D., I. Bilc; R., Orlando; R., Shaltaf; G., M. Rignanese; J., Íñiguez; Ph., Ghosez
2008-01-01
Using a linear combination of atomic orbitals approach, we report a systematic comparison of various Density Functional Theory (DFT) and hybrid exchange-correlation functionals for the prediction of the electronic and structural properties of prototypical ferroelectric oxides. It is found that none of the available functionals is able to provide, at the same time, accurate electronic and structural properties of the cubic and tetragonal phases of BaTiO$_3$ and PbTiO$_3$. Some, although not al...
Asymptotic Correction Schemes for Semilocal Exchange-Correlation Functionals
Pan, Chi-Ruei; Chai, Jeng-Da
2013-01-01
Aiming to remedy the incorrect asymptotic behavior of conventional semilocal exchange-correlation (XC) density functionals for finite systems, we propose an asymptotic correction scheme, wherein an exchange density functional whose functional derivative has the correct (-1/r) asymptote can be directly added to any semilocal density functional. In contrast to semilocal approximations, our resulting exchange kernel in reciprocal space exhibits the desirable singularity of the type O(-1/q^2) as q -> 0, which is a necessary feature for describing the excitonic effects in non-metallic solids. By applying this scheme to a popular semilocal density functional, PBE [J. P. Perdew, K. Burke, and M. Ernzerhof, Phys. Rev. Lett. 77, 3865 (1996)], the predictions of the properties that are sensitive to the asymptote are significantly improved, while the predictions of the properties that are insensitive to the asymptote remain essentially the same as PBE. Relative to the popular model XC potential scheme, our scheme is sig...
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...... generally applicable models; a robust MM-estimator loss function, for ensuring resistance to outliers in data; and a hierarchical bootstrap resampling estimating prediction error validation method, for selecting the model complexity that provide best transferability outside the training data. Three new semi...... on accurate and efficient approximations to the exchange correlation functional, yet these functional approximations have lacked a systematic way to estimate the underlying uncertainties. A Bayesian error estimation approach provides a mechanism for calculating approximative uncertainties, and so accurate...
Exact Exchange-Correlation Functional for the Infinitely Stretched Hydrogen Molecule
Matito, Eduard; Lopez, Xabier; Ugalde, Jesus M
2016-01-01
The exchange-correlation hole density of the infinitely stretched (dissociated) hydrogen molecule can be cast into a closed analytical form by using its exact wave function. This permits to obtain an explicit exchange-correlation energy functional of the electron density which allows for its functional derivation to yield the corresponding Kohh-Sham effective exchange-correlation potential. We have shown that this exchange-correlation functional is exact for the dissociated hydrogen molecule, yields its dissociation energy correctly, and its corresponding exchange-correlation potential has the correct $-1/r$ asymptotic behavior.
Energy Technology Data Exchange (ETDEWEB)
Zhou, Yongxi; Ernzerhof, Matthias, E-mail: Matthias.Ernzerhof@UMontreal.ca [Département de Chimie, Université de Montréal, C.P. 6128, Succursale A, Montréal, Québec H3C 3J7 (Canada); Bahmann, Hilke [Department of Chemistry, Technische Universität Berlin, Strasse des 17 Juni, Berlin (Germany)
2015-09-28
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.
Yu, Haoyu S; Zhang, Wenjing; Verma, Pragya; He, Xiao; Truhlar, Donald G
2015-05-14
The goal of this work is to develop a gradient approximation to the exchange-correlation functional of Kohn-Sham density functional theory for treating molecular problems with a special emphasis on the prediction of quantities important for homogeneous catalysis and other molecular energetics. Our training and validation of exchange-correlation functionals is organized in terms of databases and subdatabases. The key properties required for homogeneous catalysis are main group bond energies (database MGBE137), transition metal bond energies (database TMBE32), reaction barrier heights (database BH76), and molecular structures (database MS10). We also consider 26 other databases, most of which are subdatabases of a newly extended broad database called Database 2015, which is presented in the present article and in its ESI. Based on the mathematical form of a nonseparable gradient approximation (NGA), as first employed in the N12 functional, we design a new functional by using Database 2015 and by adding smoothness constraints to the optimization of the functional. The resulting functional is called the gradient approximation for molecules, or GAM. The GAM functional gives better results for MGBE137, TMBE32, and BH76 than any available generalized gradient approximation (GGA) or than N12. The GAM functional also gives reasonable results for MS10 with an MUE of 0.018 Å. The GAM functional provides good results both within the training sets and outside the training sets. The convergence tests and the smooth curves of exchange-correlation enhancement factor as a function of the reduced density gradient show that the GAM functional is a smooth functional that should not lead to extra expense or instability in optimizations. NGAs, like GGAs, have the advantage over meta-GGAs and hybrid GGAs of respectively smaller grid-size requirements for integrations and lower costs for extended systems. These computational advantages combined with the relatively high accuracy for all
A generalized exchange-correlation functional: the Neural-Networks approach
Zheng, X; Wang, X J; Chen, G H; Zheng, Xiao; Hu, LiHong; Wang, XiuJun; Chen, GuanHua
2003-01-01
A Neural-Networks-based approach is proposed to construct a new type of exchange-correlation functional for density functional theory. It is applied to improve B3LYP functional by taking into account of high-order contributions to the exchange-correlation functional. The improved B3LYP functional is based on a neural network whose structure and synaptic weights are determined from 116 known experimental atomization energies, ionization potentials, proton affinities or total atomic energies which were used by Becke in his pioneer work on the hybrid functionals [J. Chem. Phys. ${\\bf 98}$, 5648 (1993)]. It leads to better agreement between the first-principles calculation results and these 116 experimental data. The new B3LYP functional is further tested by applying it to calculate the ionization potentials of 24 molecules of the G2 test set. The 6-311+G(3{\\it df},2{\\it p}) basis set is employed in the calculation, and the resulting root-mean-square error is reduced to 2.2 kcal$\\cdot$mol$^{-1}$ in comparison to ...
Patching the Exchange-Correlation Potential in Density Functional Theory.
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.
