theory implementation. • No quenching of the orbital magnetic moments is assumed. • Spin and orbital contributions to magnetism can be computed separately.

  20. Conception and fabrication of a real time automatic correlator (multi-correlator)

    International Nuclear Information System (INIS)

    Berthier, D.

    1967-10-01

    The purpose of this work is to elaborate a specific computer able to display the real.time correlation function of two variables represented by two electrical signals. The various functions to be done are dealt with the best suited technology: delays from numerical method, hybrid multiplication, analog integration. This method proved very versatile so that it has been possible to modify the circuits with more performing components without changing the general conception of the whole system. In particular, the bandwidth, which was originally 125 kHz (1966) is now 1 MHz and will be 5 MHz, January 1968. Many results are obtained from the correlator such as: - determination of pulse responses of linear systems (1. and 2. order filters, oscillating circuits); - extraction of signals from noise; - measurement of time and space correlation in a turbulent plasma; - treatment of electro-biological signals. (author) [fr

  1. Spin-orbit ZORA and four-component Dirac-Coulomb estimation of relativistic corrections to isotropic nuclear shieldings and chemical shifts of noble gas dimers

    DEFF Research Database (Denmark)

    Jankowska, Marzena; Kupka, Teobald; Stobiński, Leszek

    2016-01-01

    Hartree-Fock and density functional theory with the hybrid B3LYP and general gradient KT2 exchange-correlation functionals were used for non-relativistic and relativistic nuclear magnetic shielding calculations of helium, neon, argon, krypton and xenon dimers and free atoms. Relativistic...

  2. 42 CFR 476.86 - Correlation of Title XI functions with Title XVIII functions.

    Science.gov (United States)

    2010-10-01

    ... 42 Public Health 4 2010-10-01 2010-10-01 false Correlation of Title XI functions with Title XVIII functions. 476.86 Section 476.86 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF...) Qio Review Functions § 476.86 Correlation of Title XI functions with Title XVIII functions. (a...

  3. Electronic structure, magnetism, and exchange integrals in transition-metal oxides: Role of the spin polarization of the functional in DFT+U calculations

    Science.gov (United States)

    Keshavarz, Samara; Schött, Johan; Millis, Andrew J.; Kvashnin, Yaroslav O.

    2018-05-01

    Density functional theory augmented with Hubbard-U corrections (DFT+U ) is currently one of the most widely used methods for first-principles electronic structure modeling of insulating transition-metal oxides (TMOs). Since U is relatively large compared to bandwidths, the magnetic excitations in TMOs are expected to be well described by a Heisenberg model. However, in practice the calculated exchange parameters Ji j depend on the magnetic configuration from which they are extracted and on the functional used to compute them. In this work we investigate how the spin polarization dependence of the underlying exchange-correlation functional influences the calculated magnetic exchange constants of TMOs. We perform a systematic study of the predictions of calculations based on the local density approximation plus U (LDA+U ) and the local spin density approximation plus U (LSDA+U ) for the electronic structures, total energies, and magnetic exchange interactions Ji j extracted from ferromagnetic (FM) and antiferromagnetic (AFM) configurations of several transition-metal oxide materials. We report that for realistic choices of Hubbard U and Hund's J parameters, LSDA+U and LDA+U calculations result in different values of the magnetic exchange constants and band gap. The dependence of the band gap on the magnetic configuration is stronger in LDA+U than in LSDA+U and we argue that this is the main reason why the configuration dependence of Ji j is found to be systematically more pronounced in LDA+U than in LSDA+U calculations. We report a very good correspondence between the computed total energies and the parametrized Heisenberg model for LDA+U calculations, but not for LSDA+U , suggesting that LDA+U is a more appropriate method for estimating exchange interactions.

  4. Time-dependent reduced density matrix functional theory applied to laser-driven, correlated two-electron dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Brics, Martins; Kapoor, Varun; Bauer, Dieter [Institut fuer Physik, Universitaet Rostock, 18051 Rostock (Germany)

    2013-07-01

    Time-dependent density functional theory (TDDFT) with known and practicable exchange-correlation potentials does not capture highly correlated electron dynamics such as single-photon double ionization, autoionization, or nonsequential ionization. Time-dependent reduced density matrix functional theory (TDRDMFT) may remedy these problems. The key ingredients in TDRDMFT are the natural orbitals (NOs), i.e., the eigenfunctions of the one-body reduced density matrix (1-RDM), and the occupation numbers (OCs), i.e., the respective eigenvalues. The two-body reduced density matrix (2-RDM) is then expanded in NOs, and equations of motion for the NOs can be derived. If the expansion coefficients of the 2-RDM were known exactly, the problem at hand would be solved. In practice, approximations have to be made. We study the prospects of TDRDMFT following a top-down approach. We solve the exact two-electron time-dependent Schroedinger equation for a model Helium atom in intense laser fields in order to study highly correlated phenomena such as the population of autoionizing states or single-photon double ionization. From the exact wave function we calculate the exact NOs, OCs, the exact expansion coefficients of the 2-RDM, and the exact potentials in the equations of motion. In that way we can identify how many NOs and which level of approximations are necessary to capture such phenomena.

  5. Algebraic relaxation of a time correlation function

    International Nuclear Information System (INIS)

    Srivastava, S.; Kumar, C.N.; Tankeshwar, K.

    2004-06-01

    A second order non-linear differential equation obtained from Mori's integro- differential equation is shown to transform to another form which provides algebraic decay to a time correlation function. Involved parameters in algebraic formula are related to exact properties of the corresponding correlation function. The model has been used to study a sol-gel system which is known, experimentally, to exhibit a power law decay to stress auto-correlation function. The expression obtained for the viscosity shows a logarithmic divergence at some critical value of the parameter. Some features of the model have also been tested using available information about Lennard-Jones fluids. (author)

  6. Mechanical Behavior of Nanostructured Hybrids Based on Poly(Vinyl Alcohol/Bioactive Glass Reinforced with Functionalized Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    H. S. Mansur

    2012-01-01

    Full Text Available This study reports the synthesis and characterization of novel tridimensional porous hybrids based on PVA combined with bioactive glass and reinforced by chemically functionalized carbon nanotubes (CNT for potential use in bone tissue engineering. The functionalization of CNT was performed by introducing carboxylic groups in multiwall nanotubes. This process aimed at enhancing the affinity of CNTs with the water-soluble PVA polymer derived by the hydrogen bonds formed among alcohol (PVA and carboxylic groups (CNT–COOH. In the sequence, the CNT–COOH (0.25 wt% were used as the nanostructure modifier for the hybrid system based on PVA associated with the bioactive glass (BaG. The mechanical properties of the nanostructured hybrids reinforced with CNT–COOH were evaluated by axial compression tests, and they were compared to reference hybrid. The averaged yield stresses of macroporous hybrids were (2.3 ± 0.9 and (4.4 ± 1.0 MPa for the reference and the CNT reinforced materials, respectively. Moreover, yield strain and Young's modulus were significantly enhanced by about 30% for the CNT–COOH hybrids. Hence, as far as the mechanical properties are concerned, the results have clearly showed the feasibility of utilizing these new hybrids reinforced with functionalized CNT in repairing cancellous bone tissues.

  7. Reactivity of the functional groups in functional polymers. Use of T-for-H exchange reaction

    International Nuclear Information System (INIS)

    Imaizumi, Hiroshi; Hasegawa, Shinobu.

    1997-01-01

    In order to reveal the reactivity of several functional polymers, the following two experiments were carried out: observing the hydrogen-isotope exchange reaction (T-for-H exchange reaction) between one of T-labeled functional polymers and 0.500 mol·l -1 aniline dissolved in p-xylene, observing the degree of the T dispersed from the surface area of the polymer under the several conditions. Consequently, the following six matters have been quantitatively obtained. The T-for-H exchange reaction occurred between each T-labeled polymer and aniline, and is more predominant than other chemical reactions within the range of 50-90degC. The reactivity of the polymers are strongly affected by their matrix structures. The degree of the T dispersed from the surface area of each T-labeled polymer is hardly affected by humidity. The higher the temperature is, the larger is the degree of the T dispersed from the surface area. At the same temperature, the degree of the T dispersed from the surface area of each polymer is strongly affected by the physical form of the polymer even if the polymer has the same functional group as the others, and the T existing in the surface area of a T-labeled glassy polymer is less dispersed than that of a porous one. The degree of the T dispersed from the surface area of a T-labeled polymer is small when the degree of the polymerization of the polymer is high. (author)

  8. Increased abundance of insulin/insulin-like growth factor-I hybrid receptors in skeletal muscle of obese subjects is correlated with in vivo insulin sensitivity.

    Science.gov (United States)

    Federici, M; Porzio, O; Lauro, D; Borboni, P; Giovannone, B; Zucaro, L; Hribal, M L; Sesti, G

    1998-08-01

    We reported that in noninsulin-dependent diabetes melitus (NIDDM) patients expression of insulin/insulin-like growth factor I (IGF-I) hybrid receptors is increased in insulin target tissues. Whether this is a defect associated with NIDDM or represents a generalized abnormality associated with insulin resistant states is still unsettled. To address this, we applied a microwell-based immunoassay to measure abundance of insulin receptors, type 1 IGF receptors, and hybrid receptors in muscle of eight normal and eight obese subjects. Maximal insulin binding to insulin receptors was lower in obese than in control subjects (B/T = 1.8 +/- 0.20 and 2.6 +/- 0.30; P < 0.03, respectively) and was negatively correlated with insulinemia (r = -0.60; P < 0.01). Maximal IGF-I binding to type 1 IGF receptors was higher in obese than in controls (B/T = 1.9 +/- 0.20 and 0.86 +/- 0.10; P < 0.0001, respectively) and was negatively correlated with plasma IGF-I levels (r = -0.69; P < 0.003). Hybrid receptor abundance was higher in obese than in normal subjects (B/T = 1.21 +/- 0.14 and 0.44 +/- 0.06; P < 0.0003, respectively) and was negatively correlated with insulin binding (r = -0.60; P < 0.01) and positively correlated with IGF-I binding (r = 0.92; P < 0.0001). Increased abundance of hybrids was correlated with insulinemia (r = 0.70; P < 0.002) and body mass index (r = 0.71; P < 0.0019), whereas it was negatively correlated with in vivo insulin sensitivity measured by ITT (r = -0.67; P < 0.016). These results indicate that downregulation of insulin receptors or upregulation of type 1 IGF receptors because of changes in plasma insulin and IGF-I levels may result in modifications in hybrid receptor abundance.

  9. Chromatin Structure and Radiation-Induced Intrachromosome Exchange

    Science.gov (United States)

    Mangala; Zhang, Ye; Hada, Megumi; Cucinotta, Francis A.; Wu, Honglu

    2011-01-01

    We have recently investigated the location of breaks involved in intrachromosomal type exchange events, using the multicolor banding in situ hybridization (mBAND) technique for human chromosome 3. In human epithelial cells exposed to both low- and high-LET radiations in vitro, intrachromosome exchanges were found to occur preferentially between a break in the 3p21 and one in the 3q11. Exchanges were also observed between a break in 3p21 and one in 3q26, but few exchanges were observed between breaks in 3q11 and 3q26, even though the two regions were on the same arm of the chromosome. To explore the relationships between intrachromosome exchanges and chromatin structure, we used probes that hybridize the three regions of 3p21, 3q11 and 3q26, and measured the distance between two of the three regions in interphase cells. We further analyzed fragile sites on the chromosome that have been identified in various types of cancers. Our results demonstrated that the distribution of breaks involved in radiation-induced intrachromosome aberrations depends upon both the location of fragile sites and the folding of chromatins

  10. Separation and determination of arsenic species in water by selective exchange and hybrid resins

    Energy Technology Data Exchange (ETDEWEB)

    Issa, Nureddin Ben [Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, Belgrade (Serbia); Rajakovic-Ognjanovic, Vladana N. [Faculty of Civil Engineering, University of Belgrade, Bulevar Kralja Aleksandra 73, Belgrade (Serbia); Marinkovic, Aleksandar D. [Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, Belgrade (Serbia); Rajakovic, Ljubinka V., E-mail: ljubinka@tmf.bg.ac.rs [Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, Belgrade (Serbia)

    2011-11-07

    Highlights: {yields} A simple and efficient method for separation and determination of arsenic species. {yields} A new hybrid resin HY-AgCl is effective for iAs and oAs analytical separation. {yields} SBAE resin was convenient for the separation of As(III) from As(V) and oAs species. {yields} HY-Fe resin was convenient for the separation of DMAs(V). - Abstract: A simple and efficient method for separation and determination of inorganic arsenic (iAs) and organic arsenic (oAs) in drinking, natural and wastewater was developed. If arsenic is present in water prevailing forms are inorganic acids of As(III) and As(V). oAs can be found in traces as monomethylarsenic acid, MMA(V), and dimethylarsenic acid, DMAs(V). Three types of resins: a strong base anion exchange (SBAE) and two hybrid (HY) resins: HY-Fe and HY-AgCl, based on the activity of hydrated iron oxides and a silver chloride were investigated. It was found that the sorption processes (ion exchange, adsorption and chemisorptions) of arsenic species on SBAE (ion exchange) and HY resins depend on pH values of water. The quantitative separation of molecular and ionic forms of iAs and oAs was achieved by SBAE and pH adjustment, the molecular form of As(III) that exists in the water at pH <8.0 was not bonded with SBAE, which was convenient for direct determination of As(III) concentration in the effluent. HY-Fe resin retained all arsenic species except DMAs(V), which makes possible direct measurements of this specie in the effluent. HY-AgCl resin retained all iAs which was convenient for direct determination of oAs species concentration in the effluent. The selective bonding of arsenic species on three types of resins makes possible the development of the procedure for measuring and calculation of all arsenic species in water. In order to determine capacity of resins the preliminary investigations were performed in batch system and fixed bed flow system. Resin capacities were calculated according to breakthrough

  11. Application of an excited state LDA exchange energy functional for the calculation of transition energy of atoms within time-independent density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Shamim, Md; Harbola, Manoj K, E-mail: sami@iitk.ac.i, E-mail: mkh@iitk.ac.i [Department of Physics, Indian Institute of Technology, Kanpur 208 016 (India)

    2010-11-14

    Transition energies of a new class of excited states (two-gap systems) of various atoms are calculated in time-independent density functional formalism by using a recently proposed local density approximation exchange energy functional for excited states. It is shown that the excitation energies calculated with this functional compare well with those calculated with exact exchange theories.

  12. Application of an excited state LDA exchange energy functional for the calculation of transition energy of atoms within time-independent density functional theory

    International Nuclear Information System (INIS)

    Shamim, Md; Harbola, Manoj K

    2010-01-01

    Transition energies of a new class of excited states (two-gap systems) of various atoms are calculated in time-independent density functional formalism by using a recently proposed local density approximation exchange energy functional for excited states. It is shown that the excitation energies calculated with this functional compare well with those calculated with exact exchange theories.

  13. Memory functions and correlations in additive binary Markov chains

    Energy Technology Data Exchange (ETDEWEB)

    Melnyk, S S [A Ya Usikov Institute for Radiophysics and Electronics, Ukrainian Academy of Science, 12 Proskura Street, 61085 Kharkov (Ukraine); Usatenko, O V [A Ya Usikov Institute for Radiophysics and Electronics, Ukrainian Academy of Science, 12 Proskura Street, 61085 Kharkov (Ukraine); Yampol' skii, V A [A Ya Usikov Institute for Radiophysics and Electronics, Ukrainian Academy of Science, 12 Proskura Street, 61085 Kharkov (Ukraine); Apostolov, S S [V N Karazin Kharkov National University, 4 Svoboda Sq., Kharkov 61077 (Ukraine); Maiselis, Z A [V N Karazin Kharkov National University, 4 Svoboda Sq., Kharkov 61077 (Ukraine)

    2006-11-17

    A theory of additive Markov chains with a long-range memory, proposed earlier in Usatenko et al (2003 Phys. Rev. E 68 061107), is developed and used to describe statistical properties of long-range correlated systems. The convenient characteristics of such systems, memory functions and their relation to the correlation properties of the systems are examined. Various methods for finding the memory function via the correlation function are proposed. The inverse problem (calculation of the correlation function by means of the prescribed memory function) is also solved. This is demonstrated for the analytically solvable model of the system with a step-wise memory function.

  14. Memory functions and correlations in additive binary Markov chains

    International Nuclear Information System (INIS)

    Melnyk, S S; Usatenko, O V; Yampol'skii, V A; Apostolov, S S; Maiselis, Z A

    2006-01-01

    A theory of additive Markov chains with a long-range memory, proposed earlier in Usatenko et al (2003 Phys. Rev. E 68 061107), is developed and used to describe statistical properties of long-range correlated systems. The convenient characteristics of such systems, memory functions and their relation to the correlation properties of the systems are examined. Various methods for finding the memory function via the correlation function are proposed. The inverse problem (calculation of the correlation function by means of the prescribed memory function) is also solved. This is demonstrated for the analytically solvable model of the system with a step-wise memory function

  15. Soft Sensing of Key State Variables in Fermentation Process Based on Relevance Vector Machine with Hybrid Kernel Function

    Directory of Open Access Journals (Sweden)

    Xianglin ZHU

    2014-06-01

    Full Text Available To resolve the online detection difficulty of some important state variables in fermentation process with traditional instruments, a soft sensing modeling method based on relevance vector machine (RVM with a hybrid kernel function is presented. Based on the characteristic analysis of two commonly-used kernel functions, that is, local Gaussian kernel function and global polynomial kernel function, a hybrid kernel function combing merits of Gaussian kernel function and polynomial kernel function is constructed. To design optimal parameters of this kernel function, the particle swarm optimization (PSO algorithm is applied. The proposed modeling method is used to predict the value of cell concentration in the Lysine fermentation process. Simulation results show that the presented hybrid-kernel RVM model has a better accuracy and performance than the single kernel RVM model.