Quantum Monte Carlo Benchmark of Exchange-Correlation Functionals for Bulk Water.
Morales, Miguel A; Gergely, John R; McMinis, Jeremy; McMahon, Jeffrey M; Kim, Jeongnim; Ceperley, David M
2014-06-10
The accurate description of the thermodynamic and dynamical properties of liquid water from first-principles is a very important challenge to the theoretical community. This represents not only a critical test of the predictive capabilities of first-principles methods, but it will also shed light into the microscopic properties of such an important substance. Density Functional Theory, the main workhorse in the field of first-principles methods, has been so far unable to properly describe water and its unusual properties in the liquid state. With the recent introduction of exact exchange and an improved description of dispersion interaction, the possibility of an accurate description of the liquid is finally within reach. Unfortunately, there is still no way to systematically improve exchange-correlation functionals, and the number of available functionals is very large. In this article we use highly accurate quantum Monte Carlo calculations to benchmark a selection of exchange-correlation functionals typically used in Density Functional Theory simulations of bulk water. This allows us to test the predictive capabilities of these functionals in water, giving us a way to choose optimal functionals for first-principles simulations. We compare and contrast the importance of different features of functionals, including the hybrid component, the vdW component, and their importance within different aspects of the PES. In addition, in order to correct the inaccuracies in the description of short-range interactions in the liquid, we test a recently introduced scheme that combines Density Functional Theory with Coupled Cluster calculations through a Many-Body expansion of the energy.
Assessing Accuracy of Exchange-Correlation Functionals for the Description of Atomic Excited States
Makowski, Marcin; Hanas, Martyna
2016-09-01
The performance of exchange-correlation functionals for the description of atomic excitations is investigated. A benchmark set of excited states is constructed and experimental data is compared to Time-Dependent Density Functional Theory (TDDFT) calculations. The benchmark results show that for the selected group of functionals good accuracy may be achieved and the quality of predictions provided is competitive to computationally more demanding coupled-cluster approaches. Apart from testing the standard TDDFT approaches, also the role of self-interaction error plaguing DFT calculations and the adiabatic approximation to the exchange-correlation kernels is given some insight.
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...
Design of exchange-correlation functionals through the correlation factor approach
Energy Technology Data Exchange (ETDEWEB)
Pavlíková Přecechtělová, Jana, E-mail: j.precechtelova@gmail.com, E-mail: Matthias.Ernzerhof@UMontreal.ca [Département de Chimie, Université de Montréal, C.P. 6128 Succursale A, Montréal, Québec H3C 3J7 (Canada); Institut für Chemie, Theoretische Chemie / Quantenchemie, Sekr. C7, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin (Germany); Bahmann, Hilke; Kaupp, Martin [Institut für Chemie, Theoretische Chemie / Quantenchemie, Sekr. C7, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin (Germany); Ernzerhof, Matthias, E-mail: j.precechtelova@gmail.com, E-mail: Matthias.Ernzerhof@UMontreal.ca [Département de Chimie, Université de Montréal, C.P. 6128 Succursale A, Montréal, Québec H3C 3J7 (Canada)
2015-10-14
The correlation factor model is developed in which the spherically averaged exchange-correlation hole of Kohn-Sham theory is factorized into an exchange hole model and a correlation factor. The exchange hole model reproduces the exact exchange energy per particle. The correlation factor is constructed in such a manner that the exchange-correlation energy correctly reduces to exact exchange in the high density and rapidly varying limits. Four different correlation factor models are presented which satisfy varying sets of physical constraints. Three models are free from empirical adjustments to experimental data, while one correlation factor model draws on one empirical parameter. The correlation factor models are derived in detail and the resulting exchange-correlation holes are analyzed. Furthermore, the exchange-correlation energies obtained from the correlation factor models are employed to calculate total energies, atomization energies, and barrier heights. It is shown that accurate, non-empirical functionals can be constructed building on exact exchange. Avenues for further improvements are outlined as well.
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.
Exchange-correlation functionals via local interpolation along the adiabatic connection
Vuckovic, Stefan; Savin, Andreas; Teale, Andrew M; Gori-Giorgi, Paola
2016-01-01
The construction of density-functional approximations is explored by modeling the adiabatic connection em locally, using energy densities defined in terms of the electrostatic potential of the exchange-correlation hole. These local models are more amenable to the construction of size-consistent approximations than their global counterparts. In this work we use accurate input local ingredients to assess the accuracy of range of local interpolation models against accurate exchange-correlation energy densities. The importance of the strictly-correlated electrons (SCE) functional describing the strong coupling limit is emphasized, enabling the corresponding interpolated functionals to treat strong correlation effects. In addition to exploring the performance of such models numerically for the helium and beryllium isoelectronic series and the dissociation of the hydrogen molecule, an approximate analytic model is presented for the initial slope of the local adiabatic connection. Comparisons are made with approache...
Convexity and the translational-invariance constraint on the exchange-correlation functional
Joubert, Daniel; Levy, Mel
1996-07-01
Knowledge of the properties of the exchange-correlation functional in the form 1/λvxc([ρλ],r/λ), where ρλ(r)= λ3ρ(λr), is important when expressing the exchange-correlation energy as a line integral Exc[ρ]=∫10dλ∫dr1/λvxc([ρλ],r/λ) [3ρ(r)+r.∇ρ(r)] [R. van Leeuwen and E. J. Baerends, Phys. Rev. A 51, 170 (1995)]. With this in mind, it is shown that in the low-density limit limλ-->0∫ρ(r)∇21/λvxc([ρλ],r/λ)d3 r<=4π∫ρ(r)2d3r. This inequality is violated in the local-density approximation.
Aldegunde, Manuel; Kermode, James R.; Zabaras, Nicholas
2016-04-01
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.
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) unity (>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.
Exchange-correlation interaction and AO-hybridization of alkali-metal atomic clusters.
Liu, Xuan; Ito, Haruhiko; Torikai, Eiko
2013-09-19
The structure of alkali-metal atomic clusters is optimized with B3P86 hybrid functional for the highest spin state as well as with B3LYP hybrid functional for the lowest spin state. A dramatic change from plane to solid occurs in the highest spin state when the number of constituent atoms is four. The binding, exchange, and correlation energies are evaluated for both the highest and lowest spin states. Next, we explore the dependence of the exchange and correlation energies on the binding energy. The exchange energy contributes to the formation of the highest spin clusters, whereas the correlation energy contributes to the formation of the lowest spin clusters. The highest spin clusters are most stable when the exchange energy is a minimum. Then, to see why the ferromagnetic bond among spin-aligned identical atoms arises against Pauli exclusion principle, we estimate the mixing ratio of p orbitals in molecular orbitals. The s-p hybridization increases the binding energy in absolute value due to the extensive overlap of molecular orbitals and leads to generation of the highest spin clusters.
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.
Exchange-Correlation Effects for Noncovalent Interactions in Density Functional Theory.
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.
libvdwxc: a library for exchange-correlation functionals in the vdW-DF family
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.
Yao, Yi; Kanai, Yosuke
2017-06-01
We present the implementation and performance of the strongly constrained and appropriately normed, SCAN, meta-GGA exchange-correlation (XC) approximation in the planewave-pseudopotential (PW-PP) formalism using the Troullier-Martins pseudopotential scheme. We studied its performance by applying the PW-PP implementation to several practical applications of interest in condensed matter sciences: (a) crystalline silicon and germanium, (b) martensitic phase transition energetics of phosphorene, and (c) a single water molecule physisorption on a graphene sheet. Given the much-improved accuracy over the GGA functionals and its relatively low computational cost compared to hybrid XC functionals, the SCAN functional is highly promising for various practical applications of density functional theory calculations for condensed matter systems. At same time, the SCAN meta-GGA functional appears to require more careful attention to numerical details. The meta-GGA functional shows more significant dependence on the fast Fourier transform grid, which is used for evaluating the XC potential in real space in the PW-PP formalism, than other more conventional GGA functionals do. Additionally, using pseudopotentials that are generated at a different/lower level of XC approximation could introduce noticeable errors in calculating some properties such as phase transition energetics.
The effect of the exchange-correlation functional on H2 dissociation on Ru(0001)
Wijzenbroek, M.; Kroes, G. J.
2014-02-01
The specific reaction parameter (SRP) approach to density functional theory (DFT) has enabled a chemically accurate description of reactive scattering experiments for activated H2-metal systems (H2 + Cu(111) and Cu(100)), but its application has not yet resulted in a similarly accurate description of non-activated or weakly activated H2-metal systems. In this study, the effect of the choice of the exchange-correlation functional in DFT on the potential energy surface and dynamics of H2 dissociation on Ru(0001), a weakly activated system, is investigated. In total, full potential energy surfaces were calculated for over 20 different functionals. The functionals investigated include functionals incorporating an approximate description of the van der Waals dispersion in the correlation functional (vdW-DF and vdW-DF2 functionals), as well as the revTPSS meta-GGA. With two of the functionals investigated here, which include vdW-DF and vdW-DF2 correlation, it has been possible to accurately reproduce molecular beam experiments on sticking of H2 and D2, as these functionals yield a reaction probability curve with an appropriate energy width. Diffraction probabilities computed with these two functionals are however too high compared to experimental diffraction probabilities, which are extrapolated from surface temperatures (Ts) ⩾ 500 K to 0 K using a Debye-Waller model. Further research is needed to establish whether this constitutes a failure of the two candidate SRP functionals or a failure of the Debye-Waller model, the use of which can perhaps in future be avoided by performing calculations that include the effect of surface atom displacement or motion, and thereby of the experimental Ts.
Away from generalized gradient approximation: orbital-dependent exchange-correlation functionals.
Baerends, E J; Gritsenko, O V
2005-08-08
The local-density approximation of density functional theory (DFT) is remarkably accurate, for instance, for geometries and frequencies, and the generalized gradient approximations have also made bond energies quite reliable. Sometimes, however, one meets with failure in individual cases. One of the possible routes towards better functionals would be the incorporation of orbital dependence (which is an implicit density dependency) in the functionals. We discuss this approach both for energies and for response properties. One possibility is the use of the Hartree-Fock-type exchange energy expression as orbital-dependent functional. We will argue that in spite of the increasing popularity of this approach, it does not offer any advantage over Hartree-Fock for energies. We will advocate not to apply the separation of exchange and correlation, which is so ingrained in quantum chemistry, but to model both simultaneously. For response properties the energies and shapes of the virtual orbitals are crucial. We will discuss the benefits that Kohn-Sham potentials can offer which are derived from either an orbital-dependent energy functional, including the exact-exchange functional, or which can be obtained directly as orbital-dependent functional. We highlight the similarity of the Hartree-Fock and Kohn-Sham occupied orbitals and orbital energies, and the essentially different meanings the virtual orbitals and orbital energies have in these two models. We will show that these differences are beneficial for DFT in the case of localized excitations (in a small molecule or in a fragment), but are detrimental for charge-transfer excitations. Again, orbital dependency, in this case in the exchange-correlation kernel, offers a solution.
Current Density-Functional Theory using meta-Generalized Gradient Exchange--Correlation Functionals
Furness, James W; Tellgren, Erik I; Stopkowicz, Stella; Ekström, Ulf; Helgaker, Trygve; Teale, Andrew M
2015-01-01
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 non-perturbative implementation of these functionals is the ability to seamlessly explore a wide range of magnetic fields up to 1 a.u. ($\\sim 235000$T) in strength. CDFT functionals based on the TPSS and B98 forms are investigated and their performance is assessed by comparison with accurate CCSD(T) data. In the weak field regime magnetic properties such as magnetizabilities and NMR shielding constants show modest but systematic improvements over GGA functionals. However, in 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...
Current Density Functional Theory Using Meta-Generalized Gradient Exchange-Correlation Functionals.
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.
Charles, Nenian; Rondinelli, James M.