  16. Linear response at the 4-component relativistic density-functional level: application to the frequency-dependent dipole polarizability of Hg, AuH and PtH2

    International Nuclear Information System (INIS)

    Salek, Pawel; Helgaker, Trygve; Saue, Trond

    2005-01-01

    We report the implementation and application of linear response density-functional theory (DFT) based on the 4-component relativistic Dirac-Coulomb Hamiltonian. The theory is cast in the language of second quantization and is based on the quasienergy formalism (Floquet theory), replacing the initial state dependence of the Runge-Gross theorem by periodic boundary conditions. Contradictions in causality and symmetry of the time arguments are thereby avoided and the exchange-correlation potential and kernel can be expressed as functional derivatives of the quasienergy. We critically review the derivation of the quasienergy analogues of the Hohenberg-Kohn theorem and the Kohn-Sham formalism and discuss the nature of the quasienergy exchange-correlation functional. Structure is imposed on the response equations in terms of Hermiticity and time-reversal symmetry. It is observed that functionals of spin and current densities, corresponding to time-antisymmetric operators, contribute to frequency-dependent and not static electric properties. Physically, this follows from the fact that only a time-dependent electric field creates a magnetic field. It is furthermore observed that hybrid functionals enhance spin polarization since only exact exchange contributes to anti-Hermitian trial vectors. We apply 4-component relativistic linear response DFT to the calculation of the frequency-dependent polarizability of the isoelectronic series Hg, AuH and PtH 2 . Unlike for the molecules, the effect of electron correlation on the polarizability of the mercury atom is very large, about 25%. We observe a remarkable performance of the local-density approximation (LDA) functional in reproducing the experimental frequency-dependent polarizability of this atom, clearly superior to that of the BLYP and B3LYP functionals. This allows us to extract Cauchy moments (S(-4) = 382.82 and S(-6) = 6090.89 a.u.) that we believe are superior to experiment since we go to higher order in the Cauchy

  17. Towards an ankle neuroprosthesis for hybrid robotics: Concepts and current sources for functional electrical stimulation.

    Science.gov (United States)

    Casco, S; Fuster, I; Galeano, R; Moreno, J C; Pons, J L; Brunetti, F

    2017-07-01

    Hybrid rehabilitation robotics combine neuro-prosthetic devices (close-loop functional electrical stimulation systems) and traditional robotic structures and actuators to explore better therapies and promote a more efficient motor function recovery or compensation. Although hybrid robotics and ankle neuroprostheses (NPs) have been widely developed over the last years, there are just few studies on the use of NPs to electrically control both ankle flexion and extension to promote ankle recovery and improved gait patterns in paretic limbs. The aim of this work is to develop an ankle NP specifically designed to work in the field of hybrid robotics. This article presents early steps towards this goal and makes a brief review about motor NPs and Functional Electrical Stimulation (FES) principles and most common devices used to aid the ankle functioning during the gait cycle. It also shows a current sources analysis done in this framework, in order to choose the best one for this intended application.

  18. New One-Boson-Exchange Potential functions | Fiase | Journal of ...

    African Journals Online (AJOL)

    A new one-boson-exchange potential (OBEP) is derived by fitting the oscillator matrix elements of the sum of the OBEP functions to those of the matrix elements derived by the lowest order constrained variational (LOCV) technique. The results give a reasonable fit to the OBEP model. Journal of the Nigerian Association of ...

  19. Generalized oscillator strength for the argon 3p{sup 6}-3p{sup 5} 4s transition: Correlation and exchange effects on the characteristic minimum

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhifan [Center for Theoretical Studies of Physical Systems, and Department of Physics, Clark Atlanta University, Atlanta, Georgia 30314 (United States); Msezane, Alfred Z. [Center for Theoretical Studies of Physical Systems, and Department of Physics, Clark Atlanta University, Atlanta, Georgia 30314 (United States); Amusia, M. Ya. [Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, (Israel)

    1999-12-01

    We have investigated the generalized oscillator strength (GOS) for a transition of the type np{yields}(n+1)s, where n is the principal quantum number of the outermost filled shell of the atomic ground state, using the random-phase approximation with exchange. We find that the influence of correlation and exchange effects on the position of the characteristic minimum in the GOS of Ar(n=3) is insignificant. Also, our first Born approximation predicts the position of the minimum accurately provided that accurate target wave functions are employed. Our results agree excellently with measurements and are expected to be applicable equally to the corresponding subshells of Ne(n=2), Kr(n=4), and Xe(n=5). (c) 1999 The American Physical Society.

  20. 78 FR 58354 - Self-Regulatory Organizations; Chicago Board Options Exchange, Incorporated; Notice of Filing and...

    Science.gov (United States)

    2013-09-23

    ... AA classes based on several factors, including competitive forces and trading volume.\\3\\ The Exchange... electronically in additional Hybrid option classes. The Exchange believes this may result in more competitive pricing in IWM and other Hybrid option classes, which will promote just and equitable principles of trade...

  1. The correlation between dual-color chromogenic in situ hybridization and fluorescence in situ hybridization in assessing HER2 gene amplification in breast cancer.

    Science.gov (United States)

    Pedersen, Marianne; Rasmussen, Birgitte Bruun

    2009-06-01

    Fluorescence in situ hybridization (FISH) is regarded as the gold standard method for detecting HER2 gene amplification. Chromogenic in situ hybridization (CISH) is a promising alternative to FISH because CISH has the advantages of being a method evaluated by bright-field microscopy and the generated chromogenic signals are also stable. This study presents a dual color CISH for simultaneous detection of the HER2 gene and chromosome 17. The CISH method performs a chromogenic detection "on top" of the Food and Drug Administration (FDA)-approved HER2 FISH pharmDx method, where the fluorochrome-labeled probes are detected using enzyme-labeled antibodies and visualized by chromogenic enzymatic reactions. The HER2 status (amplified/not amplified and HER2 ratios) was evaluated by the CISH method and compared with results obtained by the FDA-approved FISH method. Of the 72 successfully investigated invasive breast carcinomas, both FISH and CISH detected HER2 amplification in 24 cases and nonamplification was detected in 47 cases. One case showed a discrepancy between FISH and CISH. The concordance between CISH and FISH was found to be almost perfect (98.6%). The correlation between the HER2 ratios obtained by the 2 methods showed excellent correlation (correlation coefficient 0.95). In conclusion, it is possible by dual-color CISH method to demonstrate HER2 genes and chromosome 17 genes, in the same tissue section and reliably assess HER2 status. The CISH method is a very promising alternative to the FISH method.

  2. Electronic correlation studies. III. Self-correlated field method. Application to 2S ground state and 2P excited state of three-electron atomic systems

    International Nuclear Information System (INIS)

    Lissillour, R.; Guerillot, C.R.

    1975-01-01

    The self-correlated field method is based on the insertion in the group product wave function of pair functions built upon a set of correlated ''local'' functions and of ''nonlocal'' functions. This work is an application to three-electron systems. The effects of the outer electron on the inner pair are studied. The total electronic energy and some intermediary results such as pair energies, Coulomb and exchange ''correlated'' integrals, are given. The results are always better than those given by conventional SCF computations and reach the same level of accuracy as those given by more laborious methods used in correlation studies. (auth)

  3. Structural and functional cerebral correlates of hypnotic suggestibility.

    Directory of Open Access Journals (Sweden)

    Alexa Huber

    Full Text Available Little is known about the neural bases of hypnotic suggestibility, a cognitive trait referring to the tendency to respond to hypnotic suggestions. In the present magnetic resonance imaging study, we performed regression analyses to assess hypnotic suggestibility-related differences in local gray matter volume, using voxel-based morphometry, and in waking resting state functional connectivity of 10 resting state networks, in 37 healthy women. Hypnotic suggestibility was positively correlated with gray matter volume in portions of the left superior and medial frontal gyri, roughly overlapping with the supplementary and pre-supplementary motor area, and negatively correlated with gray matter volume in the left superior temporal gyrus and insula. In the functional connectivity analysis, hypnotic suggestibility was positively correlated with functional connectivity between medial posterior areas, including bilateral posterior cingulate cortex and precuneus, and both the lateral visual network and the left fronto-parietal network; a positive correlation was also found with functional connectivity between the executive-control network and a right postcentral/parietal area. In contrast, hypnotic suggestibility was negatively correlated with functional connectivity between the right fronto-parietal network and the right lateral thalamus. These findings demonstrate for the first time a correlation between hypnotic suggestibility, the structural features of specific cortical regions, and the functional connectivity during the normal resting state of brain structures involved in imagery and self-monitoring activity.

  4. Structural and functional cerebral correlates of hypnotic suggestibility.

    Science.gov (United States)

    Huber, Alexa; Lui, Fausta; Duzzi, Davide; Pagnoni, Giuseppe; Porro, Carlo Adolfo

    2014-01-01

    Little is known about the neural bases of hypnotic suggestibility, a cognitive trait referring to the tendency to respond to hypnotic suggestions. In the present magnetic resonance imaging study, we performed regression analyses to assess hypnotic suggestibility-related differences in local gray matter volume, using voxel-based morphometry, and in waking resting state functional connectivity of 10 resting state networks, in 37 healthy women. Hypnotic suggestibility was positively correlated with gray matter volume in portions of the left superior and medial frontal gyri, roughly overlapping with the supplementary and pre-supplementary motor area, and negatively correlated with gray matter volume in the left superior temporal gyrus and insula. In the functional connectivity analysis, hypnotic suggestibility was positively correlated with functional connectivity between medial posterior areas, including bilateral posterior cingulate cortex and precuneus, and both the lateral visual network and the left fronto-parietal network; a positive correlation was also found with functional connectivity between the executive-control network and a right postcentral/parietal area. In contrast, hypnotic suggestibility was negatively correlated with functional connectivity between the right fronto-parietal network and the right lateral thalamus. These findings demonstrate for the first time a correlation between hypnotic suggestibility, the structural features of specific cortical regions, and the functional connectivity during the normal resting state of brain structures involved in imagery and self-monitoring activity.

  5. Correlation between apparent diffusion coefficients and standardized uptake values in hybrid {sup 18}F-FDG PET/MR: Preliminary results in rectal cancer

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Ju Hye [Dept. of Nuclear Medicine, Kyungpook National University Hospital, Daegu (Korea, Republic of); Cho, Ihn Ho; Chun, Kyung Ah; Kong, Eun Jung; Kwon, Sang Don; Kim, Jae Hwang [Yeungnam University Hospital, Daegu (Korea, Republic of)

    2016-06-15

    Fluorine-18-fluorodeoxyglucose ({sup 18}F-FDG) positron emission tomography (PET) and diffusion-weighted magnetic resonance imaging (DWI) share the same role in clinical oncology and it is feasible to obtain the standardized uptake value (SUV) and apparent diffusion coefficient (ADC) simultaneously by emerging the hybrid positron emission tomography/magnetic resonance (PET/MR). This study investigated the correlation between the ADCs of rectal cancer lesions and their SUVs derived from hybrid PET/MR. Nine patients with histologically proven rectal adenocarcinoma (5 men, 4 women; mean age, 70 ± 15.91 years) underwent torso {sup 18}F-FDG PET/CT and regional hybrid {sup 18}F-FDG PET/MR sequentially. A fixed threshold value of 40 % of maximum uptake was used to determine tumor volume of interest (VOI) on PET image; SUV{sub max}, SUV{sub peak}, and SUV{sub mean} were calculated automatically. A single freehand region of interest (ROI) was drawn on high b-value (b1000) DWI image and copied to corresponding ADC map to determine the ADCmean of rectal cancer lesion. Spearman'rank correlation coefficient (ρ) was calculated to determine the correlation between SUVs and ADC values. SUV{sub max}, SUV{sub peak}, and SUV{sub mean} derived by hybrid PET/MR were 12.35 ± 4.66 (mean ± standard deviation), 9.66  ± 3.15 and 7.41 ± 2.54, respectively. The ADCmean value of rectal cancer lesions was 1.02 ± 0.08 × 10{sup -3}mm{sup 2}/s. ADCmean was significantly and inversely correlated with SUV values (SUV{sub max}, ρ = -0.95, p < 0.001; SUV{sub peak}, ρ = -0.93, p < 0.001; SUV{sub mean}, ρ = -0.91, p = 0.001). This preliminary hybrid PET/MR study demonstrates a significant inverse correlation exists between metabolic activity on {sup 18}F-FDG PET and water diffusion on DWI in rectal cancer.

  6. Impact of exact exchange in the description of the electronic structure of organic charge-transfer molecular crystals

    KAUST Repository

    Fonari, Alexandr

    2014-10-21

    We evaluate the impact that the amount of nonlocal Hartree-Fock (%HF) exchange included in a hybrid density functional has on the microscopic parameters (transfer integrals, band gaps, bandwidths, and effective masses) describing charge transport in high-mobility organic crystals. We consider both crystals based on a single molecule, such as pentacene, and crystals based on mixed-stack charge-transfer systems, such as dibenzo-TTF–TCNQ. In the pentacene crystal, the band gap decreases and the effective masses increase linearly with an increase in the amount of %HF exchange. In contrast, in the charge-transfer crystals, while the band gap increases linearly, the effective masses vary only slightly with an increase in %HF exchange. We show that the superexchange nature of the electronic couplings in charge-transfer systems is responsible for this peculiar evolution of the effective masses. We compare the density functional theory results with results obtained within the G0W0 approximation as a way of benchmarking the optimal amount of %HF exchange needed in a given functional.

  7. Optimal design of the first stage of the plate-fin heat exchanger for the EAST cryogenic system

    Science.gov (United States)

    Qingfeng, JIANG; Zhigang, ZHU; Qiyong, ZHANG; Ming, ZHUANG; Xiaofei, LU

    2018-03-01

    The size of the heat exchanger is an important factor determining the dimensions of the cold box in helium cryogenic systems. In this paper, a counter-flow multi-stream plate-fin heat exchanger is optimized by means of a spatial interpolation method coupled with a hybrid genetic algorithm. Compared with empirical correlations, this spatial interpolation algorithm based on a kriging model can be adopted to more precisely predict the Colburn heat transfer factors and Fanning friction factors of offset-strip fins. Moreover, strict computational fluid dynamics simulations can be carried out to predict the heat transfer and friction performance in the absence of reliable experimental data. Within the constraints of heat exchange requirements, maximum allowable pressure drop, existing manufacturing techniques and structural strength, a mathematical model of an optimized design with discrete and continuous variables based on a hybrid genetic algorithm is established in order to minimize the volume. The results show that for the first-stage heat exchanger in the EAST refrigerator, the structural size could be decreased from the original 2.200 × 0.600 × 0.627 (m3) to the optimized 1.854 × 0.420 × 0.340 (m3), with a large reduction in volume. The current work demonstrates that the proposed method could be a useful tool to achieve optimization in an actual engineering project during the practical design process.

  8. The effect of additional equilibrium stress functions on the three-node hybrid-mixed curved beam element

    International Nuclear Information System (INIS)

    Kim, Jin Gon; Park, Yong Kuk

    2008-01-01

    To develop an effective hybrid-mixed element, it is extremely critical as to how to assume the stress field. This research article demonstrates the effect of additional equilibrium stress functions to enhance the numerical performance of the locking-free three-node hybrid-mixed curved beam element, proposed in Saleeb and Chang's previous work. It is exceedingly complicated or even infeasible to determine the stress functions to satisfy fully both the equilibrium conditions and suppression of kinematic deformation modes in the three-node hybrid-mixed formulation. Accordingly, the additional stress functions to satisfy partially or fully equilibrium conditions are incorporated in this study. Several numerical examples for static and dynamic problems confirm that the newly proposed element with these additional stress functions is highly effective regardless of the slenderness ratio and curvature of arches in static and dynamic analyses

  9. Two-point correlation functions in inhomogeneous and anisotropic cosmologies

    International Nuclear Information System (INIS)

    Marcori, Oton H.; Pereira, Thiago S.

    2017-01-01

    Two-point correlation functions are ubiquitous tools of modern cosmology, appearing in disparate topics ranging from cosmological inflation to late-time astrophysics. When the background spacetime is maximally symmetric, invariance arguments can be used to fix the functional dependence of this function as the invariant distance between any two points. In this paper we introduce a novel formalism which fixes this functional dependence directly from the isometries of the background metric, thus allowing one to quickly assess the overall features of Gaussian correlators without resorting to the full machinery of perturbation theory. As an application we construct the CMB temperature correlation function in one inhomogeneous (namely, an off-center LTB model) and two spatially flat and anisotropic (Bianchi) universes, and derive their covariance matrices in the limit of almost Friedmannian symmetry. We show how the method can be extended to arbitrary N -point correlation functions and illustrate its use by constructing three-point correlation functions in some simple geometries.

  10. Two-point correlation functions in inhomogeneous and anisotropic cosmologies

    Energy Technology Data Exchange (ETDEWEB)

    Marcori, Oton H.; Pereira, Thiago S., E-mail: otonhm@hotmail.com, E-mail: tspereira@uel.br [Departamento de Física, Universidade Estadual de Londrina, 86057-970, Londrina PR (Brazil)

    2017-02-01

    Two-point correlation functions are ubiquitous tools of modern cosmology, appearing in disparate topics ranging from cosmological inflation to late-time astrophysics. When the background spacetime is maximally symmetric, invariance arguments can be used to fix the functional dependence of this function as the invariant distance between any two points. In this paper we introduce a novel formalism which fixes this functional dependence directly from the isometries of the background metric, thus allowing one to quickly assess the overall features of Gaussian correlators without resorting to the full machinery of perturbation theory. As an application we construct the CMB temperature correlation function in one inhomogeneous (namely, an off-center LTB model) and two spatially flat and anisotropic (Bianchi) universes, and derive their covariance matrices in the limit of almost Friedmannian symmetry. We show how the method can be extended to arbitrary N -point correlation functions and illustrate its use by constructing three-point correlation functions in some simple geometries.

  11. Effect of correlation on the band structure of α-cerium

    International Nuclear Information System (INIS)

    Rao, R.S.; Singh, R.P.