2016-11-01
Motivated by the resurgence of electronic and optical property design in ordered fluoride and oxyfluoride compounds, we present a density functional theory (DFT) study of 19 materials with structures, ranging from simple to complex, and variable oxygen-to-fluorine ratios. We focus on understanding the accuracy of the exchange-correlation potentials (Vx c) to DFT for the prediction of structural, electronic, and lattice dynamical properties at four different levels of theory, i.e., the local density approximation (LDA), generalized gradient approximation (GGA), metaGGA, and hybrid functional level which includes fractions of exact exchange. We investigate in detail the metaGGA functionals MS2 [Sun et al., Phys. Rev. Lett. 111, 106401 (2013), 10.1103/PhysRevLett.111.106401] and SCAN [Sun et al., Phys. Rev. Lett. 115, 036402 (2015), 10.1103/PhysRevLett.115.036402], and show that although the metaGGAs show improvements over the LDA and GGA functionals in describing the electronic structure and phonon frequencies, the static structural properties of fluorides and oxyfluorides are often more accurately predicted by the GGA-level Perdew-Burke-Ernzerhof functional for solids, PBEsol. Results from LDA calculations are unsatisfactory for any compound, regardless of oxygen concentration. The PBEsol and Heyd-Scuseria-Ernzerhof (HSE06) functionals give good performance in all-oxide or all-fluoride compounds. For the oxyfluorides, PBEsol is consistently more accurate for structural properties across all oxygen concentrations; however, we stress the need for detailed property assessment with various functionals for oxyfluorides with variable composition. The "best" functional is anticipated to be more strongly dependent on the property of interest. Our study provides useful insights in selecting an Vx c that achieves optimal performance compromises, enabling more accurate predictive design of functional fluoride-based materials with density functional theory.
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
Laplacian-level density functionals for the kinetic energy density and exchange-correlation energy
Perdew, John P.; Constantin, Lucian A.
2007-04-01
We construct a Laplacian-level meta-generalized-gradient-approximation (meta-GGA) for the noninteracting (Kohn-Sham orbital) positive kinetic energy density τ of an electronic ground state of density n . This meta-GGA is designed to recover the fourth-order gradient expansion τGE4 in the appropriate slowly varying limit and the von Weizsäcker expression τW=∣∇n∣2/(8n) in the rapidly varying limit. It is constrained to satisfy the rigorous lower bound τW(r)⩽τ(r) . Our meta-GGA is typically a strong improvement over the gradient expansion of τ for atoms, spherical jellium clusters, jellium surfaces, the Airy gas, Hooke’s atom, one-electron Gaussian density, quasi-two-dimensional electron gas, and nonuniformly scaled hydrogen atom. We also construct a Laplacian-level meta-GGA for exchange and correlation by employing our approximate τ in the Tao-Perdew-Staroverov-Scuseria (TPSS) meta-GGA density functional. The Laplacian-level TPSS gives almost the same exchange-correlation enhancement factors and energies as the full TPSS, suggesting that τ and ∇2n carry about the same information beyond that carried by n and ∇n . Our kinetic energy density integrates to an orbital-free kinetic energy functional that is about as accurate as the fourth-order gradient expansion for many real densities (with noticeable improvement in molecular atomization energies), but considerably more accurate for rapidly varying ones.
Borgoo, Alex; Teale, Andrew M; Tozer, David J
2012-01-21
Correlated electron densities, experimental ionisation potentials, and experimental electron affinities are used to investigate the homogeneity of the exchange-correlation and non-interacting kinetic energy functionals of Kohn-Sham density functional theory under density scaling. Results are presented for atoms and small molecules, paying attention to the influence of the integer discontinuity and the choice of the electron affinity. For the exchange-correlation functional, effective homogeneities are highly system-dependent on either side of the integer discontinuity. By contrast, the average homogeneity-associated with the potential that averages over the discontinuity-is generally close to 4/3 when the discontinuity is computed using positive affinities for systems that do bind an excess electron and negative affinities for those that do not. The proximity to 4/3 becomes increasingly pronounced with increasing atomic number. Evaluating the discontinuity using a zero affinity in systems that do not bind an excess electron instead leads to effective homogeneities on the electron abundant side that are close to 4/3. For the non-interacting kinetic energy functional, the effective homogeneities are less system-dependent and the effect of the integer discontinuity is less pronounced. Average values are uniformly below 5/3. The study provides information that may aid the development of improved exchange-correlation and non-interacting kinetic energy functionals. © 2012 American Institute of Physics
Energy Technology Data Exchange (ETDEWEB)
Clay, Raymond C. [Univ. of Illinois, Urbana, IL (United States); Mcminis, Jeremy [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); McMahon, Jeffrey M. [Univ. of Illinois, Urbana, IL (United States); Pierleoni, Carlo [Istituto Nazionale di Fisica Nucleare (INFN), L' aquila (Italy). Lab. Nazionali del Gran Sasso (INFN-LNGS); Ceperley, David M. [Univ. of Illinois, Urbana, IL (United States); Morales, Miguel A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2014-05-01
The ab initio phase diagram of dense hydrogen is very sensitive to errors in the treatment of electronic correlation. Recently, it has been shown that the choice of the density functional has a large effect on the predicted location of both the liquid-liquid phase transition and the solid insulator-to-metal transition in dense hydrogen. To identify the most accurate functional for dense hydrogen applications, we systematically benchmark some of the most commonly used functionals using quantum Monte Carlo. By considering several measures of functional accuracy, we conclude that the van der Waals and hybrid functionals significantly outperform local density approximation and Perdew-Burke-Ernzerhof. We support these conclusions by analyzing the impact of functional choice on structural optimization in the molecular solid, and on the location of the liquid-liquid phase transition.
Constantin, L A; Della Sala, F
2013-01-01
Using a reverse-engineering method we construct a meta-generalized gradient approximation (meta-GGA) angle-averaged exchange-correlation hole model which has a general applicability. It satisfies known exact hole constraints and can exactly recover the exchange-correlation energy density of any reasonable meta-GGA exchange-correlation energy functional satisfying a minimal set of exact properties. The hole model is applied to several non-empirical meta-GGA functionals: the Tao-Perdew-Staroverov-Scuseria (TPSS), the revised TPSS (revTPSS) and the recently Balanced LOCalization (BLOC) meta-GGA of L.A. Constantin, E. Fabiano, and F. Della Sala, (J. Chem. Theory Comput. 9, 2256 (2013)). The empirical M06-L meta-GGA functional is also considered. Real-space analyses of atoms and ions as well as wave-vector analyses of jellium surface energies, show that the meta-GGA hole models, in particular the BLOC one, are very realistic and can reproduce many features of benchmark XC holes. In addition, the BLOC hole model ca...