    1975-01-01

    The electronic band structure of f.c.c. phase of the rare earth metal cerium (α-cerium) has been calculated using a formulation of the crystal potential where correlation also has been included in addition to exchange. The Green's function method of Korringa-Kohn and Rostoker has been used due to obvious advantages in calculation. The calculations indicate that the s-d bands are hybridized with the f-levels but the f-bands are fairly narrow and lie slightly above the Fermi level. The structure of the bands is qualitatively similar to those of calculations by others except for a general shift of the entire set of bands by about 0.1 Ryd. Thd density of states has also been calculated from the bands obtained. The spin susceptibility of α-cerium has also been calculated using the Kohn-Sham method. However, the calculated additional contributions to the band structure values cannot still explain the large experimental values reported in the literature. (author)

  12. Multi-functional quantum router using hybrid opto-electromechanics

    Science.gov (United States)

    Ma, Peng-Cheng; Yan, Lei-Lei; Chen, Gui-Bin; Li, Xiao-Wei; Liu, Shu-Jing; Zhan, You-Bang

    2018-03-01

    Quantum routers engineered with multiple frequency bands play a key role in quantum networks. We propose an experimentally accessible scheme for a multi-functional quantum router, using photon-phonon conversion in a hybrid opto-electromechanical system. Our proposed device functions as a bidirectional, tunable multi-channel quantum router, and demonstrates the possibility to route single optical photons bidirectionally and simultaneously to three different output ports, by adjusting the microwave power. Further, the device also behaves as an interswitching unit for microwave and optical photons, yielding probabilistic routing of microwave (optical) signals to optical (microwave) outports. With respect to potential application, we verify the insignificant influence from vacuum and thermal noises in the performance of the router under cryogenic conditions.

  13. Functional Abstraction of Stochastic Hybrid Systems

    NARCIS (Netherlands)

    Bujorianu, L.M.; Blom, Henk A.P.; Hermanns, H.

    2006-01-01

    The verification problem for stochastic hybrid systems is quite difficult. One method to verify these systems is stochastic reachability analysis. Concepts of abstractions for stochastic hybrid systems are needed to ease the stochastic reachability analysis. In this paper, we set up different ways

  14. Development of Latent Fingermarks on Nonporous and Semiporous Substrates Using Photoluminescent Eu(Phen)2 Complex Intercalated Clay Hybrids with Enhanced Adhesion.

    Science.gov (United States)

    Kim, Aran; Ryu, Seung-Jin; Lee, Jihye; Jung, Hyun

    2018-03-01

    In forensic science, developing latent fingermarks using powders is a critical, general method to identify individuals. Photoluminescent Eu(Phen) 2 complex intercalated clay hybrids have been used to improve the visualization of fingermarks on nonporous (glass and polymer film) and semiporous (euro and dollar banknotes) substrates. An ion exchange reaction has been successfully used to intercalate Eu(Phen) 2 complex ions into the interlayer spacing of two different Na + -clays, Na + -montmorillonite and Na + -hectorite, with different primary particle sizes. To change the surface properties of the obtained hybrid to be more lipophilic, the hydroxyl groups at the edge of the hectorite hybrid were modified with hexadecyltrimethoxysilane via silylation. We investigated the correlation of the size and surface properties of the hybrids with their adhesion to fingermark residues. Fingermarks were successfully visualized using hybrids under UV illumination. In particular, ridge details on semiporous substrates can be more clearly seen using hybrids with smaller primary particles and greater lipophilicity. © 2018 American Academy of Forensic Sciences.

  15. Turn exchange rhythm in English dialogues

    Science.gov (United States)

    Fon, Janice

    2005-09-01

    This study looked at the relationship between rhythm and exchange type in British English, a stress-timed language, and Singaporean English, a syllable-timed language, using a spontaneous speech corpus. Exchange intervals (EIs), or the time difference between the end of one speaker and the beginning of another, were measured and exchanges of different types were labeled. Results showed that, in a dialogue, EIs were generally limited to a narrow range. However, within this range, EIs had at least four functions. First, EIs were reflective of the cognitive load and functioned as a way to differentiate various exchange types. Those requiring more cognitive resources, such as question-and-answer pairs, generally needed longer EIs than those not as cognitively loaded, such as backchanneling pairs. Second, EIs were indicative of linguistic rhythm. Singaporean English tended to have shorter EIs than British English. Third, EIs were reflective of politeness. The degree of politeness correlated negatively with EI. Shorter EIs showed a higher degree of respect. Finally, EIs were also indicative of the level of insecurity of a speaker, which was best reflected by gender differences. Females in general had longer EIs than males.

  16. Carbon X-ray absorption spectra of fluoroethenes and acetone: a study at the coupled cluster, density functional, and static-exchange levels of theory.

    Science.gov (United States)

    Fransson, Thomas; Coriani, Sonia; Christiansen, Ove; Norman, Patrick

    2013-03-28

    Near carbon K-edge X-ray absorption fine structure spectra of a series of fluorine-substituted ethenes and acetone have been studied using coupled cluster and density functional theory (DFT) polarization propagator methods, as well as the static-exchange (STEX) approach. With the complex polarization propagator (CPP) implemented in coupled cluster theory, relaxation effects following the excitation of core electrons are accounted for in terms of electron correlation, enabling a systematic convergence of these effects with respect to electron excitations in the cluster operator. Coupled cluster results have been used as benchmarks for the assessment of propagator methods in DFT as well as the state-specific static-exchange approach. Calculations on ethene and 1,1-difluoroethene illustrate the possibility of using nonrelativistic coupled cluster singles and doubles (CCSD) with additional effects of electron correlation and relativity added as scalar shifts in energetics. It has been demonstrated that CPP spectra obtained with coupled cluster singles and approximate doubles (CC2), CCSD, and DFT (with a Coulomb attenuated exchange-correlation functional) yield excellent predictions of chemical shifts for vinylfluoride, 1,1-difluoroethene, trifluoroethene, as well as good spectral features for acetone in the case of CCSD and DFT. Following this, CPP-DFT is considered to be a viable option for the calculation of X-ray absorption spectra of larger π-conjugated systems, and CC2 is deemed applicable for chemical shifts but not for studies of fine structure features. The CCSD method as well as the more approximate CC2 method are shown to yield spectral features relating to π∗-resonances in good agreement with experiment, not only for the aforementioned molecules but also for ethene, cis-1,2-difluoroethene, and tetrafluoroethene. The STEX approach is shown to underestimate π∗-peak separations due to spectral compressions, a characteristic which is inherent to this

  17. Exchange Rate and Interest Rate in the Monetary Policy Reaction Function

    Directory of Open Access Journals (Sweden)

    Krušković Borivoje D.

    2017-01-01

    Full Text Available In recent years there has been a particular interest in the relation between exchange rates and interest rates both in developed countries and emerging countries. This is understandable given the important role that these variables have in determining the movement of nominal and real economic variables, including the movement of domestic inflation, real output, exports and imports, foreign exchange reserves, etc. To realized the importance of the given instruments selected macroeconomic indicators, data analysis (monthly data relating to Serbia was made on the basis of the Transfer Function Model, a data analysis (annual data relating to emerging countries was done on the basis of the Stepvise Multiple Regression model. In the transfer function model we used the Maximum Likelihood method for assessing unknown coefficients. In the gradual multiple regression model we used the Least Square method for the evaluation of unknown coefficients. All indicator values were used in the original unmodified form, i.e. there was no need for a variety of transformations. Empirical analysis showed that the exchange rate is a more significant transmission mechanism than the interest rate both in emerging markets and Serbia.

  18. The use of perturbation theory in density-functional theory

    International Nuclear Information System (INIS)

    Goerling, A.

    1996-01-01

    Perturbation theory with respect to the electron-electron interaction leads to expressions for the exchange and correlation energies and potentials in terms of Kohn-Sham orbitals and Kohn-Sham eigenvalues. An exact open-quote exchange-only close-quote procedure for solids is introduced. Results for several semiconductors are presented. Perturbation theory expansions for the hardness of molecules and the bad gap of solids are given. Density-functional exchange and correlation energies for excited states are defined and a perturbation theory based Kohn-Sham formalism to treat excited states within density-functional theory is introduced

  19. A-centers in silicon studied with hybrid density functional theory

    KAUST Repository

    Wang, Hao; Chroneos, Alexander; Londos, C. A.; Schwingenschlö gl, Udo; Sgourou, E. N.

    2013-01-01

    Density functional theory employing hybrid functional is used to gain fundamental insight into the interaction of vacancies with oxygen interstitials to form defects known as A-centers in silicon. We calculate the formation energy of the defect with respect to the Fermi energy for all possible charge states. It is found that the neutral and doubly negatively charged A-centers dominate. The findings are analyzed in terms of the density of states and discussed in view of previous experimental and theoretical studies.

  20. A-centers in silicon studied with hybrid density functional theory

    KAUST Repository

    Wang, Hao

    2013-07-29

    Density functional theory employing hybrid functional is used to gain fundamental insight into the interaction of vacancies with oxygen interstitials to form defects known as A-centers in silicon. We calculate the formation energy of the defect with respect to the Fermi energy for all possible charge states. It is found that the neutral and doubly negatively charged A-centers dominate. The findings are analyzed in terms of the density of states and discussed in view of previous experimental and theoretical studies.

  1. İşletmelerde Bir Avantaj Unsuru Olarak Kur Korelasyonlarının Kullanımı(Using Exchange Rate Correlation as An Advantage Factor in Managements

    Directory of Open Access Journals (Sweden)

    Cantürk KAYAHAN

    2008-01-01

    Full Text Available Today, international competition is not only based on production of technology and product, but also requires use of some financial advantages. Exchange rate correlations one of these advantages allow the financial managers to understand how exchange rates change and to follow portfolio risks better. Some exchange rates may change the same way, while the others may change opposite way. In this study, the effect of exchange rate correlations over a sample portfolio is analyzed and their possible advantages or disadvantages over firms are evaluated.

  2. Two-point correlation function for Dirichlet L-functions

    Science.gov (United States)

    Bogomolny, E.; Keating, J. P.

    2013-03-01

    The two-point correlation function for the zeros of Dirichlet L-functions at a height E on the critical line is calculated heuristically using a generalization of the Hardy-Littlewood conjecture for pairs of primes in arithmetic progression. The result matches the conjectured random-matrix form in the limit as E → ∞ and, importantly, includes finite-E corrections. These finite-E corrections differ from those in the case of the Riemann zeta-function, obtained in Bogomolny and Keating (1996 Phys. Rev. Lett. 77 1472), by certain finite products of primes which divide the modulus of the primitive character used to construct the L-function in question.

  3. Two-point correlation function for Dirichlet L-functions

    International Nuclear Information System (INIS)

    Bogomolny, E; Keating, J P

    2013-01-01

    The two-point correlation function for the zeros of Dirichlet L-functions at a height E on the critical line is calculated heuristically using a generalization of the Hardy–Littlewood conjecture for pairs of primes in arithmetic progression. The result matches the conjectured random-matrix form in the limit as E → ∞ and, importantly, includes finite-E corrections. These finite-E corrections differ from those in the case of the Riemann zeta-function, obtained in Bogomolny and Keating (1996 Phys. Rev. Lett. 77 1472), by certain finite products of primes which divide the modulus of the primitive character used to construct the L-function in question. (paper)

  4. Development and testing of a hybrid system with a sub-kW open-cathode type PEM (proton exchange membrane) fuel cell stack

    International Nuclear Information System (INIS)

    Huang, Zhen-Ming; Su, Ay; Liu, Ying-Chieh

    2014-01-01

    In this study, the performance of a polymer electrolyte membrane fuel cell stack has been evaluated for a hybrid power system test platform. To simulate vehicle acceleration, the stack was operated under dynamic-loading, and to demonstrate the exchange of power flow between two power sources the hybrid power system was tested under three different modes. A unit cell was fabricated for high stack performance and the stack was constructed with 18 open-cathode type fuel cells. Air which acts as a coolant as well as an oxidant for electrochemical reactions is provided by a pair of fans. The capabilities of the stack for hybrid power system test platform were validated by successful dynamic-loading tests. The performance of the stack for various air fan voltage was evaluated and an optimal value was concluded. The conditions like inlet temperature of H 2 and the stack current were established for maximum power. It was also found that humidification of hydrogen at anode inlet degrades the stack performance and stability due to flooding. Evidence shows that for the higher overall performance, the fuel cell acts continuously on constant current output. The study contributes to the design of mobility hybrid system to get better performance and reliability. - Highlights: • An open-cathode type PEMFC (polymer electrolyte membrane fuel cell) stack (rated output 300 W) was fabricated. • The open-cathode configuration simplifies the design of a stack system. • Assess the feasibility of combining a fuel cell stack in a hybrid system. • The study contributes to the design of mobility hybrid system to get better performance and reliability

  5. Improved performance of colloidal CdSe quantum dot-sensitized solar cells by hybrid passivation.

    Science.gov (United States)

    Huang, Jing; Xu, Bo; Yuan, Chunze; Chen, Hong; Sun, Junliang; Sun, Licheng; Agren, Hans

    2014-11-12

    A hybrid passivation strategy is employed to modify the surface of colloidal CdSe quantum dots (QDs) for quantum dot-sensitized solar cells (QDSCs), by using mercaptopropionic acid (MPA) and iodide anions through a ligand exchange reaction in solution. This is found to be an effective way to improve the performance of QDSCs based on colloidal QDs. The results show that MPA can increase the coverage of the QDs on TiO2 electrodes and facilitate the hole extraction from the photoxidized QDs, and simultaneously, that the iodide anions can remedy the surface defects of the CdSe QDs and thus reduce the recombination loss in the device. This hybrid passivation treatment leads to a significant enhancement of the power conversion efficiency of the QDSCs by 41%. Furthermore, an optimal ratio of iodide ions to MPA was determined for favorable hybrid passivation; results show that excessive iodine anions are detrimental to the loading of the QDs. This study demonstrates that the improvement in QDSC performance can be realized by using a combination of different functional ligands to passivate the QDs, and that ligand exchange in solution can be an effective approach to introduce different ligands.

  6. Hybridization interactions between probesets in short oligo microarrays lead to spurious correlations

    Directory of Open Access Journals (Sweden)

    Miller Crispin J

    2006-06-01

    Full Text Available Abstract Background Microarrays measure the binding of nucleotide sequences to a set of sequence specific probes. This information is combined with annotation specifying the relationship between probes and targets and used to make inferences about transcript- and, ultimately, gene expression. In some situations, a probe is capable of hybridizing to more than one transcript, in others, multiple probes can target a single sequence. These 'multiply targeted' probes can result in non-independence between measured expression levels. Results An analysis of these relationships for Affymetrix arrays considered both the extent and influence of exact matches between probe and transcript sequences. For the popular HGU133A array, approximately half of the probesets were found to interact in this way. Both real and simulated expression datasets were used to examine how these effects influenced the expression signal. It was found not only to lead to increased signal strength for the affected probesets, but the major effect is to significantly increase their correlation, even in situations when only a single probe from a probeset was involved. By building a network of probe-probeset-transcript relationships, it is possible to identify families of interacting probesets. More than 10% of the families contain members annotated to different genes or even different Unigene clusters. Within a family, a mixture of genuine biological and artefactual correlations can occur. Conclusion Multiple targeting is not only prevalent, but also significant. The ability of probesets to hybridize to more than one gene product can lead to false positives when analysing gene expression. Comprehensive annotation describing multiple targeting is required when interpreting array data.

  7. A Dynamic Multistage Hybrid Swarm Intelligence Optimization Algorithm for Function Optimization

    Directory of Open Access Journals (Sweden)

    Daqing Wu

    2012-01-01

    Full Text Available A novel dynamic multistage hybrid swarm intelligence optimization algorithm is introduced, which is abbreviated as DM-PSO-ABC. The DM-PSO-ABC combined the exploration capabilities of the dynamic multiswarm particle swarm optimizer (PSO and the stochastic exploitation of the cooperative artificial bee colony algorithm (CABC for solving the function optimization. In the proposed hybrid algorithm, the whole process is divided into three stages. In the first stage, a dynamic multiswarm PSO is constructed to maintain the population diversity. In the second stage, the parallel, positive feedback of CABC was implemented in each small swarm. In the third stage, we make use of the particle swarm optimization global model, which has a faster convergence speed to enhance the global convergence in solving the whole problem. To verify the effectiveness and efficiency of the proposed hybrid algorithm, various scale benchmark problems are tested to demonstrate the potential of the proposed multistage hybrid swarm intelligence optimization algorithm. The results show that DM-PSO-ABC is better in the search precision, and convergence property and has strong ability to escape from the local suboptima when compared with several other peer algorithms.

  8. Four-Component Relativistic Density-Functional Theory Calculations of Nuclear Spin-Rotation Constants: Relativistic Effects in p-Block Hydrides.

    Science.gov (United States)

    Komorovsky, Stanislav; Repisky, Michal; Malkin, Elena; Demissie, Taye B; Ruud, Kenneth

    2015-08-11

    We present an implementation of the nuclear spin-rotation (SR) constants based on the relativistic four-component Dirac-Coulomb Hamiltonian. This formalism has been implemented in the framework of the Hartree-Fock and Kohn-Sham theory, allowing assessment of both pure and hybrid exchange-correlation functionals. In the density-functional theory (DFT) implementation of the response equations, a noncollinear generalized gradient approximation (GGA) has been used. The present approach enforces a restricted kinetic balance condition for the small-component basis at the integral level, leading to very efficient calculations of the property. We apply the methodology to study relativistic effects on the spin-rotation constants by performing calculations on XHn (n = 1-4) for all elements X in the p-block of the periodic table and comparing the effects of relativity on the nuclear SR tensors to that observed for the nuclear magnetic shielding tensors. Correlation effects as described by the density-functional theory are shown to be significant for the spin-rotation constants, whereas the differences between the use of GGA and hybrid density functionals are much smaller. Our calculated relativistic spin-rotation constants at the DFT level of theory are only in fair agreement with available experimental data. It is shown that the scaling of the relativistic effects for the spin-rotation constants (varying between Z(3.8) and Z(4.5)) is as strong as for the chemical shieldings but with a much smaller prefactor.

  9. Exchange coupling interactions in a Fe6 complex: A theoretical study using density functional theory

    International Nuclear Information System (INIS)

    Cauchy, Thomas; Ruiz, Eliseo; Alvarez, Santiago

    2006-01-01

    Theoretical methods based on density functional theory have been employed to analyze the exchange interactions in an Fe 6 complex. The calculated exchange coupling constants are consistent with an S=5 ground state and agree well with those reported previously for other Fe III polynuclear complexes. Ferromagnetic interactions may appear through exchange pathways formed by two bridging hydroxo or oxo ligands

  10. The role of triplet correlation function in dense fluids

    International Nuclear Information System (INIS)

    Rashid, R.I.M.A.

    1993-09-01

    In the theory of dense liquids, one usually introduces various correlation functions for describing properties of such systems. It has proved impossible to solve these correlation functions exactly and as such one often resorts to some meaningful approximations for their solutions. It is well known that unless proper precautions are taken, the approximate solutions will violate some useful sum rules and thermodynamic consistency conditions. Here the general rules for generating thermodynamically consistent approximate correlation functions are discussed. The role of triplet correlation is elucidated further by calculating a residual correction to the vacancy formation energy via three-particle correlation in rare gas solids. (author). 16 refs, 4 figs, 1 tab

  11. Magnetic instability with increasing hybridization in cerium compounds

    International Nuclear Information System (INIS)

    Kioussis, N.; Cooper, B.R.; Wills, J.M.

    1991-01-01

    A synthesis of a phenomenological theory of orbitally driven magnetic ordering of moderately delocalized light rare-earth systems and ab initio electronic structure calculations has been applied to investigate the change in magnetic behavior on going from CeSb to CeTe, both of which have rocksalt structure with a small decrease in lattice parameter. The hybridization-potential matrix elements and the band energies entering the Anderson-lattice Hamiltonian are obtained from linear-muffin-tin-orbital (LMTO) electronic-structure calculations with the Ce 4f states treated as core states. The position of the Ce 4f energy level relative to the Fermi energy and the intra-atomic Coulomb energy U are obtained by use of a sequence of three total-energy supercell calculations with one out of four Ce sites constrained to f n occupation with n=0,1,2, successively. The calculations elucidate the origins, in the electronic structure, of the variation of the f-state resonance width and hybridization potential on going from CeSb to CeTe, and the resultant sensitivity of the hybridization dressing of the crystal-field splitting and the hybridization-induced exchange interactions to chemical environment. The effect of opening up successive angular momentum scattering channels of the ab initio calculated two-ion exchange-interaction matrix on the nature of the magnetic ordering is examined. The calculated magnitude and range dependence of the two-ion exchange interactions changes sharply from CeSb to CeTe, yielding a change in magnetic behavior in qualitative agreement with experiment. The nonlinear hybridization effects on the hybridization dressing of the crystal-field splitting have been examined

  12. Local Descriptors of Dynamic and Nondynamic Correlation.

    Science.gov (United States)

    Ramos-Cordoba, Eloy; Matito, Eduard

    2017-06-13

    Quantitatively accurate electronic structure calculations rely on the proper description of electron correlation. A judicious choice of the approximate quantum chemistry method depends upon the importance of dynamic and nondynamic correlation, which is usually assesed by scalar measures. Existing measures of electron correlation do not consider separately the regions of the Cartesian space where dynamic or nondynamic correlation are most important. We introduce real-space descriptors of dynamic and nondynamic electron correlation that admit orbital decomposition. Integration of the local descriptors yields global numbers that can be used to quantify dynamic and nondynamic correlation. Illustrative examples over different chemical systems with varying electron correlation regimes are used to demonstrate the capabilities of the local descriptors. Since the expressions only require orbitals and occupation numbers, they can be readily applied in the context of local correlation methods, hybrid methods, density matrix functional theory, and fractional-occupancy density functional theory.

  13. New real space correlated-basis-functions approach for the electron correlations of the semiconductor inversion layer

    International Nuclear Information System (INIS)

    Feng Weiguo; Wang Hongwei; Wu Xiang

    1989-12-01

    Based on the real space Correlated-Basis-Functions theory and the collective oscillation behaviour of the electron gas with effective Coulomb interaction, the many body wave function is obtained for the quasi-two-dimensional electron system in the semiconductor inversion layer. The pair-correlation function and the correlation energy of the system have been calculated by the integro-differential method in this paper. The comparison with the other previous theoretical results is also made. The new theoretical approach and its numerical results show that the pair-correlation functions are definitely positive and satisfy the normalization condition. (author). 10 refs, 2 figs

  14. Enzymatic functionalization of cork surface with antimicrobial hybrid biopolymer/silver nanoparticles.

    Science.gov (United States)

    Francesko, Antonio; Blandón, Lucas; Vázquez, Mario; Petkova, Petya; Morató, Jordi; Pfeifer, Annett; Heinze, Thomas; Mendoza, Ernest; Tzanov, Tzanko

    2015-05-13

    Laccase-assisted assembling of hybrid biopolymer-silver nanoparticles and cork matrices into an antimicrobial material with potential for water remediation is herein described. Amino-functional biopolymers were first used as doping agents to stabilize concentrated colloidal dispersions of silver nanoparticles (AgNP), additionally providing the particles with functionalities for covalent immobilization onto cork to impart a durable antibacterial effect. The solvent-free AgNP synthesis by chemical reduction was carried out in the presence of chitosan (CS) or 6-deoxy-6-(ω-aminoethyl) aminocellulose (AC), leading to simultaneous AgNP biofunctionalization. This approach resulted in concentrated hybrid NP dispersion stable to aggregation and with hydrodynamic radius of particles of about 250 nm. Moreover, laccase enabled coupling between the phenolic groups in cork and amino moieties in the biopolymer-doped AgNP for permanent modification of the material. The antibacterial efficiency of the functionalized cork matrices, aimed as adsorbents for wastewater treatment, was evaluated against Escherichia coli and Staphylococcus aureus during 5 days in conditions mimicking those in constructed wetlands. Both intrinsically antimicrobial CS and AC contributed to the bactericidal effect of the enzymatically grafted on cork AgNP. In contrast, unmodified AgNP were easily washed off from the material, confirming that the biopolymers potentiated a durable antibacterial functionalization of the cork matrices.

  15. Comparison of exact-exchange calculations for solids in current-spin-density- and spin-density-functional theory

    DEFF Research Database (Denmark)

    Sharma, S.; Pittalis, S.; Kurth, S.

    2007-01-01

    The relative merits of current-spin-density- and spin-density-functional theory are investigated for solids treated within the exact-exchange-only approximation. Spin-orbit splittings and orbital magnetic moments are determined at zero external magnetic field. We find that for magnetic (Fe, Co......, and Ni) and nonmagnetic (Si and Ge) solids, the exact-exchange current-spin-density functional approach does not significantly improve the accuracy of the corresponding spin-density functional results....

  16. Hybrid artificial bee colony algorithm for parameter optimization of five-parameter bidirectional reflectance distribution function model.

    Science.gov (United States)

    Wang, Qianqian; Zhao, Jing; Gong, Yong; Hao, Qun; Peng, Zhong

    2017-11-20

    A hybrid artificial bee colony (ABC) algorithm inspired by the best-so-far solution and bacterial chemotaxis was introduced to optimize the parameters of the five-parameter bidirectional reflectance distribution function (BRDF) model. To verify the performance of the hybrid ABC algorithm, we measured BRDF of three kinds of samples and simulated the undetermined parameters of the five-parameter BRDF model using the hybrid ABC algorithm and the genetic algorithm, respectively. The experimental results demonstrate that the hybrid ABC algorithm outperforms the genetic algorithm in convergence speed, accuracy, and time efficiency under the same conditions.

  17. Photoconductivity enhancement and charge transport properties in ruthenium-containing block copolymer/carbon nanotube hybrids.

    Science.gov (United States)

    Lo, Kin Cheung; Hau, King In; Chan, Wai Kin

    2018-04-05

    Functional polymer/carbon nanotube (CNT) hybrid materials can serve as a good model for light harvesting systems based on CNTs. This paper presents the synthesis of block copolymer/CNT hybrids and the characterization of their photocurrent responses by both experimental and computational approaches. A series of functional diblock copolymers was synthesized by reversible addition-fragmentation chain transfer polymerizations for the dispersion and functionalization of CNTs. The block copolymers contain photosensitizing ruthenium complexes and modified pyrene-based anchoring units. The photocurrent responses of the polymer/CNT hybrids were measured by photoconductive atomic force microscopy (PCAFM), from which the experimental data were analyzed by vigorous statistical models. The difference in photocurrent response among different hybrids was correlated to the conformations of the hybrids, which were elucidated by molecular dynamics simulations, and the electronic properties of polymers. The photoresponse of the block copolymer/CNT hybrids can be enhanced by introducing an electron-accepting block between the photosensitizing block and the CNT. We have demonstrated that the application of a rigorous statistical methodology can unravel the charge transport properties of these hybrid materials and provide general guidelines for the design of molecular light harvesting systems.

  18. Redshift distortions of galaxy correlation functions

    International Nuclear Information System (INIS)

    Fry, J.N.; Florida Univ., Gainesville, FL; Gaztanaga, E.; Oxford Univ.

    1993-01-01

    To examine how peculiar velocities can affect the 2-, 3-, and 4-point correlation functions, we evaluate volume-average correlations for configurations that emphasize and minimize distortions for four different volume-limited samples from each of the CfA, SSRS, and IRAS redshift catalogs. We present the results as the correlation length r 0 and power index γ of the 2-point correlation, anti Ξ 2 = (r 0 /r) γ , and as the hierarchical amplitudes of the 3- and 4-point functions, S 3 = anti Ξ 3 /anti Ξ 2 2 and S 4 = anti Ξ/anti Ξ 2 3 . We find a characteristic distortion for anti Ξ 2 : The slope γ is flatter and the correlation length is larger in redshift space than in real space; that is, redshift distortions ''move'' correlations from small to large scales. At the largest scales, extra power in the redshift distribution is compatible with Ω 4/7 /b ∼ 1; we find 0.53 ± 0.15, 1.10 ± 0.16 and 0.84 ± 0.45 for the CfA, SSRS and IRAS catalogs. Higher order correlations anti Ξ 3 and anti Ξ 4 suffer similar redshift distortions, but in such a way that, within the accuracy of our analysis, the normalized amplitudes S 3 and S 4 are insensitive to this effect. The hierarchical amplitudes S 3 and S 4 are constant as a function of scale between 1-12 h -1 Mpc and have similar values in all samples and catalogues, S 3 ∼ 2 and S 4 ∼ 6, despite the fact that anti Ξ 2 , anti Ξ 3 , and anti Ξ 4 differ from one sample to another by large factors. The agreement between the independent estimations of S 3 and S 4 is remarkable given the different criteria in the selection of galaxies and also the difference in the resulting range of densities, luminosities and locations between samples

  19. Exchangers man the pumps: Functional interplay between proton pumps and proton-coupled Ca2+ exchangers

    OpenAIRE

    Barkla, Bronwyn J; Hirschi, Kendal D; Pittman, Jon K

    2008-01-01

    Tonoplast-localised proton-coupled Ca2+ transporters encoded by cation/H+ exchanger (CAX) genes play a critical role in sequestering Ca2+ into the vacuole. These transporters may function in coordination with Ca2+ release channels, to shape stimulus-induced cytosolic Ca2+ elevations. Recent analysis of Arabidopsis CAX knockout mutants, particularly cax1 and cax3, identified a variety of phenotypes including sensitivity to abiotic stresses, which indicated that these transporters might play a ...

  20. Thermochemical Storage of Middle Temperature Wasted Heat by Functionalized C/Mg(OH2 Hybrid Materials

    Directory of Open Access Journals (Sweden)

    Emanuela Mastronardo

    2017-01-01

    Full Text Available For the thermochemical performance implementation of Mg(OH2 as a heat storage medium, several hybrid materials have been investigated. For this study, high-performance hybrid materials have been developed by exploiting the authors’ previous findings. Expanded graphite (EG/carbon nanotubes (CNTs-Mg(OH2 hybrid materials have been prepared through Mg(OH2 deposition-precipitation over functionalized, i.e., oxidized, or un-functionalized EG or CNTs. The heat storage performances of the carbon-based hybrid materials have been investigated through a laboratory-scale experimental simulation of the heat storage/release cycles, carried out by a thermogravimetric apparatus. This study offers a critical evaluation of the thermochemical performances of developed materials through their comparison in terms of heat storage and output capacities per mass and volume unit. It was demonstrated that both EG and CNTs improves the thermochemical performances of the storage medium in terms of reaction rate and conversion with respect to pure Mg(OH2. With functionalized EG/CNTs-Mg(OH2, (i the potential heat storage and output capacities per mass unit of Mg(OH2 have been completely exploited; and (ii higher heat storage and output capacities per volume unit were obtained. That means, for technological applications, as smaller volume at equal stored/released heat.

  1. Investigating the effects of heat exchanger on flame transfer function in a simplified boiler

    NARCIS (Netherlands)

    Hosseini, N.; Kornilov, V.N.; Teerling, O. J.; Lopez Arteaga, I.; de Goey, Ph.

    2015-01-01

    The goal of the present work is to investigate the effects the heat exchanger can have on the acoustic response of the flames(flame transfer function) in a boiler. In compact condensing boilers the distance between the burner and heat exchanger is small enough to cause intense interactions. That is

  2. Hybrid inorganic-organic adsorbents Part 1: Synthesis and characterization of mesoporous zirconium titanate frameworks containing coordinating organic functionalities.

    Science.gov (United States)

    Griffith, Christopher S; De Los Reyes, Massey; Scales, Nicholas; Hanna, John V; Luca, Vittorio

    2010-12-01

    A series of functional hybrid inorganic-organic adsorbent materials have been prepared through postsynthetic grafting of mesoporous zirconium titanate xerogel powders using a range of synthesized and commercial mono-, bis-, and tris-phosphonic acids, many of which have never before been investigated for the preparation of hybrid phases. The hybrid materials have been characterized using thermogravimetric analysis, diffuse reflectance infrared (DRIFT) and 31P MAS NMR spectroscopic techniques and their adsorption properties studied using a 153Gd radiotracer. The highest level of surface functionalization (molecules/nm2) was observed for methylphosphonic acid (∼3 molecules/nm2). The level of functionalization decreased with an increase in the number of potential surface coordinating groups of the phosphonic acids. Spectral decomposition of the DRIFT and 31P MAS NMR spectra showed that each of the phosphonic acid molecules coordinated strongly to the metal oxide surface but that for the 1,1-bis-phosphonic acids and tris-phosphonic acids the coordination was highly variable resulting in a proportion of free or loosely coordinated phosphonic acid groups. Functionalization of a porous mixed metal oxide framework with the tris-methylenephosphonic acid (ATMP-ZrTi-0.33) resulted in a hybrid with the highest affinity for 153Gd3+ in nitric acid solutions across a wide range of acid concentrations. The ATMP-ZrTi-0.33 hybrid material extracted 153Gd3+ with a Kd value of 1×10(4) in 0.01 M HNO3 far exceeding that of the other hybrid phases. The unfunctionalized mesoporous mixed metal oxide had negligible affinity for Gd3+ (KdATMP-ZrTi-0.33 hybrid phase for Gd3+ has been determined to be about 0.005 mmol/g in 0.01 M HNO3. This behavior and that of the other hybrid phases suggests that the surface-bound ATMP ligand functions as a chelating ligand toward 153Gd3+ under these acidic conditions.

  3. A novel hybrid chaotic ant swarm algorithm for heat exchanger networks synthesis

    International Nuclear Information System (INIS)

    Zhang, Chunwei; Cui, Guomin; Peng, Fuyu

    2016-01-01

    Highlights: • The chaotic ant swarm algorithm is proposed to avoid trapping into a local optimum. • The organization variables update strategy makes full use of advantages of the chaotic search. • The structure evolution strategy is developed to handle integer variables optimization. • Overall three cases taken form the literatures are investigated with better optima. - Abstract: The heat exchanger networks synthesis (HENS) still remains an open problem due to its combinatorial nature, which can easily result in suboptimal design and unacceptable calculation effort. In this paper, a novel hybrid chaotic ant swarm algorithm is proposed. The presented algorithm, which consists of a combination of chaotic ant swarm (CAS) algorithm, structure evolution strategy, local optimization strategy and organization variables update strategy, can simultaneously optimize continuous variables and integer variables. The CAS algorithm chaotically searches and generates new solutions in the given space, and subsequently the structure evolution strategy evolves the structures represented by the solutions and limits the search space. Furthermore, the local optimizing strategy and the organization variables update strategy are introduced to enhance the performance of the algorithm. The study of three different cases, found in the literature, revealed special search abilities in both structure space and continuous variable space.

  4. Photoionization of Xe inside C60: Atom-fullerene hybridization, giant cross-section enhancement, and correlation confinement resonances

    International Nuclear Information System (INIS)

    Madjet, Mohamed E.; Renger, Thomas; Hopper, Dale E.; McCune, Matthew A.; Chakraborty, Himadri S.; Rost, Jan-M.; Manson, Steven T.

    2010-01-01

    A theoretical study of the subshell photoionization of the Xe atom endohedrally confined in C 60 is presented. Powerful hybridization of the Xe 5s state with the bottom edge of C 60 π band is found that induces strong structures in the 5s ionization, causing the cross section to differ significantly from earlier results that omit this hybridization. The hybridization also affects the angular distribution asymmetry parameter of Xe 5p ionization near the Cooper minimum. The 5p cross section, on the other hand, is greatly enhanced by borrowing considerable oscillator strength from the C 60 giant plasmon resonance via the atom-fullerene dynamical interchannel coupling. Beyond the C 60 plasmon energy range the atomic subshell cross sections display confinement-induced oscillations in which, over the large 4d shape resonance region, the dominant 4d oscillations induce their ''clones'' in all degenerate weaker channels known as correlation confinement resonances.