Santra, Biswajit; Klimeš, Jiří; Tkatchenko, Alexandre; Alfè, Dario; Slater, Ben; Michaelides, Angelos; Car, Roberto; Scheffler, Matthias
2013-10-01
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.
Energy Technology Data Exchange (ETDEWEB)
Segala, Maximiliano [Universidade Estadual do Rio Grande do Sul, Rua Oscar Matzembacher 475, 96760-000, Tapes, RS (Brazil); Chong, Delano P. [Department of Chemistry, 2036 Main Mall, University of British Columbia, Vancouver, B.C., V6T 1Z1 (Canada)], E-mail: chong@chem.ubc.ca
2009-04-15
In this paper, ionization energies of gas-phase atoms and molecules are calculated by energy-difference method and by approximate transition-state models with density functional theory (DFT). To determine the best functionals for ionization energies, we first study the H to Ar atoms. An approximation is used in which the electron density is first obtained from Kohn-Sham computations with an exchange-correlation potential V{sub xc} known as statistical average of orbital potentials (SAOP), after which the energy is computed from that density with 59 different exchange-correlation energy functionals E{sub xc}. For the 18 atoms, the best E{sub xc} functional providing an average absolute deviation (AAD) of only 0.110 eV is one known as the Krieger-Chen-Iafrate-Savin functional modified by Krieger, Chen, Iafrate, and Kurth, if one uses the spin-polarized spherical atom description. On the other hand, if one imposes the condition of integer-electrons, the best functional is the Becke 1997 functional modified by Wilson, Bradley, and Tozer, with an AAD of 0.107 eV, while several other functionals perform almost as well. For molecules, we can achieve an accuracy of AAD = 0.21 eV for valence VIPs of nonperhalo molecules with {delta}E(V{sub xc} = SAOP;PBE0) using integer-electron description. For perhalo molecules our best approach is {delta}E(V{sub xc} from either E{sub xc} or SAOP;mPW1PW) with full symmetry to obtain an AAD = 0.24 eV.
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)
Holas, A; March, N H; Rubio, Angel
2005-11-15
Holas and March [Phys. Rev. A. 51, 2040 (1995)] gave a formally exact theory for the exchange-correlation (xc) force F(xc)(r)= -inverted Deltaupsilon(xc)(r) associated with the xc potential upsilon(xc)(r) of the density-functional theory in terms of low-order density matrices. This is shown in the present study to lead, rather directly, to the determination of a sum rule nF(xc)=0 relating the xc force with the ground-state density n(r). Some connection is also made with an earlier result relating to the external potential by Levy and Perdew [Phys. Rev. A. 32, 2010 (1985)] and with the quite recent study of Joubert [J. Chem. Phys. 119, 1916 (2003)] relating to the separation of the exchange and correlation contributions.
Meta-GGA exchange-correlation functional with a balanced treatment of nonlocality
Constantin, L A; Della Sala, F
2013-01-01
We construct a meta-generalized-gradient approximation which properly balances the nonlocality contributions to the exchange and correlation at the semilocal level. This non-empirical functional shows good accuracy for a broad palette of properties (thermochemistry, structural properties) and systems (molecules, metal clusters, surfaces and bulk solids). The accuracy for several well known problems in electronic structure calculations, such as the bending potential of the silver trimer and the dimensional crossover of anionic gold clusters, is also demonstrated. The inclusion of empirical dispersion corrections is finally discussed and analyzed.
Lee, Ji-Hwan; Park, Jong-Hun; Soon, Aloysius
2016-07-01
Current materials-related calculations employ density-functional theory (DFT), commonly using the (semi-)local-density approximations for the exchange-correlation (xc) functional. The difficulties in arriving at a reasonable description of van der Waals (vdW) interactions by DFT-based models is to date a big challenge. In this work, we use various flavors of vdW-corrected DFT xc functionals—ranging from the quasiempirical force-field add-on vdW corrections to self-consistent nonlocal correlation functionals—to study the bulk lattice and mechanical properties (including the elastic constants and anisotropic indices) of the coinage metals (copper, silver, and gold). We critically assess the reliability of the different vdW-corrected DFT methods in describing their anisotropic mechanical properties which have been less reported in the literature. In the context of this work, we regard that our results reiterate the fact that advocating a so-called perfect vdW-inclusive xc functional for describing the general physics and chemistry of these coinage metals could be a little premature. These challenges to modern-day functionals for anisotropically strained coinage metals (e.g., at the faceted surfaces of nanostructures) may well be relevant to other strained material systems.
Choi, Jinwoo; Chang, EonHo; Anstine, Dylan M.; Madjet, Mohamed El-Amine; Chakraborty, Himadri S.
2017-02-01
We study the photoionization properties of the C60 versus C240 molecule in a spherical jellium frame of the density-functional method. Two prototypical approximations of the exchange-correlation (xc) functional are used: (i) the Gunnarsson-Lundqvist parametrization [Gunnarsson and Lundqvist, Phys. Rev. B 13, 4274 (1976), 10.1103/PhysRevB.13.4274] with a correction for the electron self-interaction (SIC) introduced artificially from the outset and (ii) a gradient-dependent augmentation of approximation (i) using the van Leeuwen and Baerends model potential [van Leeuwen and Baerends, Phys. Rev. A 49, 2421 (1994), 10.1103/PhysRevA.49.2421], in lieu of SIC, that restores electrons' asymptotic properties intrinsically within the formalism. Ground-state results from the two schemes for both molecules show differences in the shapes of mean-field potentials and bound-level properties. The choice of an xc scheme also significantly alters the dipole single-photoionization cross sections obtained by an ab initio method that incorporates linear-response dynamical correlations. Differences in the structures and ionization responses between C60 and C240 uncover the effect of molecular size on the underlying physics. Analysis indicates that the collective plasmon resonances with the gradient-based xc option produce results noticeably closer to the experimental data available for C60.