  5. Can Unrestricted Density-Functional Theory Describe Open Shell Singlet Biradicals?

    Directory of Open Access Journals (Sweden)

    Dieter Cremer

    2002-04-01

    Full Text Available Abstract: Unrestricted density functional theory (UDFT can be used for the description of open-shell singlet (OSS biradicals provided a number of precautions are considered. Biradicals that require a two-determinantal wave function (e.g. OSS state of carbenes cannot be described by UDFT for principal reasons. However, if the overlap between the open-shell orbitals is small (the single electrons are located at different atomic centers errors become small and, then, the principal failure of UDFT in these cases is not apparent and may even be disguised by the fact that UDFT has the advantage of describing spin polarization better than any restricted open shell DFT method. In the case of OSS biradicals with two- or multiconfigurational character (but a onedeterminantal form of the leading configuration, reasonable results can be obtained by broken-symmetry (BS-UDFT, however in each case this has to be checked. In no case is it reasonable to lower the symmetry of a molecule to get a suitable UDFT description. Hybrid functionals such as B3LYP perform better than pure DFT functionals in BS-UDFT calculations because the former reduce the self-interaction error of DFT exchange functionals, which mimics unspecified static electron correlation effects, so that the inclusion of specific static electron correlation effects via the form of the wavefunction becomes more effective.

  6. Excited-state density functional theory

    International Nuclear Information System (INIS)

    Harbola, Manoj K; Hemanadhan, M; Shamim, Md; Samal, P

    2012-01-01

    Starting with a brief introduction to excited-state density functional theory, we present our method of constructing modified local density approximated (MLDA) energy functionals for the excited states. We show that these functionals give accurate results for kinetic energy and exchange energy compared to the ground state LDA functionals. Further, with the inclusion of GGA correction, highly accurate total energies for excited states are obtained. We conclude with a brief discussion on the further direction of research that include the construction of correlation energy functional and exchange potential for excited states.

  7. Hybrid functional band gap calculation of SnO6 containing perovskites and their derived structures

    International Nuclear Information System (INIS)

    Lee, Hyewon; Cheong, S.W.; Kim, Bog G.

    2015-01-01

    We have studied the properties of SnO 6 octahedra-containing perovskites and their derived structures using ab initio calculations with different density functionals. In order to predict the correct band gap of the materials, we have used B3LYP hybrid density functional, and the results of B3LYP were compared with those obtained using the local density approximation and generalized gradient approximation data. The calculations have been conducted for the orthorhombic ground state of the SnO 6 containing perovskites. We also have expended the hybrid density functional calculation to the ASnO 3 /A'SnO 3 system with different cation orderings. We propose an empirical relationship between the tolerance factor and the band gap of SnO 6 containing oxide materials based on first principles calculation. - Graphical abstract: (a) Structure of ASnO 3 for orthorhombic ground state. The green ball is A (Ba, Sr, Ca) cation and the small (red) ball on edge is oxygen. SnO 6 octahedrons are plotted as polyhedron. (b) Band gap of ASnO 3 as a function of the tolerance factor for different density functionals. The experimental values of the band gap are marked as green pentagons. (c) ASnO 3 /A'SnO 3 superlattices with two types cation arrangement: [001] layered structure and [111] rocksalt structure, respectively. (d) B3LYP hybrid functional band gaps of ASnO 3 , [001] ordered superlattices, and [111] ordered superlattices of ASnO 3 /A'SnO 3 as a function of the effective tolerance factor. Note the empirical linear relationship between the band gap and effective tolerance factor. - Highlights: • We report the hybrid functional band gap calculation of ASnO 3 and ASnO 3 /A'SnO 3 . • The band gap of ASnO 3 using B3LYP functional reproduces the experimental value. • We propose the linear relationship between the tolerance factor and the band gap

  8. Synthesis of boronate-functionalized organic-inorganic hybrid monolithic column for the separation of cis-diol containing compounds at low pH.

    Science.gov (United States)

    Zhao, Heqing; Lyu, Haixia; Qin, Wenfei; Xie, Zenghong

    2018-04-01

    In this work, an organic-inorganic hybrid boronate affinity monolithic column was prepared via "one-pot" process using 4-vinylphenylboronic acid as organic monomer and divinylbenzene as cross-linker. The effects of reaction temperature, solvents and composition of organic monomers on the column properties (e.g. morphology, permeability, and mechanical stability) were investigated. A series of test compounds including small neutral molecules, aromatic amines, and cis-diol compounds were used to evaluate the retention behaviors of the prepared hybrid monolithic column. The results demonstrated that the prepared hybrid monolith exhibited mixed-interactions including hydrophilicity, cation exchange, and boronate affinity interaction. The run-to-run, day-to-day and batch-to-batch reproducibilities of the prepared hybrid monolith for thiourea's retention time were satisfactory with the relative standard deviations (RSDs) less than 0.09, 1.45 and 4.05% (n = 3), respectively, indicating the effectiveness and practicability of the proposed method. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Towards hybrid biocompatible magnetic rHuman serum albumin-based nanoparticles: use of ultra-small (CeLn)3/4+ cation-doped maghemite nanoparticles as functional shell

    Science.gov (United States)

    Israel, Liron L.; Kovalenko, Elena I.; Boyko, Anna A.; Sapozhnikov, Alexander M.; Rosenberger, Ina; Kreuter, Jörg; Passoni, Lorena; Lellouche, Jean-Paul

    2015-01-01

    Human serum albumin (HSA) is a protein found in human blood. Over the last decade, HSA has been evaluated as a promising drug carrier. However, not being magnetic, HSA cannot be used for biomedical applications such as magnetic resonance imaging (MRI) and magnetic drug targeting. Therefore, subsequent composites building on iron oxide nanoparticles that are already used clinically as MRI contrast agents are extensively studied. Recently and in this context, innovative fully hydrophilic ultra-small CAN-stabilized maghemite ((CeLn)3/4+-γ-Fe2O3) nanoparticles have been readily fabricated. The present study discusses the design, fabrication, and characterization of a dual phase hybrid core (rHSA)-shell ((CeLn)3/4+-γ-Fe2O3 NPs) nanosystem. Quite importantly and in contrast to widely used encapsulation strategies, rHSA NP surface-attached (CeLn)3/4+-γ-Fe2O3 NPs enabled to exploit both rHSA (protein functionalities) and (CeLn)3/4+-γ-Fe2O3 NP surface functionalities (COOH and ligand L coordinative exchange) in addition to very effective MRI contrast capability due to optimal accessibility of H2O molecules with the outer magnetic phase. Resulting hybrid nanoparticles might be used as a platform modular system for therapeutic (drug delivery system) and MR diagnostic purposes.

  10. Genome-wide dissection of hybrid sterility in Drosophila confirms a polygenic threshold architecture.

    Science.gov (United States)

    Morán, Tomás; Fontdevila, Antonio

    2014-01-01

    To date, different studies about the genetic basis of hybrid male sterility (HMS), a postzygotic reproductive barrier thoroughly investigated using Drosophila species, have demonstrated that no single major gene can produce hybrid sterility without the cooperation of several genetic factors. Early work using hybrids between Drosophila koepferae (Dk) and Drosophila buzzatii (Db) was consistent with the idea that HMS requires the cooperation of several genetic factors, supporting a polygenic threshold (PT) model. Here we present a genome-wide mapping strategy to test the PT model, analyzing serially backcrossed fertile and sterile males in which the Dk genome was introgressed into the Db background. We identified 32 Dk-specific markers significantly associated with hybrid sterility. Our results demonstrate 1) a strong correlation between the number of segregated sterility markers and males' degree of sterility, 2) the exchangeability among markers, 3) their tendency to cluster into low-recombining chromosomal regions, and 4) the requirement for a minimum number (threshold) of markers to elicit sterility. Although our findings do not contradict a role for occasional major hybrid-sterility genes, they conform more to the view that HMS primarily evolves by the cumulative action of many interacting genes of minor effect in a complex PT architecture.

  11. Functionalized hybrid nanofibers to mimic native ECM for tissue engineering applications

    International Nuclear Information System (INIS)

    Karuppuswamy, Priyadharsini; Venugopal, Jayarama Reddy; Navaneethan, Balchandar; Laiva, Ashang Luwang; Sridhar, Sreepathy; Ramakrishna, Seeram

    2014-01-01

    Highlights: • Functionalized hybrid polymer mats fabricated for tissue engineering. • Hybrid polymer mats showed high surface area, high porosity and good wettability. • Incorporation of natural polymers modified the properties of nanofiber mats more biologically favorable for biomedical applications. - Abstract: Nanotechnology being one of the most promising technologies today shows an extremely huge potential in the field of tissue engineering to mimic the porous topography of natural extracellular matrix (ECM). Natural polymers are incorporated into the synthetic polymers to fabricate functionalized hybrid nanofibrous scaffolds, which improve cell and tissue compatibility. The present study identified the biopolymers – aloe vera, silk fibroin and curcumin incorporated into polycaprolactone (PCL) as suitable substrates for tissue engineering. Different combinations of PCL with natural polymers – PCL/aloe vera, PCL/silk fibroin, PCL/aloe vera/silk fibroin, PCL/aloe vera/silk fibroin/curcumin were electrospun into nanofibrous scaffolds. The fabricated two dimensional nanofibrous scaffolds showed high surface area, appropriate mechanical properties, hydrophilicity and porosity, required for the regeneration of diseased tissues. The nanofibrous scaffolds were characterized by Scanning electron microscope (SEM), porometry, Instron tensile tester, VCA optima contact angle measurement and FTIR to analyze the fiber diameter and morphology, porosity and pore size distribution, mechanical strength, wettability, chemical bonds and functional groups, respectively. The average fiber diameter of obtained fibers ranged from 250 nm to 350 nm and the tensile strength of PCL scaffolds at 4.49 MPa increased upto 8.3 MPa for PCL/silk fibroin scaffolds. Hydrophobicity of PCL decreased with the incorporation of natural polymers, especially for PCL/aloe vera scaffolds. The properties of as-spun nanofiber scaffolds showed their potential as promising scaffold materials in

  12. Functionalized hybrid nanofibers to mimic native ECM for tissue engineering applications

    Energy Technology Data Exchange (ETDEWEB)

    Karuppuswamy, Priyadharsini [Center for Nanofibers and Nanotechnology, Nanoscience and Nanotechnology Initiative, Faculty of Engineering, National University of Singapore, Singapore (Singapore); Department Physics and Nanotechnology, SRM University, Kattankulathur, Chennai (India); Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Venugopal, Jayarama Reddy, E-mail: nnijrv@nus.edu.sg [Center for Nanofibers and Nanotechnology, Nanoscience and Nanotechnology Initiative, Faculty of Engineering, National University of Singapore, Singapore (Singapore); Navaneethan, Balchandar [Center for Nanofibers and Nanotechnology, Nanoscience and Nanotechnology Initiative, Faculty of Engineering, National University of Singapore, Singapore (Singapore); Department Physics and Nanotechnology, SRM University, Kattankulathur, Chennai (India); Laiva, Ashang Luwang; Sridhar, Sreepathy; Ramakrishna, Seeram [Center for Nanofibers and Nanotechnology, Nanoscience and Nanotechnology Initiative, Faculty of Engineering, National University of Singapore, Singapore (Singapore)

    2014-12-15

    Highlights: • Functionalized hybrid polymer mats fabricated for tissue engineering. • Hybrid polymer mats showed high surface area, high porosity and good wettability. • Incorporation of natural polymers modified the properties of nanofiber mats more biologically favorable for biomedical applications. - Abstract: Nanotechnology being one of the most promising technologies today shows an extremely huge potential in the field of tissue engineering to mimic the porous topography of natural extracellular matrix (ECM). Natural polymers are incorporated into the synthetic polymers to fabricate functionalized hybrid nanofibrous scaffolds, which improve cell and tissue compatibility. The present study identified the biopolymers – aloe vera, silk fibroin and curcumin incorporated into polycaprolactone (PCL) as suitable substrates for tissue engineering. Different combinations of PCL with natural polymers – PCL/aloe vera, PCL/silk fibroin, PCL/aloe vera/silk fibroin, PCL/aloe vera/silk fibroin/curcumin were electrospun into nanofibrous scaffolds. The fabricated two dimensional nanofibrous scaffolds showed high surface area, appropriate mechanical properties, hydrophilicity and porosity, required for the regeneration of diseased tissues. The nanofibrous scaffolds were characterized by Scanning electron microscope (SEM), porometry, Instron tensile tester, VCA optima contact angle measurement and FTIR to analyze the fiber diameter and morphology, porosity and pore size distribution, mechanical strength, wettability, chemical bonds and functional groups, respectively. The average fiber diameter of obtained fibers ranged from 250 nm to 350 nm and the tensile strength of PCL scaffolds at 4.49 MPa increased upto 8.3 MPa for PCL/silk fibroin scaffolds. Hydrophobicity of PCL decreased with the incorporation of natural polymers, especially for PCL/aloe vera scaffolds. The properties of as-spun nanofiber scaffolds showed their potential as promising scaffold materials in

  13. A study of correlation functions for the delta-function fermi gas

    International Nuclear Information System (INIS)

    Berkovich, A.

    1987-01-01

    In this dissertation, the author considers the quantum nonlinear Schrodinger model, describing a non-relativistic, finite-density gas of one-dimensional fermions with repulsive delta-function interaction. The author employs the quantum inverse scattering method and temperature Green function technique to derive some new results for the two-point, equal-time correlation function. For the case of zero temperature, it is shown that the correlation function in the infinite coupling limit (c → ∞) can be expressed concisely in terms of the solution of the Painleve equation of the fifth kind. The author, then, extends this result and obtains an exact expression for the order (1/c) correction to the two-point function in terms of the Painleve transcendents. This work is essentially self-contained; both old and new results are presented and discussed at some length

  14. The correlation function for density perturbations in an expanding universe. III The three-point and predictions of the four-point and higher order correlation functions

    Science.gov (United States)

    Mcclelland, J.; Silk, J.

    1978-01-01

    Higher-order correlation functions for the large-scale distribution of galaxies in space are investigated. It is demonstrated that the three-point correlation function observed by Peebles and Groth (1975) is not consistent with a distribution of perturbations that at present are randomly distributed in space. The two-point correlation function is shown to be independent of how the perturbations are distributed spatially, and a model of clustered perturbations is developed which incorporates a nonuniform perturbation distribution and which explains the three-point correlation function. A model with hierarchical perturbations incorporating the same nonuniform distribution is also constructed; it is found that this model also explains the three-point correlation function, but predicts different results for the four-point and higher-order correlation functions than does the model with clustered perturbations. It is suggested that the model of hierarchical perturbations might be explained by the single assumption of having density fluctuations or discrete objects all of the same mass randomly placed at some initial epoch.

  15. Measurement of spatial correlation functions using image processing techniques

    International Nuclear Information System (INIS)

    Berryman, J.G.

    1985-01-01

    A procedure for using digital image processing techniques to measure the spatial correlation functions of composite heterogeneous materials is presented. Methods for eliminating undesirable biases and warping in digitized photographs are discussed. Fourier transform methods and array processor techniques for calculating the spatial correlation functions are treated. By introducing a minimal set of lattice-commensurate triangles, a method of sorting and storing the values of three-point correlation functions in a compact one-dimensional array is developed. Examples are presented at each stage of the analysis using synthetic photographs of cross sections of a model random material (the penetrable sphere model) for which the analytical form of the spatial correlations functions is known. Although results depend somewhat on magnification and on relative volume fraction, it is found that photographs digitized with 512 x 512 pixels generally have sufficiently good statistics for most practical purposes. To illustrate the use of the correlation functions, bounds on conductivity for the penetrable sphere model are calculated with a general numerical scheme developed for treating the singular three-dimensional integrals which must be evaluated

  16. First-order-reversal-curve analysis of exchange-coupled SmCo/NdFeB nanocomposite alloys

    International Nuclear Information System (INIS)

    Pan, Mingxiang; Zhang, Pengyue; Ge, Hongliang; Yu, Nengjun; Wu, Qiong

    2014-01-01

    Exchange-coupled SmCo 5 /Nd 2 Fe 14 B nanocomposite magnets have been fabricated by ball milling of the micrometer sized SmCo 5 and Nd 2 Fe 14 B powders. The influence of Nd 2 Fe 14 B content on the microstructure and magnetic properties of these hybrid alloys was investigated. The alloys that show strong intergrain exchange-coupling behavior with (BH) max =2.95 MGOe was obtained when the two hard phases are well coupled. A first-order-reversal-curve (FORC) analysis was performed for both SmCo 5 single-phase magnet and SmCo 5 /Nd 2 Fe 14 B hybrid magnet; the FORC diagrams results show two major peaks for the hybrid magnets. In both cases, the magnetization reversal behaviors for these alloys were discussed in detail and are consistent with the results of δM plots. - Highlights: • Exchange-coupled SmCo 5 /Nd 2 Fe 14 B nanocomposite magnets were studied. • Magnetization reversal behaviors of the hybrid magnet were discussed. • The FORCs analysis is taken to identify the optimal conditions for hybrid magnet

  17. Immobilization of carbon nanotubes on functionalized graphene film grown by chemical vapor deposition and characterization of the hybrid material

    Directory of Open Access Journals (Sweden)

    Prashanta Dhoj Adhikari

    2014-01-01

    Full Text Available We report the surface functionalization of graphene films grown by chemical vapor deposition and fabrication of a hybrid material combining multi-walled carbon nanotubes and graphene (CNT–G. Amine-terminated self-assembled monolayers were prepared on graphene by the UV-modification of oxidized groups introduced onto the film surface. Amine-termination led to effective interaction with functionalized CNTs to assemble a CNT–G hybrid through covalent bonding. Characterization clearly showed no defects of the graphene film after the immobilization reaction with CNT. In addition, the hybrid graphene material revealed a distinctive CNT–G structure and p–n type electrical properties. The introduction of functional groups on the graphene film surface and fabrication of CNT–G hybrids with the present technique could provide an efficient, novel route to device fabrication.

  18. Hybrid Theory of P-Wave Electron-Hydrogen Elastic Scattering

    Science.gov (United States)

    Bhatia, Anand

    2012-01-01

    We report on a study of electron-hydrogen scattering, using a combination of a modified method of polarized orbitals and the optical potential formalism. The calculation is restricted to P waves in the elastic region, where the correlation functions are of Hylleraas type. It is found that the phase shifts are not significantly affected by the modification of the target function by a method similar to the method of polarized orbitals and they are close to the phase shifts calculated earlier by Bhatia. This indicates that the correlation function is general enough to include the target distortion (polarization) in the presence of the incident electron. The important fact is that in the present calculation, to obtain similar results only 35-term correlation function is needed in the wave function compared to the 220-term wave function required in the above-mentioned previous calculation. Results for the phase shifts, obtained in the present hybrid formalism, are rigorous lower bounds to the exact phase shifts.