Choi, Jinwoo; Anstine, Dylan M; Madjet, Mohamed El-Amine; Chakraborty, Himadri S
2016-01-01
We study the photoionization properties of the C_60 versus C_240 molecule in a spherical jellium frame of density functional method. Two different approximations to the exchange-correlation (xc) functional are used: (i) The Gunnerson-Lundqvist parametrization [Phys. Rev. B 13, 4274 (1976)] with an explicit correction for the electron self-interaction (SIC) and (ii) a gradient-dependent augmentation of (i) by using the van Leeuwen and Baerends model potential [Phys. Rev. A 49, 2421 (1994)], in lieu of SIC, to implicitly restore electrons' asymptotic properties. Ground state results from the two schemes for both molecules show differences in the shapes of mean-field potentials and bound-level properties. The choice of a xc scheme also significantly alters the dipole single-photoionization cross sections obtained by an abinitio method that incorporates linear-response dynamical correlations. Differences in the structures and ionization responses between C_60 and C_240 uncover the effect of molecular size on the ...
Choi, Jinwoo; Chang, Eonho; Anstine, Dylan M.; Chakraborty, Himadri
2016-05-01
We study the ground state properties of C60 and C240 molecules in a spherical frame of local density approximation (LDA). Within this mean-field theory, two different approximations to the exchange-correlation (xc) functional are used: (i) The Gunnerson-Lundqvist parametrization augmented by a treatment to correct for the electron self-interaction and (ii) the van Leeuwen and Baerends (LB94) model potential that inclusively restores electron's asymptotic properties. Results show differences in the ground-state potential, level energies and electron densities between the two xc choices. We then use the ground structure to find the excited and ionized states of the systems and calculate dipole single-photoionization cross sections in a time-dependent LDA method that incorporates linear-response dynamical correlations. Comparative effects of the choices of xc on collective plasmon and single-excitation Auger resonances as well as on geometry driven cavity oscillations are found significant. The work is supported by the NSF, USA.
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.
Energy Technology Data Exchange (ETDEWEB)
Lee, Sang Uck [Univ. of Ulsan, Ulsan (Korea, Republic of)
2013-08-15
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.
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.
Smith, J. C.; Pribram-Jones, A.; Burke, K.
2016-06-01
Thermal density functional theory calculations often use the Mermin-Kohn-Sham scheme, but employ ground-state approximations to the exchange-correlation (XC) free energy. In the simplest solvable nontrivial model, an asymmetric Hubbard dimer, we calculate the exact many-body energies and the exact Mermin-Kohn-Sham functionals for this system and extract the exact XC free energy. For moderate temperatures and weak correlation, we find this approximation to be excellent. We extract various exact free-energy correlation components and the exact adiabatic connection formula.
Xu, Shengxian; Wang, Jinglan; Xia, Hongying; Zhao, Feng; Wang, Yibo
2015-02-01
The accurate prediction for the emission energies of the phosphorescent Ir (III) complexes is very useful for the realizing of full-color displays and large-area solid-state lighting in OLED fields. Quantum chemistry calculations based on TDDFT methods are most widely used to directly compute the triplet vertical excitation energies, yet sometimes the universality of these calculations can be limited because of the lack of experimental data for the relative family of structural analogues. In this letter, 16 literature emission energies at low temperature are linearly correlated with their theoretical values computed by TDDFT using exchange-correlation functionals containing various HF exchange percentage with the relation of E exp (em) = 1.2Ē calc (em). The relation is proven to be robust across a wide range of structures for Ir (III) complexes. These theoretical studies should be expected to provide some guides for the design and synthesis of efficient emitting materials.
Gould, Tim; Dobson, John F.
2013-01-01
By exploiting freedoms in the definitions of "correlation," "exchange," and "Hartree" physics in ensemble systems, we better generalise the notion of "exact exchange" (EXX) to systems with fractional occupations of the frontier orbitals, arising in the dissociation limit of some molecules. We introduce the linear EXX ("LEXX") theory whose pair distribution and energy are explicitly piecewise linear in the occupations f^{σ }i. We provide explicit expressions for these functions for frontier s and p shells. Used in an optimised effective potential (OEP) approach the LEXX yields energies bounded by the piecewise linear "ensemble EXX" (EEXX) energy and standard fractional optimised EXX energy: EEEXX ⩽ ELEXX ⩽ EEXX. Analysis of the LEXX explains the success of standard OEP methods for diatoms at large spacing, and why they can fail when both spins are allowed to be non-integer so that "ghost" Hartree interactions appear between opposite spin electrons in the usual formula. The energy ELEXX contains a cancellation term for the spin ghost case. It is evaluated for H, Li, and Na fractional ions with clear derivative discontinuities for all cases. The p-shell form reproduces accurate correlation-free energies of B-F and Al-Cl. We further test LEXX plus correlation energy calculations on fractional ions of C and F and again we find both derivative discontinuities and good agreement with exact results.
Gould, Tim; Dobson, John F
2013-01-07
By exploiting freedoms in the definitions of "correlation," "exchange," and "Hartree" physics in ensemble systems, we better generalise the notion of "exact exchange" (EXX) to systems with fractional occupations of the frontier orbitals, arising in the dissociation limit of some molecules. We introduce the linear EXX ("LEXX") theory whose pair distribution and energy are explicitly piecewise linear in the occupations f(i)(σ). We provide explicit expressions for these functions for frontier s and p shells. Used in an optimised effective potential (OEP) approach the LEXX yields energies bounded by the piecewise linear "ensemble EXX" (EEXX) energy and standard fractional optimised EXX energy: E(EEXX) ≤ E(LEXX) ≤ E(EXX). Analysis of the LEXX explains the success of standard OEP methods for diatoms at large spacing, and why they can fail when both spins are allowed to be non-integer so that "ghost" Hartree interactions appear between opposite spin electrons in the usual formula. The energy E(LEXX) contains a cancellation term for the spin ghost case. It is evaluated for H, Li, and Na fractional ions with clear derivative discontinuities for all cases. The p-shell form reproduces accurate correlation-free energies of B-F and Al-Cl. We further test LEXX plus correlation energy calculations on fractional ions of C and F and again we find both derivative discontinuities and good agreement with exact results.