  19. Direct Determination of Absolute Configuration of Methyl-Substituted Phenyloxiranes: A Combined Experimental and Theoretical Approach

    DEFF Research Database (Denmark)

    Fristrup, Peter; Lassen, Peter Rygaard; Johannessen, Christian

    2006-01-01

    obtained from quantum mechanical calculations (density functional theory with the B3LYP hybrid exchange correlation functional with 6-31++G**, aug-cc-pVDZ, or aug-cc-pVTZ basis set) and related to the physical structure of the compounds. The absolute configuration could be established directly in each case...

  20. A partitioned correlation function interaction approach for describing electron correlation in atoms

    International Nuclear Information System (INIS)

    Verdebout, S; Godefroid, M; Rynkun, P; Jönsson, P; Gaigalas, G; Fischer, C Froese

    2013-01-01

    The traditional multiconfiguration Hartree–Fock (MCHF) and configuration interaction (CI) methods are based on a single orthonormal orbital basis. For atoms with many closed core shells, or complicated shell structures, a large orbital basis is needed to saturate the different electron correlation effects such as valence, core–valence and correlation within the core shells. The large orbital basis leads to massive configuration state function (CSF) expansions that are difficult to handle, even on large computer systems. We show that it is possible to relax the orthonormality restriction on the orbital basis and break down the originally very large calculations into a series of smaller calculations that can be run in parallel. Each calculation determines a partitioned correlation function (PCF) that accounts for a specific correlation effect. The PCFs are built on optimally localized orbital sets and are added to a zero-order multireference (MR) function to form a total wave function. The expansion coefficients of the PCFs are determined from a low dimensional generalized eigenvalue problem. The interaction and overlap matrices are computed using a biorthonormal transformation technique (Verdebout et al 2010 J. Phys. B: At. Mol. Phys. 43 074017). The new method, called partitioned correlation function interaction (PCFI), converges rapidly with respect to the orbital basis and gives total energies that are lower than the ones from ordinary MCHF and CI calculations. The PCFI method is also very flexible when it comes to targeting different electron correlation effects. Focusing our attention on neutral lithium, we show that by dedicating a PCF to the single excitations from the core, spin- and orbital-polarization effects can be captured very efficiently, leading to highly improved convergence patterns for hyperfine parameters compared with MCHF calculations based on a single orthogonal radial orbital basis. By collecting separately optimized PCFs to correct the

  1. A partitioned correlation function interaction approach for describing electron correlation in atoms

    Science.gov (United States)

    Verdebout, S.; Rynkun, P.; Jönsson, P.; Gaigalas, G.; Froese Fischer, C.; Godefroid, M.

    2013-04-01

    The traditional multiconfiguration Hartree-Fock (MCHF) and configuration interaction (CI) methods are based on a single orthonormal orbital basis. For atoms with many closed core shells, or complicated shell structures, a large orbital basis is needed to saturate the different electron correlation effects such as valence, core-valence and correlation within the core shells. The large orbital basis leads to massive configuration state function (CSF) expansions that are difficult to handle, even on large computer systems. We show that it is possible to relax the orthonormality restriction on the orbital basis and break down the originally very large calculations into a series of smaller calculations that can be run in parallel. Each calculation determines a partitioned correlation function (PCF) that accounts for a specific correlation effect. The PCFs are built on optimally localized orbital sets and are added to a zero-order multireference (MR) function to form a total wave function. The expansion coefficients of the PCFs are determined from a low dimensional generalized eigenvalue problem. The interaction and overlap matrices are computed using a biorthonormal transformation technique (Verdebout et al 2010 J. Phys. B: At. Mol. Phys. 43 074017). The new method, called partitioned correlation function interaction (PCFI), converges rapidly with respect to the orbital basis and gives total energies that are lower than the ones from ordinary MCHF and CI calculations. The PCFI method is also very flexible when it comes to targeting different electron correlation effects. Focusing our attention on neutral lithium, we show that by dedicating a PCF to the single excitations from the core, spin- and orbital-polarization effects can be captured very efficiently, leading to highly improved convergence patterns for hyperfine parameters compared with MCHF calculations based on a single orthogonal radial orbital basis. By collecting separately optimized PCFs to correct the MR

  2. Moment generating function approach to pricing interest rate and foreign exchange rate claims

    NARCIS (Netherlands)

    Dijkstra, T.K.; Yao, Y.

    2002-01-01

    This paper uses moment generating functions to provide a general framework to model international term structures and to price interest rate and foreign exchange rate claims. When moment generating functions of state variables have a closed-form formula, closed-form formulas for bond prices are

  3. First principle approach to correlation functions of spin-1/2 Heisenberg chain: fourth-neighbor correlators

    International Nuclear Information System (INIS)

    Boos, H.E.; Shiroishi, M.; Takahashi, M.

    2005-01-01

    We show how correlation functions of the spin-1/2 Heisenberg chain without magnetic field in the anti-ferromagnetic ground state can be explicitly calculated using information contained in the quantum Knizhnik-Zamolodchikov equation [qKZ]. We find several fundamental relations which the inhomogeneous correlations should fulfill. On the other hand, it turns out that these relations can fix the form of the correlations uniquely. Actually, applying this idea, we have obtained all the correlation functions on five sites. Particularly by taking the homogeneous limit, we have got the analytic form of the fourth-neighbor pair correlator j z S j+4 z >

  4. Hybrid image and blood sampling input function for quantification of small animal dynamic PET data

    International Nuclear Information System (INIS)

    Shoghi, Kooresh I.; Welch, Michael J.

    2007-01-01

    We describe and validate a hybrid image and blood sampling (HIBS) method to derive the input function for quantification of microPET mice data. The HIBS algorithm derives the peak of the input function from the image, which is corrected for recovery, while the tail is derived from 5 to 6 optimally placed blood sampling points. A Bezier interpolation algorithm is used to link the rightmost image peak data point to the leftmost blood sampling point. To assess the performance of HIBS, 4 mice underwent 60-min microPET imaging sessions following a 0.40-0.50-mCi bolus administration of 18 FDG. In total, 21 blood samples (blood-sampled plasma time-activity curve, bsPTAC) were obtained throughout the imaging session to compare against the proposed HIBS method. MicroPET images were reconstructed using filtered back projection with a zoom of 2.75 on the heart. Volumetric regions of interest (ROIs) were composed by drawing circular ROIs 3 pixels in diameter on 3-4 transverse planes of the left ventricle. Performance was characterized by kinetic simulations in terms of bias in parameter estimates when bsPTAC and HIBS are used as input functions. The peak of the bsPTAC curve was distorted in comparison to the HIBS-derived curve due to temporal limitations and delay in blood sampling, which affected the rates of bidirectional exchange between plasma and tissue. The results highlight limitations in using bsPTAC. The HIBS method, however, yields consistent results, and thus, is a substitute for bsPTAC

  5. Green function theory of random ferromagnets with large exchange anisotropy

    International Nuclear Information System (INIS)

    Patterson, J.D.

    1977-01-01

    Spin 1/2 systems which are coupled with an Ising-like Hamiltonian with fluctuating exchange are discussed by the use of thermodynamic Green functions in four different approximations. The first is equivalent to a local mean field approximation and the second is an approximation to the first in which the local mean field is assumed to be proportional to the overall magnetization and to the sum of the neighboring exchange 'bonds'. The third is also a special case of the first, but the local mean field is approximated in such a way as to be appropriate for the discussion of spin glasses. The fourth is a coherent potential-like approximation (CPA). The second approximation can be shown to imply no reduction of the Curie temperature (T sub(c)) due to exchange fluctuations, while the CPA does result in a lowering of T sub(c) (assuming small fluctuations about an average positive exchange in both cases). However, the CPA that was used is also an approximation to the second method. Hence, even though the CPA does result in a lowering of T sub(c) (which is generally conceded to be correct for the original model), this fact cannot be used as an argument for the validity of the CPA. This calculation thus emphasizes the necessity of critically examining any CPA-like calculation before accepting its predictions as valid [pt

  6. Anticorrosive organic/inorganic hybrid coatings

    Science.gov (United States)

    Gao, Tongzhai

    Organic/inorganic hybrid coating system was developed for anticorrosion applications using polyurea, polyurethane or epoxide as the organic phase and polysiloxane, formed by sol-gel process, as the inorganic phase. Polyurea/polysiloxane hybrid coatings were formulated and moisture cured using HDI isocyanurate, alkoxysilane-functionalized HDI isocyanurate, and tetraethyl orthosilicate (TEOS) oligomers. Two urethanes were prepared using the same components as abovementioned in addition to the oligoesters derived from either cyclohexane diacids (CHDA) and 2-butyl-2-ethyl-1,3-propanediol (BEPD) or adipic acid (AA), isophthalic acid (IPA), 1,6-hexanediol (HD), and trimethylol propane (TMP). Accelerated weathering and outdoor exposure were performed to study the weatherability of the polyurethane/polysiloxane hybrid coating system. FTIR and solid-state 13C NMR revealed that the degradation of the hybrid coatings occurred at the urethane and ester functionalities of the organic phase. DMA and DSC analyses showed the glass transition temperature increased and broadened after weathering. SEM was employed to observe the change of morphology of the hybrid coatings and correlated with the gloss variation after weathering. Rutile TiO2 was formulated into polyurethane/polysiloxane hybrid coatings in order to investigate the effect of pigmentation on the coating properties and the sol-gel precursor. Chemical interaction between the TiO2 and the sol-gel precursor was investigated using solid-state 29Si NMR and XPS. The morphology, mechanical, viscoelastic, thermal properties of the pigmented coatings were evaluated as a function of pigmentation volume concentration (PVC). Using AFM and SEM, the pigment were observed to be well dispersed in the polymer matrix. The thermal stability, the tensile modulus and strength of the coatings were enhanced with increasing PVC, whereas the pull-off adhesion and flexibility were reduced with increasing PVC. Finally, the pigmented coatings were

  7. Hybrid MR-PET of brain tumours using amino acid PET and chemical exchange saturation transfer MRI.

    Science.gov (United States)

    da Silva, N A; Lohmann, P; Fairney, J; Magill, A W; Oros Peusquens, A-M; Choi, C-H; Stirnberg, R; Stoffels, G; Galldiks, N; Golay, X; Langen, K-J; Jon Shah, N

    2018-06-01

    PET using radiolabelled amino acids has become a promising tool in the diagnostics of gliomas and brain metastasis. Current research is focused on the evaluation of amide proton transfer (APT) chemical exchange saturation transfer (CEST) MR imaging for brain tumour imaging. In this hybrid MR-PET study, brain tumours were compared using 3D data derived from APT-CEST MRI and amino acid PET using O-(2- 18 F-fluoroethyl)-L-tyrosine ( 18 F-FET). Eight patients with gliomas were investigated simultaneously with 18 F-FET PET and APT-CEST MRI using a 3-T MR-BrainPET scanner. CEST imaging was based on a steady-state approach using a B 1 average power of 1μT. B 0 field inhomogeneities were corrected a Prametric images of magnetisation transfer ratio asymmetry (MTR asym ) and differences to the extrapolated semi-solid magnetisation transfer reference method, APT# and nuclear Overhauser effect (NOE#), were calculated. Statistical analysis of the tumour-to-brain ratio of the CEST data was performed against PET data using the non-parametric Wilcoxon test. A tumour-to-brain ratio derived from APT# and 18 F-FET presented no significant differences, and no correlation was found between APT# and 18 F-FET PET data. The distance between local hot spot APT# and 18 F-FET were different (average 20 ± 13 mm, range 4-45 mm). For the first time, CEST images were compared with 18 F-FET in a simultaneous MR-PET measurement. Imaging findings derived from 18 F-FET PET and APT CEST MRI seem to provide different biological information. The validation of these imaging findings by histological confirmation is necessary, ideally using stereotactic biopsy.

  8. Hybride textuelle Strukturen und hybride textuelle Einheiten. Ein Beitrag zur Theorie der Wörterbuchform

    Directory of Open Access Journals (Sweden)

    Herbert Ernst Wiegand

    2011-10-01

    Textsegmentklassen aufweisen (vgl. die Stichwörter.

    Stichwörter: ANGABERELATION, ELEMENTENHETEROGENE TRÄGERMENGE, FUNKTIONALER ANGABEZUSATZ, FUNKTIONAL-POSITIONALE SEGMENTATION, HIERARCHISCHE ARCHITEKTONISCH ANGEREICHERTE ARTIKELMIKROSTRUKTUR, HIERARCHISCHE HYBRIDE ANGABENKONSTITUENTENSTRUKTUR MIT GLOSSATBEDINGTER TEILSTRUKTUR, HIERARCHISCHE HYBRIDE ANGABENSTRUKTUR, HIERARCHISCHE HYBRIDE ARTIKELKONSTITUENTENSTRUKTUR, HIERARCHISCHE HYBRIDE ARTIKELMIKROSTRUKTUR, HIERARCHISCHE HYBRIDE EXHAUSTIVE ANGABENSTRUKTUR, HIERARCHISCHE HYBRIDE GLOSSATBEDINGTE ANGABESTRUKTUR, HIERARCHISCHE HYBRIDE FLACHE DOPPELGLOSSATBEDINGTE ANGABESTRUKTUR, HIERARCHISCHE HYBRIDE MINIMIERTE GLOSSATBEDINGTE ANGABESTRUKTUR, HIERARCHISCHE HYBRIDE TEXTKONSTITUENTENSTRUKTUR, HIERARCHISCHE HYBRIDE TIEFE DOPPELGLOSSATBEDINGTE ANGABESTRUKTUR, HIERARCHISCHE REINE TEXTKONSTITUENTENSTRUKTUR, HYBRIDE VERWEISKENNZEICHNUNG, NICHTFUNKTIONALE-POSITIONALE SEGMENTATION, ORDNUNGSRELATION, SEGMENTATIVE ISOLIERUNG, VERTIKALE ANGABEARCHITEKTUR

     

    ABSTRACT: Hybrid textual structures and hybrid textual units. A contribution to the theory of dictionary structures. In this contribution, the formation, presentation and performance of hybrid textual structures that display accessible entries are discussed by using examples from dictionary articles. The features of hybrid textual units are also explained. A dictionary article in a printed dictionary always displays both a hierarchical pure and a hierarchical hybrid text constituent structure, when it contains at least one functional item addition, e.g. an upward- or downward- or an internally-expanded one. Because functional item additions are text segments with an item function but without text constituent status, they are enabled by means of non-functional segmentation, so that both functional and non-functional text segments prevail. During the formation of structures they then enter the structure-carrying set so that the structurecarrying set of all hybrid

  9. Lifetime information from correlation functions selected by directional cuts

    International Nuclear Information System (INIS)

    Gelbke, C.K.

    1995-01-01

    Two-particle correlation functions provide information on the space-time characteristics of the emitting source. In many cases, ambiguities of the relative magnitudes of source radius and lifetime can be reduced by analysis of correlation functions evaluated for specific directional cuts on the relative velocity of the coincident particle pair. Information on non-spherical breakup geometries is more difficult to extract. Examples of two-proton correlation functions in which directional cuts are employed to reduce existing space-time ambiguities for the emitting system are presented. (author). 50 refs., 10 figs

  10. Numerical investigation of transient behaviour of the recuperative heat exchanger in a MR J-T cryocooler using different heat transfer correlations

    Science.gov (United States)

    Damle, R. M.; Ardhapurkar, P. M.; Atrey, M. D.

    2016-12-01

    In J-T cryocoolers operating with mixed refrigerants (nitrogen-hydrocarbons), the recuperative heat exchange takes place under two-phase conditions. Simultaneous boiling of the low pressure stream and condensation of the high pressure stream results in higher heat transfer coefficients. The mixture composition, operating conditions and the heat exchanger design are crucial for obtaining the required cryogenic temperature. In this work, a one-dimensional transient algorithm is developed for the simulation of the two-phase heat transfer in the recuperative heat exchanger of a mixed refrigerant J-T cryocooler. Modified correlation is used for flow boiling of the high pressure fluid while different condensation correlations are employed with and without the correction for the low pressure fluid. Simulations are carried out for different mixture compositions and numerical predictions are compared with the experimental data. The overall heat transfer is predicted reasonably well and the qualitative trends of the temperature profiles are also captured by the developed numerical model.

  11. Partitioning inter annual variability in net ecosystem exchange between climatic variability and functional change

    International Nuclear Information System (INIS)

    Hui, D.; Luo, Y.; Katul, G.

    2003-01-01

    Inter annual variability in net ecosystem exchange of carbon is investigated using a homogeneity-of-slopes model to identify the function change contributing to inter annual variability, net ecosystem carbon exchange, and night-time ecosystem respiration. Results of employing this statistical approach to a data set collected at the Duke Forest AmeriFlux site from August 1997 to December 2001 are discussed. The results demonstrate that it is feasible to partition the variation in ecosystem carbon fluxes into direct effects of seasonal and inter annual climatic variability and functional change. 51 refs., 4 tabs., 5 figs

  12. G-centers in irradiated silicon revisited: A screened hybrid density functional theory approach

    KAUST Repository

    Wang, H.; Chroneos, A.; Londos, C. A.; Sgourou, E. N.; Schwingenschlö gl, Udo

    2014-01-01

    Electronic structure calculations employing screened hybrid density functional theory are used to gain fundamental insight into the interaction of carbon interstitial (Ci) and substitutional (Cs) atoms forming the CiCs defect known as G

  13. A test of conformal invariance: Correlation functions on a disk

    International Nuclear Information System (INIS)

    Badke, R.; Rittenberg, V.; Ruegg, H.

    1985-06-01

    Using conformal invariance one can derive the correlation functions of a disk from those in the half-plane. The correlation function in the half-plane is determined by the 'small' conformal invariance up to an unknown function of one variable. By measuring through the Monte Carlo method the correlation function for two different configurations, the unknown function can be eliminated and one obtains a test of conformal invariance. It is shown that the Ising and the three state Potts model pass the test for very small lattices. (orig.)

  14. Open Field Study of Some Zea mays Hybrids, Lipid Compounds and Fumonisins Accumulation

    Science.gov (United States)

    Giorni, Paola; Dall’Asta, Chiara; Reverberi, Massimo; Scala, Valeria; Ludovici, Matteo; Cirlini, Martina; Galaverna, Gianni; Fanelli, Corrado; Battilani, Paola

    2015-01-01

    Lipid molecules are increasingly recognized as signals exchanged by organisms interacting in pathogenic and/or symbiotic ways. Some classes of lipids actively determine the fate of the interactions. Host cuticle/cell wall/membrane components such as sphingolipids and oxylipins may contribute to determining the fate of host–pathogen interactions. In the present field study, we considered the relationship between specific sphingolipids and oxylipins of different hybrids of Zea mays and fumonisin by F. verticillioides, sampling ears at different growth stages from early dough to fully ripe. The amount of total and free fumonisin differed significantly between hybrids and increased significantly with maize ripening. Oxylipins and phytoceramides changed significantly within the hybrids and decreased with kernel maturation, starting from physiological maturity. Although the correlation between fumonisin accumulation and plant lipid profile is certain, the data collected so far cannot define a cause-effect relationship but open up new perspectives. Therefore, the question—“Does fumonisin alter plant lipidome or does plant lipidome modulate fumonisin accumulation?”—is still open. PMID:26378580

  15. Open Field Study of Some Zea mays Hybrids, Lipid Compounds and Fumonisins Accumulation

    Directory of Open Access Journals (Sweden)

    Paola Giorni

    2015-09-01

    Full Text Available Lipid molecules are increasingly recognized as signals exchanged by organisms interacting in pathogenic and/or symbiotic ways. Some classes of lipids actively determine the fate of the interactions. Host cuticle/cell wall/membrane components such as sphingolipids and oxylipins may contribute to determining the fate of host–pathogen interactions. In the present field study, we considered the relationship between specific sphingolipids and oxylipins of different hybrids of Zea mays and fumonisin by F. verticillioides, sampling ears at different growth stages from early dough to fully ripe. The amount of total and free fumonisin differed significantly between hybrids and increased significantly with maize ripening. Oxylipins and phytoceramides changed significantly within the hybrids and decreased with kernel maturation, starting from physiological maturity. Although the correlation between fumonisin accumulation and plant lipid profile is certain, the data collected so far cannot define a cause-effect relationship but open up new perspectives. Therefore, the question—“Does fumonisin alter plant lipidome or does plant lipidome modulate fumonisin accumulation?”—is still open.

  16. Difficulties in applying pure Kohn-Sham density functional theory electronic structure methods to protein molecules

    Science.gov (United States)

    Rudberg, Elias

    2012-02-01

    Self-consistency-based Kohn-Sham density functional theory (KS-DFT) electronic structure calculations with Gaussian basis sets are reported for a set of 17 protein-like molecules with geometries obtained from the Protein Data Bank. It is found that in many cases such calculations do not converge due to vanishing HOMO-LUMO gaps. A sequence of polyproline I helix molecules is also studied and it is found that self-consistency calculations using pure functionals fail to converge for helices longer than six proline units. Since the computed gap is strongly correlated to the fraction of Hartree-Fock exchange, test calculations using both pure and hybrid density functionals are reported. The tested methods include the pure functionals BLYP, PBE and LDA, as well as Hartree-Fock and the hybrid functionals BHandHLYP, B3LYP and PBE0. The effect of including solvent molecules in the calculations is studied, and it is found that the inclusion of explicit solvent molecules around the protein fragment in many cases gives a larger gap, but that convergence problems due to vanishing gaps still occur in calculations with pure functionals. In order to achieve converged results, some modeling of the charge distribution of solvent water molecules outside the electronic structure calculation is needed. Representing solvent water molecules by a simple point charge distribution is found to give non-vanishing HOMO-LUMO gaps for the tested protein-like systems also for pure functionals.

  17. Difficulties in applying pure Kohn-Sham density functional theory electronic structure methods to protein molecules

    International Nuclear Information System (INIS)

    Rudberg, Elias

    2012-01-01

    Self-consistency-based Kohn-Sham density functional theory (KS-DFT) electronic structure calculations with Gaussian basis sets are reported for a set of 17 protein-like molecules with geometries obtained from the Protein Data Bank. It is found that in many cases such calculations do not converge due to vanishing HOMO-LUMO gaps. A sequence of polyproline I helix molecules is also studied and it is found that self-consistency calculations using pure functionals fail to converge for helices longer than six proline units. Since the computed gap is strongly correlated to the fraction of Hartree-Fock exchange, test calculations using both pure and hybrid density functionals are reported. The tested methods include the pure functionals BLYP, PBE and LDA, as well as Hartree-Fock and the hybrid functionals BHandHLYP, B3LYP and PBE0. The effect of including solvent molecules in the calculations is studied, and it is found that the inclusion of explicit solvent molecules around the protein fragment in many cases gives a larger gap, but that convergence problems due to vanishing gaps still occur in calculations with pure functionals. In order to achieve converged results, some modeling of the charge distribution of solvent water molecules outside the electronic structure calculation is needed. Representing solvent water molecules by a simple point charge distribution is found to give non-vanishing HOMO-LUMO gaps for the tested protein-like systems also for pure functionals. (fast track communication)

  18. The electricity exchange. On the organisation and latent functions of electricity exchange trading as seen from the viewpoint of market sociology; Die Stromboerse. Ueber Form und latente Funktionen des boerslichen Stromhandels aus marktsoziologischer Sicht

    Energy Technology Data Exchange (ETDEWEB)

    Giacovelli, Sebastian

    2014-07-01

    Electricity exchange trading in Germany has existed since the year 2000. Since this time, the Leipzig electricity exchange, a reference market for off-exchange electricity trading, has operated in an environment marked by both criticism and acceptance. Taking this field of controversy as a point of departure the present empirical study in market sociology undertakes to investigate the organisation and latent functions of electricity exchange trading. The ensuing analysis provides answers to questions as to how prices are formed on the electricity exchange and what officially incommunicable functions are served by price formation on exchanges.

  19. A role of nanotube dangling pyrrole and oxygen functions in the electrochemical synthesis of polypyrrole/MWCNTs hybrid materials

    International Nuclear Information System (INIS)

    Krukiewicz, Katarzyna; Herman, Artur P.; Turczyn, Roman; Szymańska, Katarzyna; Koziol, Krzysztof K.K.; Boncel, Sławomir; Zak, Jerzy K.

    2014-01-01

    Highlights: • The effect of MWCNT functionalization on properties of PPy composites was explained. • The behavior of pristine, pyrrole-modified and oxidized MWCNT was explained. • Functionalization of MWCNT improved their dispersibility and processability. • Different mechanisms of (f-)MWCNT incorporation into PPy composites were explained. • Orientation of growing PPy chains was tailored through the addition of (f-)MWCNT. - Abstract: The effect of the functionalization of multi-walled carbon nanotubes (MWCNTs) on the process of electrochemical co-deposition of MWCNTs and polypyrrole (PPy), as well as the morphology of obtained composites have been demonstrated. As the nanotube components of the hybrids, three types of MWCNT were used, namely c-CVD derived (pristine) MWCNTs, their oxidized counterparts MWCNT-Ox and pyrrole-modified MWCNT-Py. The stability of pristine and functionalized MWCNTs (f-MWCNT) dispersions in tetrahydrofuran and water was studied together with the description of the process of formation PPy/(f-)MWCNT hybrid materials via electrochemical co-deposition. The structural and morphological properties of the hybrids were characterized by Raman spectroscopy, scanning electron microscopy and atomic force microscopy revealing substantial differences among hybrid materials in their surface morphology and the influence of MWCNT functionalization on the orientation of growing PPy chains

  20. A role of nanotube dangling pyrrole and oxygen functions in the electrochemical synthesis of polypyrrole/MWCNTs hybrid materials

    Energy Technology Data Exchange (ETDEWEB)

    Krukiewicz, Katarzyna, E-mail: katarzyna.krukiewicz@polsl.pl [Department of Physical Chemistry and Technology of Polymers, Silesian University of Technology, Strzody 9, 44-100 Gliwice (Poland); Herman, Artur P., E-mail: artur.herman@polsl.pl [Department of Organic Chemistry, Bioorganic Chemistry and Biotechnology, Silesian University of Technology, Krzywoustego 4, Gliwice 44-100 (Poland); Turczyn, Roman, E-mail: roman.turczyn@polsl.pl [Department of Physical Chemistry and Technology of Polymers, Silesian University of Technology, Strzody 9, 44-100 Gliwice (Poland); Szymańska, Katarzyna, E-mail: katarzyna.szymanska@polsl.pl [Department of Chemical and Process Engineering, Silesian University of Technology, Strzody 7, 44-100 Gliwice (Poland); Koziol, Krzysztof K.K., E-mail: kk292@cam.ac.uk [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Boncel, Sławomir, E-mail: slawomir.boncel@polsl.pl [Department of Organic Chemistry, Bioorganic Chemistry and Biotechnology, Silesian University of Technology, Krzywoustego 4, Gliwice 44-100 (Poland); Zak, Jerzy K., E-mail: jerzy.zak@polsl.pl [Department of Physical Chemistry and Technology of Polymers, Silesian University of Technology, Strzody 9, 44-100 Gliwice (Poland)

    2014-10-30

    Highlights: • The effect of MWCNT functionalization on properties of PPy composites was explained. • The behavior of pristine, pyrrole-modified and oxidized MWCNT was explained. • Functionalization of MWCNT improved their dispersibility and processability. • Different mechanisms of (f-)MWCNT incorporation into PPy composites were explained. • Orientation of growing PPy chains was tailored through the addition of (f-)MWCNT. - Abstract: The effect of the functionalization of multi-walled carbon nanotubes (MWCNTs) on the process of electrochemical co-deposition of MWCNTs and polypyrrole (PPy), as well as the morphology of obtained composites have been demonstrated. As the nanotube components of the hybrids, three types of MWCNT were used, namely c-CVD derived (pristine) MWCNTs, their oxidized counterparts MWCNT-Ox and pyrrole-modified MWCNT-Py. The stability of pristine and functionalized MWCNTs (f-MWCNT) dispersions in tetrahydrofuran and water was studied together with the description of the process of formation PPy/(f-)MWCNT hybrid materials via electrochemical co-deposition. The structural and morphological properties of the hybrids were characterized by Raman spectroscopy, scanning electron microscopy and atomic force microscopy revealing substantial differences among hybrid materials in their surface morphology and the influence of MWCNT functionalization on the orientation of growing PPy chains.

  1. Method for in situ determination cation exchange capacities of subsurface formations

    International Nuclear Information System (INIS)

    Fertl, W.H.; Welker, D.W.

    1980-01-01

    A method is disclosed for the in situ examination of each subsurface formation penetrated by a borehole to ascertain the cation exchange capacity of such formations within a geological region. Natural γ ray logging is used to develop signals functionally related to the total γ radiation and to the potassium-40, uranium and thorium energy-band radiations. A first borehole is traversed by a potential γ ray spectrometer to provide selected measurements of natural γ radiation. Core samples are taken from the logged formation and laboratory tests performed to determine the cation exchange capacity thereof. The cation exchange capacities thus are developed then correlated with selected parameters provided by the γ ray spectrometer to establish functional relationships. Cation exchange capacities of formations in subsequent boreholes within the region are then determined in situ by use of the natural γ ray spectrometer and these established relationships. (author)

  2. Demographic and Parenting Correlates of Adolescent Sleep Functioning.

    Science.gov (United States)

    Zapata Roblyer, Martha I; Grzywacz, Joseph G

    2015-11-01

    Despite the importance of parenting practices for adolescent adjustment, parenting correlates of adolescent sleep functioning remain understudied. This study delineated patterns of sleep functioning in a sample of ethnically diverse, low-income, adolescents and examined associations among three types of parenting practices (parental involvement, parent-child conflict, and parental control) and adolescent sleep functioning (difficulties initiating sleep and maintaining sleep, and sleep duration). Adolescents ( N = 91, 11-19 years old) self-reported on sleep functioning and parenting practices. Results showed that in the preceding month, 60.5% of adolescents had difficulties initiating sleep and 73.6% had difficulties maintaining sleep. Most adolescents slept 8 or more hours per night, but 30.7% slept less than 8 hours. Latino adolescents slept longer and had fewer difficulties maintaining sleep than non-Latino. High school students had fewer difficulties maintaining sleep than their middle school counterparts; conversely, older adolescents experienced shorter sleep duration than younger ones. Adolescents whose parents had post-secondary education had shorter sleep duration than those whose parents had not graduated from high school. Parental control was correlated with fewer difficulties initiating sleep, whereas parent-child conflict was correlated with more difficulties maintaining sleep. There were no parenting correlates of sleep duration. Latino adolescents had better sleep profiles than non-Latino ones. Regression analyses showed that parental control and parent-child conflict were associated with adolescent sleep functioning across ethnicities. Results suggest that parenting practices, as well as demographic characteristics, are associated with adolescent sleep functioning and should be taken into account in interventions aimed at improving sleep functioning among adolescents.

  3. Condensed phase QM/MM simulations utilizing the exchange core functions to describe exchange repulsions at the QM boundary region

    International Nuclear Information System (INIS)

    Umino, Satoru; Takahashi, Hideaki; Morita, Akihiro

    2016-01-01

    In a recent work, we developed a method [H. Takahashi et al., J. Chem. Phys. 143, 084104 (2015)] referred to as exchange-core function (ECF) approach, to compute exchange repulsion E ex between solute and solvent in the framework of the quantum mechanical (QM)/molecular mechanical (MM) method. The ECF, represented with a Slater function, plays an essential role in determining E ex on the basis of the overlap model. In the work of Takahashi et al. [J. Chem. Phys. 143, 084104 (2015)], it was demonstrated that our approach is successful in computing the hydrogen bond energies of minimal QM/MM systems including a cationic QM solute. We provide in this paper the extension of the ECF approach to the free energy calculation in condensed phase QM/MM systems by combining the ECF and the QM/MM-ER approach [H. Takahashi et al., J. Chem. Phys. 121, 3989 (2004)]. By virtue of the theory of solutions in energy representation, the free energy contribution δμ ex from the exchange repulsion was naturally formulated. We found that the ECF approach in combination with QM/MM-ER gives a substantial improvement on the calculation of the hydration free energy of a hydronium ion. This can be attributed to the fact that the ECF reasonably realizes the contraction of the electron density of the cation due to the deficit of an electron.

  4. Elucidation of spin echo small angle neutron scattering correlation functions through model studies.

    Science.gov (United States)

    Shew, Chwen-Yang; Chen, Wei-Ren

    2012-02-14

    Several single-modal Debye correlation functions to approximate part of the overall Debey correlation function of liquids are closely examined for elucidating their behavior in the corresponding spin echo small angle neutron scattering (SESANS) correlation functions. We find that the maximum length scale of a Debye correlation function is identical to that of its SESANS correlation function. For discrete Debye correlation functions, the peak of SESANS correlation function emerges at their first discrete point, whereas for continuous Debye correlation functions with greater width, the peak position shifts to a greater value. In both cases, the intensity and shape of the peak of the SESANS correlation function are determined by the width of the Debye correlation functions. Furthermore, we mimic the intramolecular and intermolecular Debye correlation functions of liquids composed of interacting particles based on a simple model to elucidate their competition in the SESANS correlation function. Our calculations show that the first local minimum of a SESANS correlation function can be negative and positive. By adjusting the spatial distribution of the intermolecular Debye function in the model, the calculated SESANS spectra exhibit the profile consistent with that of hard-sphere and sticky-hard-sphere liquids predicted by more sophisticated liquid state theory and computer simulation. © 2012 American Institute of Physics

  5. Correlation between hypertension and cognitive function in elderly

    Science.gov (United States)

    Fitri, F. I.; Rambe, A. S.

    2018-03-01

    Hypertension and cognitive impairment are common disorders among elderly adults, and their prevalences tend to rise as the population ages. This study aimed to determine the correlation between hypertension and cognitive function in elderly. It was a cross-sectional study involving 62 elderly subjects. All subjects underwent physical and neurologic examination and Montreal Cognitive Assessment-Indonesian Version (MoCA-INA) to assess cognitive function. This study included 62 subjects consisted of 26 males (41.9%) and 36 females (58.1%). There were 24 subjects (38.2%) with hypertension and 38 (61.3%) normal elderly subjects. The mean age was 65.71±4.49 years old. There were no significant differences in demographic characteristics, total MoCA-INA scores, and scores based on cognitive domains between two groups, except for visuospatial and executive function (p=0.026). There was a significant correlation between hypertension and visuospatial and executive function (r=0.301, p=0.017). Hypertension is correlated with cognitive impairment mainly on visuospatial and executive function in elderly.

  6. A non-JKL density matrix functional for intergeminal correlation between closed-shell geminals from analysis of natural orbital configuration interaction expansions.

    Science.gov (United States)

    van Meer, R; Gritsenko, O V; Baerends, E J

    2018-03-14

    Almost all functionals that are currently used in density matrix functional theory have been created by some a priori ansatz that generates approximations to the second-order reduced density matrix (2RDM). In this paper, a more consistent approach is used: we analyze the 2RDMs (in the natural orbital basis) of rather accurate multi-reference configuration interaction expansions for several small molecules (CH 4 , NH 3 , H 2 O, FH, and N 2 ) and use the knowledge gained to generate new functionals. The analysis shows that a geminal-like structure is present in the 2RDMs, even though no geminal theory has been applied from the onset. It is also shown that the leading non-geminal dynamical correlation contributions are generated by a specific set of double excitations. The corresponding determinants give rise to non-JKL (non Coulomb/Exchange like) multipole-multipole dispersive attractive terms between geminals. Due to the proximity of the geminals, these dispersion terms are large and cannot be omitted, proving pure JKL functionals to be essentially deficient. A second correction emerges from the observation that the "normal" geminal-like exchange between geminals breaks down when one breaks multiple bonds. This problem can be fixed by doubling the exchange between bond broken geminals, effectively restoring the often physically correct high-spin configurations on the bond broken fragments. Both of these corrections have been added to the commonly used antisymmetrized product of strongly orthogonal geminals functional. The resulting non-JKL functional Extended Löwdin-Shull Dynamical-Multibond is capable of reproducing complete active space self-consistent field curves, in which one active orbital is used for each valence electron.