Al-Hamdani, Yasmine S; von Lilienfeld, O Anatole; Michaelides, Angelos
2016-01-01
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. ...
Double-hybrid density-functional theory made rigorous
Sharkas, Kamal; Savin, Andreas
2010-01-01
We provide a rigorous derivation of a class of double-hybrid approximations, combining Hartree-Fock exchange and second-order Moller-Plesset correlation with a semilocal exchange-correlation density functional. These double-hybrid approximations contain only one empirical parameter and use a density-scaled correlation energy functional. Neglecting density scaling leads to an one-parameter version of the standard double-hybrid approximations. We assess the performance of these double-hybrid schemes on representative test sets of atomization energies and reaction barrier heights, and we compare to other hybrid approximations, including range-separated hybrids. Our best one-parameter double-hybrid approximation, called 1DH-BLYP, roughly reproduces the two parameters of the standard B2-PLYP or B2GP-PLYP double-hybrid approximations, which shows that these methods are not only empirically close to an optimum for general chemical applications but are also theoretically supported.
Kraisler, Eli; Kelson, Itzhak
2010-01-01
The total energies and the spin states for atoms and their first ions with Z = 1-86 are calculated within the the local spin-density approximation (LSDA) and the generalized-gradient approximation (GGA) to the exchange-correlation (xc) energy in density-functional theory. Atoms and ions for which the ground-state density is not pure-state v-representable, are treated as ensemble v- representable with fractional occupations of the Kohn-Sham system. A newly developed algorithm which searches over ensemble v-representable densities [E. Kraisler et al., Phys. Rev. A 80, 032115 (2009)] is employed in calculations. It is found that for many atoms the ionization energies obtained with the GGA are only modestly improved with respect to experimental data, as compared to the LSDA. However, even in those groups of atoms where the improvement is systematic, there remains a non-negligible difference with respect to the experiment. The ab-initio electronic configuration in the Kohn-Sham reference system does not always equ...
Labat, Frédéric; Baranek, Philippe; Domain, Christophe; Minot, Christian; Adamo, Carlo
2007-04-21
The two polymorphs of TiO2, rutile and anatase, have been investigated at the ab initio level using different Hamiltonians with all-electron Gaussian and projector augmented plane wave basis sets. Their equilibrium lattice parameters, relative stabilities, binding energies, and band structures have been evaluated. The calculations have been performed at the Hartree-Fock, density functional theory (DFT), and hybrid (B3LYP and PBE0) levels. As regards DFT, the local density and generalized gradient (PBE) approximations have been used. Our results show an excellent agreement with the experimental band structures and binding energies for the B3LYP and PBE0 functionals, while the best structural descriptions are obtained at the PBE0 level. However, no matter which Hamiltonian and method are used, anatase is found more stable than rutile, in contrast with recent experimental reports, although the relative stabilities of the two phases are very close to each other. Nevertheless, based on the overall results, the hybrid PBE0 functional appears as a good compromise to obtain an accurate description of both structural and electronic properties of solids.
Gritsenko, Oleg; Baerends, Evert Jan
2004-07-08
Time-dependent density functional theory (TDDFT) calculations of charge-transfer excitation energies omegaCT are significantly in error when the adiabatic local density approximation (ALDA) is employed for the exchange-correlation kernel fxc. We relate the error to the physical meaning of the orbital energy of the Kohn-Sham lowest unoccupied molecular orbital (LUMO). The LUMO orbital energy in Kohn-Sham DFT--in contrast to the Hartree-Fock model--approximates an excited electron, which is correct for excitations in compact molecules. In CT transitions the energy of the LUMO of the acceptor molecule should instead describe an added electron, i.e., approximate the electron affinity. To obtain a contribution that compensates for the difference, a specific divergence of fxc is required in rigorous TDDFT, and a suitable asymptotically correct form of the kernel fxc(asymp) is proposed. The importance of the asymptotic correction of fxc is demonstrated with the calculation of omegaCT(R) for the prototype diatomic system HeBe at various separations R(He-Be). The TDDFT-ALDA curve omegaCT(R) roughly resembles the benchmark ab initio curve omegaCT CISD(R) of a configuration interaction calculation with single and double excitations in the region R=1-1.5 A, where a sizable He-Be interaction exists, but exhibits the wrong behavior omegaCT(R)
Casida, Mark E.; Salahub, Dennis R.
2000-11-01
The time-dependent density functional theory (TD-DFT) calculation of excitation spectra places certain demands on the DFT exchange-correlation potential, vxc, that are not met by the functionals normally used in molecular calculations. In particular, for high-lying excitations, it is crucial that the asymptotic behavior of vxc be correct. In a previous paper, we introduced a novel asymptotic-correction approach which we used with the local density approximation (LDA) to yield an asymptotically corrected LDA (AC-LDA) potential [Casida, Casida, and Salahub, Int. J. Quantum Chem. 70, 933 (1998)]. The present paper details the theory underlying this asymptotic correction approach, which involves a constant shift to incorporate the effect of the derivative discontinuity (DD) in the bulk region of finite systems, and a spliced asymptotic correction in the large r region. This is done without introducing any adjustable parameters. We emphasize that correcting the asymptotic behavior of vxc is not by itself sufficient to improve the overall form of the potential unless the effect of the derivative discontinuity is taken into account. The approach could be used to correct vxc from any of the commonly used gradient-corrected functionals. It is here applied to the LDA, using the asymptotically correct potential of van Leeuwen and Baerends (LB94) in the large r region. The performance of our AC-LDA vxc is assessed for the calculation of TD-DFT excitation energies for a large number of excitations, including both valence and Rydberg states, for each of four small molecules: N2, CO, CH2O, and C2H4. The results show a significant improvement over those from either the LB94 or the LDA functionals. This confirms that the DD is indeed an important element in the design of functionals. The quality of TDLDA/LB94 and TDLDA/AC-LDA oscillator strengths were also assessed in what we believe to be the first rigorous assessment of TD-DFT molecular oscillator strengths in comparison with
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.