  7. A non-JKL density matrix functional for intergeminal correlation between closed-shell geminals from analysis of natural orbital configuration interaction expansions

    Science.gov (United States)

    van Meer, R.; Gritsenko, O. V.; Baerends, E. J.

    2018-03-01

    Almost all functionals that are currently used in density matrix functional theory have been created by some a priori ansatz that generates approximations to the second-order reduced density matrix (2RDM). In this paper, a more consistent approach is used: we analyze the 2RDMs (in the natural orbital basis) of rather accurate multi-reference configuration interaction expansions for several small molecules (CH4, NH3, H2O, FH, and N2) and use the knowledge gained to generate new functionals. The analysis shows that a geminal-like structure is present in the 2RDMs, even though no geminal theory has been applied from the onset. It is also shown that the leading non-geminal dynamical correlation contributions are generated by a specific set of double excitations. The corresponding determinants give rise to non-JKL (non Coulomb/Exchange like) multipole-multipole dispersive attractive terms between geminals. Due to the proximity of the geminals, these dispersion terms are large and cannot be omitted, proving pure JKL functionals to be essentially deficient. A second correction emerges from the observation that the "normal" geminal-like exchange between geminals breaks down when one breaks multiple bonds. This problem can be fixed by doubling the exchange between bond broken geminals, effectively restoring the often physically correct high-spin configurations on the bond broken fragments. Both of these corrections have been added to the commonly used antisymmetrized product of strongly orthogonal geminals functional. The resulting non-JKL functional Extended Löwdin-Shull Dynamical-Multibond is capable of reproducing complete active space self-consistent field curves, in which one active orbital is used for each valence electron.

  8. Scanning, non-contact, hybrid broadband diffuse optical spectroscopy and diffuse correlation spectroscopy system.

    Science.gov (United States)

    Johansson, Johannes D; Mireles, Miguel; Morales-Dalmau, Jordi; Farzam, Parisa; Martínez-Lozano, Mar; Casanovas, Oriol; Durduran, Turgut

    2016-02-01

    A scanning system for small animal imaging using non-contact, hybrid broadband diffuse optical spectroscopy (ncDOS) and diffuse correlation spectroscopy (ncDCS) is presented. The ncDOS uses a two-dimensional spectrophotometer retrieving broadband (610-900 nm) spectral information from up to fifty-seven source-detector distances between 2 and 5 mm. The ncDCS data is simultaneously acquired from four source-detector pairs. The sample is scanned in two dimensions while tracking variations in height. The system has been validated with liquid phantoms, demonstrated in vivo on a human fingertip during an arm cuff occlusion and on a group of mice with xenoimplanted renal cell carcinoma.

  9. Principle, function, experiences, hybrid chilled ceilings; Prinzip, Funktion, Erfahrungen. Hybrid-Kuehldecken

    Energy Technology Data Exchange (ETDEWEB)

    Schulz, Uwe W. [Hochschule Luzern (Switzerland). Technik und Architektur

    2010-12-15

    Hybrid chilled ceilings combine a radiation chilled ceiling with thermal activations of a concrete ceiling. The activation permits the utilization of alternative and/or small cold generators for the efficient night cooling. The traditional chilled ceiling grants a speedy reaction to load variations as well as a reduction of the reverberation periods. In addition, the combination supplies a draught-free insertion of air. Beside established solutions, MWH Barcol-Air (Staefa, Switzerland) also offers project-specific hybrid chilled ceilings.

  10. Toward the Prediction of Water Exchange Rates in Magnetic Resonance Imaging Contrast Agents: A Density Functional Theory Study.

    Science.gov (United States)

    Regueiro-Figueroa, Martín; Platas-Iglesias, Carlos

    2015-06-18

    We present a theoretical investigation of Gd-Owater bonds in different complexes relevant as contrast agents in magnetic resonance imaging (MRI). The analysis of the Ln-Owater distances, electron density (ρBCP), and electron localization function (ELF) at the bond critical points of [Ln(DOTA)(H2O)](-) and [Ln(DTPA-BMA)(H2O)] indicates that the strength of the Ln-Owater bonds follows the order DTPA-BMA > DOTA (M isomer) > DOTA (m isomer). The ELF values decrease along the 4f period as the Ln-Owater bonds get shorter, in line with the labile capping bond phenomenon. Extension of these calculations to other Gd(3+) complexes allowed us to correlate the experimentally observed water exchange rates and the calculated ρBCP and ELF values. The water exchange reaction becomes faster as the Gd-Owater bonds are weakened, which is reflected in longer bond distances and lower values of ρBCP and ELF. DKH2 calculations show that the two coordinated water molecules may also have significantly different (17)O hyperfine coupling constants (HFCCs).

  11. Correlated electron dynamics and memory in time-dependent density functional theory

    International Nuclear Information System (INIS)

    Thiele, Mark

    2009-01-01

    Time-dependent density functional theory (TDDFT) is an exact reformulation of the time-dependent many-electron Schroedinger equation, where the problem of many interacting electrons is mapped onto the Kohn-Sham system of noninteracting particles which reproduces the exact electronic density. In the Kohn-Sham system all non-classical many-body effects are incorporated in the exchange-correlation potential which is in general unknown and needs to be approximated. It is the goal of this thesis to investigate the connection between memory effects and correlated electron dynamics in strong and weak fields. To this end one-dimensional two-electron singlet systems are studied. At the same time these systems include the onedimensional helium atom model, which is an established system to investigate the crucial effects of correlated electron dynamics in external fields. The studies presented in this thesis show that memory effects are negligible for typical strong field processes. Here the approximation of the spatial nonlocality is of primary importance. For the photoabsorption spectra on the other hand the neglect of memory effects leads to qualitative and quantitative errors, which are shown to be connected to transitions of double excitation character. To develop a better understanding of the conditions under which memory effects become important quantum fluid dynamics has been found to be especially suitable. It represents a further exact reformulation of the quantum mechanic many-body problem which is based on hydrodynamic quantities such as density and velocity. Memory effects are shown to be important whenever the velocity field develops strong gradients and dissipative effects contribute. (orig.)

  12. Correlated electron dynamics and memory in time-dependent density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Thiele, Mark

    2009-07-28

    Time-dependent density functional theory (TDDFT) is an exact reformulation of the time-dependent many-electron Schroedinger equation, where the problem of many interacting electrons is mapped onto the Kohn-Sham system of noninteracting particles which reproduces the exact electronic density. In the Kohn-Sham system all non-classical many-body effects are incorporated in the exchange-correlation potential which is in general unknown and needs to be approximated. It is the goal of this thesis to investigate the connection between memory effects and correlated electron dynamics in strong and weak fields. To this end one-dimensional two-electron singlet systems are studied. At the same time these systems include the onedimensional helium atom model, which is an established system to investigate the crucial effects of correlated electron dynamics in external fields. The studies presented in this thesis show that memory effects are negligible for typical strong field processes. Here the approximation of the spatial nonlocality is of primary importance. For the photoabsorption spectra on the other hand the neglect of memory effects leads to qualitative and quantitative errors, which are shown to be connected to transitions of double excitation character. To develop a better understanding of the conditions under which memory effects become important quantum fluid dynamics has been found to be especially suitable. It represents a further exact reformulation of the quantum mechanic many-body problem which is based on hydrodynamic quantities such as density and velocity. Memory effects are shown to be important whenever the velocity field develops strong gradients and dissipative effects contribute. (orig.)

  13. Coulomb holes and correlation potentials in the helium atom

    International Nuclear Information System (INIS)

    Slamet, M.; Sahni, V.

    1995-01-01

    Thus, the asymptotic structure of the exchange-correlation potential W xc (r) of the work formalism is that of W x (r) which is (-1/r). We also detemine via the Kinoshita wave function the correlation potential μ c (r) of Kohn-Sham theory, which differs from W c (r) in that it also incorporates the effects of the correlation contribution to the kinetic energy. Consequently, it is less attractive than W c (r), but also has zero slope at the nucleus. However, as is known, the potential μ c (r) is nonmonotonic, since it goes positive within the atom, then becomes negative in the classically forbidden region, finally vanishing asymptotically as a negative function. Since the exchange potentials of the work formalism and Kohn-Sham theory are the same for this atom, and because W c (r) is strictly representative of Coulomb correlations, we attribute the nonmonotonicity and positiveness of the Kohn-Sham potential μ c (r) to the correlation kinetic energy. This conclusion is consistent with the result that the difference between the correlation energies determined within the work formalism from the dynamic Coulomb hole and Kohn-Sham theory is equal to the correlation contribution to the kinetic energy

  14. Correlation functions of warped CFT

    Science.gov (United States)

    Song, Wei; Xu, Jianfei

    2018-04-01

    Warped conformal field theory (WCFT) is a two dimensional quantum field theory whose local symmetry algebra consists of a Virasoro algebra and a U(1) Kac-Moody algebra. In this paper, we study correlation functions for primary operators in WCFT. Similar to conformal symmetry, warped conformal symmetry is very constraining. The form of the two and three point functions are determined by the global warped conformal symmetry while the four point functions can be determined up to an arbitrary function of the cross ratio. The warped conformal bootstrap equation are constructed by formulating the notion of crossing symmetry. In the large central charge limit, four point functions can be decomposed into global warped conformal blocks, which can be solved exactly. Furthermore, we revisit the scattering problem in warped AdS spacetime (WAdS), and give a prescription on how to match the bulk result to a WCFT retarded Green's function. Our result is consistent with the conjectured holographic dualities between WCFT and WAdS.

  15. Correlation Functions in Holographic Minimal Models

    CERN Document Server

    Papadodimas, Kyriakos

    2012-01-01

    We compute exact three and four point functions in the W_N minimal models that were recently conjectured to be dual to a higher spin theory in AdS_3. The boundary theory has a large number of light operators that are not only invisible in the bulk but grow exponentially with N even at small conformal dimensions. Nevertheless, we provide evidence that this theory can be understood in a 1/N expansion since our correlators look like free-field correlators corrected by a power series in 1/N . However, on examining these corrections we find that the four point function of the two bulk scalar fields is corrected at leading order in 1/N through the contribution of one of the additional light operators in an OPE channel. This suggests that, to correctly reproduce even tree-level correlators on the boundary, the bulk theory needs to be modified by the inclusion of additional fields. As a technical by-product of our analysis, we describe two separate methods -- including a Coulomb gas type free-field formalism -- that ...

  16. The resilient hybrid fiber sensor network with self-healing function

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Shibo, E-mail: Shibo-Xu@tju.edu.cn; Liu, Tiegen; Ge, Chunfeng; Chen, Qinnan; Zhang, Hongxia [College of Precision Instrument and Opto-electronics Engineering, Tianjin University, Tianjin 300072 (China); Key Laboratory of Opto-electronics Information Technology (Tianjin University), Ministry of Education, Tianjin 300072 (China)

    2015-03-15

    This paper presents a novel resilient fiber sensor network (FSN) with multi-ring architecture, which could interconnect various kinds of fiber sensors responsible for more than one measurands. We explain how the intelligent control system provides sensors with self-healing function meanwhile sensors are working properly, besides each fiber in FSN is under real-time monitoring. We explain the software process and emergency mechanism to respond failures or other circumstances. To improve the efficiency in the use of limited spectrum resources in some situations, we have two different structures to distribute the light sources rationally. Then, we propose a hybrid sensor working in FSN which is a combination of a distributed sensor and a FBG (Fiber Bragg Grating) array fused in a common fiber sensing temperature and vibrations simultaneously with neglectable crosstalk to each other. By making a failure to a working fiber in experiment, the feasibility and effectiveness of the network with a hybrid sensor has been demonstrated, hybrid sensors could not only work as designed but also survive from destructive failures with the help of resilient network and smart and quick self-healing actions. The network has improved the viability of the fiber sensors and diversity of measurands.

  17. The resilient hybrid fiber sensor network with self-healing function

    Science.gov (United States)

    Xu, Shibo; Liu, Tiegen; Ge, Chunfeng; Chen, Qinnan; Zhang, Hongxia

    2015-03-01

    This paper presents a novel resilient fiber sensor network (FSN) with multi-ring architecture, which could interconnect various kinds of fiber sensors responsible for more than one measurands. We explain how the intelligent control system provides sensors with self-healing function meanwhile sensors are working properly, besides each fiber in FSN is under real-time monitoring. We explain the software process and emergency mechanism to respond failures or other circumstances. To improve the efficiency in the use of limited spectrum resources in some situations, we have two different structures to distribute the light sources rationally. Then, we propose a hybrid sensor working in FSN which is a combination of a distributed sensor and a FBG (Fiber Bragg Grating) array fused in a common fiber sensing temperature and vibrations simultaneously with neglectable crosstalk to each other. By making a failure to a working fiber in experiment, the feasibility and effectiveness of the network with a hybrid sensor has been demonstrated, hybrid sensors could not only work as designed but also survive from destructive failures with the help of resilient network and smart and quick self-healing actions. The network has improved the viability of the fiber sensors and diversity of measurands.

  18. The resilient hybrid fiber sensor network with self-healing function

    International Nuclear Information System (INIS)

    Xu, Shibo; Liu, Tiegen; Ge, Chunfeng; Chen, Qinnan; Zhang, Hongxia

    2015-01-01

    This paper presents a novel resilient fiber sensor network (FSN) with multi-ring architecture, which could interconnect various kinds of fiber sensors responsible for more than one measurands. We explain how the intelligent control system provides sensors with self-healing function meanwhile sensors are working properly, besides each fiber in FSN is under real-time monitoring. We explain the software process and emergency mechanism to respond failures or other circumstances. To improve the efficiency in the use of limited spectrum resources in some situations, we have two different structures to distribute the light sources rationally. Then, we propose a hybrid sensor working in FSN which is a combination of a distributed sensor and a FBG (Fiber Bragg Grating) array fused in a common fiber sensing temperature and vibrations simultaneously with neglectable crosstalk to each other. By making a failure to a working fiber in experiment, the feasibility and effectiveness of the network with a hybrid sensor has been demonstrated, hybrid sensors could not only work as designed but also survive from destructive failures with the help of resilient network and smart and quick self-healing actions. The network has improved the viability of the fiber sensors and diversity of measurands

  19. Hybrid functional band gap calculation of SnO{sub 6} containing perovskites and their derived structures

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyewon [Department of Physics, Pusan National University, Pusan 609-735, Republic of South Korea (Korea, Republic of); Cheong, S.W. [Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854 (United States); Kim, Bog G., E-mail: boggikim@pusan.ac.kr [Department of Physics, Pusan National University, Pusan 609-735, Republic of South Korea (Korea, Republic of)

    2015-08-15

    We have studied the properties of SnO{sub 6} octahedra-containing perovskites and their derived structures using ab initio calculations with different density functionals. In order to predict the correct band gap of the materials, we have used B3LYP hybrid density functional, and the results of B3LYP were compared with those obtained using the local density approximation and generalized gradient approximation data. The calculations have been conducted for the orthorhombic ground state of the SnO{sub 6} containing perovskites. We also have expended the hybrid density functional calculation to the ASnO{sub 3}/A'SnO{sub 3} system with different cation orderings. We propose an empirical relationship between the tolerance factor and the band gap of SnO{sub 6} containing oxide materials based on first principles calculation. - Graphical abstract: (a) Structure of ASnO{sub 3} for orthorhombic ground state. The green ball is A (Ba, Sr, Ca) cation and the small (red) ball on edge is oxygen. SnO{sub 6} octahedrons are plotted as polyhedron. (b) Band gap of ASnO{sub 3} as a function of the tolerance factor for different density functionals. The experimental values of the band gap are marked as green pentagons. (c) ASnO{sub 3}/A'SnO{sub 3} superlattices with two types cation arrangement: [001] layered structure and [111] rocksalt structure, respectively. (d) B3LYP hybrid functional band gaps of ASnO{sub 3}, [001] ordered superlattices, and [111] ordered superlattices of ASnO{sub 3}/A'SnO{sub 3} as a function of the effective tolerance factor. Note the empirical linear relationship between the band gap and effective tolerance factor. - Highlights: • We report the hybrid functional band gap calculation of ASnO{sub 3} and ASnO{sub 3}/A'SnO{sub 3}. • The band gap of ASnO{sub 3} using B3LYP functional reproduces the experimental value. • We propose the linear relationship between the tolerance factor and the band gap.

  20. First-order-reversal-curve analysis of exchange-coupled SmCo/NdFeB nanocomposite alloys

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Mingxiang; Zhang, Pengyue, E-mail: Zhang_pengyue@cjlu.edu.cn; Ge, Hongliang; Yu, Nengjun; Wu, Qiong

    2014-06-01

    Exchange-coupled SmCo{sub 5}/Nd{sub 2}Fe{sub 14}B nanocomposite magnets have been fabricated by ball milling of the micrometer sized SmCo{sub 5} and Nd{sub 2}Fe{sub 14}B powders. The influence of Nd{sub 2}Fe{sub 14}B content on the microstructure and magnetic properties of these hybrid alloys was investigated. The alloys that show strong intergrain exchange-coupling behavior with (BH){sub max}=2.95 MGOe was obtained when the two hard phases are well coupled. A first-order-reversal-curve (FORC) analysis was performed for both SmCo{sub 5} single-phase magnet and SmCo{sub 5}/Nd{sub 2}Fe{sub 14}B hybrid magnet; the FORC diagrams results show two major peaks for the hybrid magnets. In both cases, the magnetization reversal behaviors for these alloys were discussed in detail and are consistent with the results of δM plots. - Highlights: • Exchange-coupled SmCo{sub 5}/Nd{sub 2}Fe{sub 14}B nanocomposite magnets were studied. • Magnetization reversal behaviors of the hybrid magnet were discussed. • The FORCs analysis is taken to identify the optimal conditions for hybrid magnet.