Energy Technology Data Exchange (ETDEWEB)
Arantes, J. T.; Lima, M. P.; Fazzio, A.; Xiang, H.; Wei, S. H.; Dalpian, G. M.
2009-04-01
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.
Göltl, Florian; Sautet, Philippe
2014-04-01
The inclusion of non-local interactions is one of the large challenges in density functional theory. Very promising methods are the vdW-DF2 and BEEF-vdW functionals, which combine a semi-local approximation for exchange interactions and a non-local correlation expression. In this work we apply those functionals to model the adsorption of short alkanes in the zeolite SSZ-13. Even though results for energetics are improved with respect to other vdW-DF based methods, we still find a comparatively large error compared to high-level calculations. These errors result from approximations in the determination of the dielectric function and of the van der Waals kernel. The insights presented in this work will help to understand the performance not only of vdW-DF2 and BEEF-vdW, but all vdW-DF based functionals in various chemically or physically important systems.
Local hybrid functionals: an assessment for thermochemical kinetics.
Kaupp, Martin; Bahmann, Hilke; Arbuznikov, Alexei V
2007-11-21
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(tau(W)(r)tau(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.
Morrison, Robert C
2015-01-07
Accurate densities were determined from configuration interaction wave functions for atoms and ions of Li, Be, and B with up to four electrons. Exchange-correlation potentials, Vxc(r), and functional derivatives of the noninteracting kinetic energy, δK[ρ]/δρ(r), obtained from these densities were used to examine their discontinuities as the number of electrons N increases across integer boundaries for N = 1, N = 2, and N = 3. These numerical results are consistent with conclusions that the discontinuities are characterized by a jump in the chemical potential while the shape of Vxc(r) varies continuously as an integer boundary is crossed. The discontinuity of the Vxc(r) is positive, depends on the ionization potential, electron affinity, and orbital energy differences, and the discontinuity in δK[ρ]/δρ(r) depends on the difference between the energies of the highest occupied and lowest unoccupied orbitals. The noninteracting kinetic energy and the exchange correlation energy have been computed for integer and noninteger values of N between 1 and 4.
Energy Technology Data Exchange (ETDEWEB)
Benam, M.R., E-mail: m_benam@pnu.ac.ir [Department of Physics, Payame Noor University, P.O. BOX 19395-3697 (Iran, Islamic Republic of); Abdoshahi, N.; Majidiyan Sarmazdeh, M. [Department of Physics, Payame Noor University, P.O. BOX 19395-3697 (Iran, Islamic Republic of)
2014-08-01
In this paper the effect of pressure on the structural and electronic properties of cubic-LaAlO{sub 3} including the equilibrium lattice constant, bulk modulus, derivative of bulk modulus and band structure have been calculated by density functional theory (DFT) using GGA, LDA, and PBEsol exchange correlation potentials. It is found that the change of the lattice constant with pressure has an exponential behavior: with increasing pressure, the lattice constant decreases first sharply at low pressures, and then more slowly at high pressures. Furthermore, the lattice constant calculated by the PBEsol method and the bulk modulus calculated by LDA and PBEsol methods are closer to the available experimental values than those obtained using other exchange correlation potentials. Regarding the electronic properties, it is shown that an increase in pressure increases the band gap, the change being 0.26 eV at 34.00 GPa. The total density of state (t-DOS) calculations demonstrate that increasing pressure has a significant effect on the core and conduction band, but little effect on the valence band. The band structure calculations indicate that, in this material, the band gap changes from indirect to direct at a pressure of about 25 GPa. Also, increasing pressure produces a clear curvature in the band structure near the bottom of the conduction band, a behavior consistent with the strong pressure dependence of the transport properties.
Benam, M. R.; Abdoshahi, N.; Majidiyan Sarmazdeh, M.
2014-08-01
In this paper the effect of pressure on the structural and electronic properties of cubic-LaAlO3 including the equilibrium lattice constant, bulk modulus, derivative of bulk modulus and band structure have been calculated by density functional theory (DFT) using GGA, LDA, and PBEsol exchange correlation potentials. It is found that the change of the lattice constant with pressure has an exponential behavior: with increasing pressure, the lattice constant decreases first sharply at low pressures, and then more slowly at high pressures. Furthermore, the lattice constant calculated by the PBEsol method and the bulk modulus calculated by LDA and PBEsol methods are closer to the available experimental values than those obtained using other exchange correlation potentials. Regarding the electronic properties, it is shown that an increase in pressure increases the band gap, the change being 0.26 eV at 34.00 GPa. The total density of state (t-DOS) calculations demonstrate that increasing pressure has a significant effect on the core and conduction band, but little effect on the valence band. The band structure calculations indicate that, in this material, the band gap changes from indirect to direct at a pressure of about 25 GPa. Also, increasing pressure produces a clear curvature in the band structure near the bottom of the conduction band, a behavior consistent with the strong pressure dependence of the transport properties.
Hybrid density functional theory LCAO calculations on phonons in Ba (Ti,Zr,Hf) O3
Evaestov, Robert A
2010-01-01
Phonon frequencies at {\\Gamma},X,M,R-points of Brilloin zone in cubic phase of Ba(Ti,Zr,Hf)O3 were first time calculated by frozen phonon method using density functional theory (DFT) with hybrid exchange correlation functional PBE0. The calculations use linear combination of atomic orbitals (LCAO) basis functions as implemented in CRYSTAL09 computer code. The Powell algorithm was applied for basis set optimization. In agreement with the experimental observations the structural instability via...
DEFF Research Database (Denmark)
Bast, Radovan; Jensen, Hans Jørgen Aagaard; Saue, Trond
2009-01-01
We report an implementation of adiabatic time-dependent density functional theory based on the 4-component relativistic Dirac-Coulomb Hamiltonian and a closed-shell reference. The implementation includes noncollinear spin magnetization and full derivatives of functionals, including hybrid...... and time reversal symmetry on trial vectors to obtain even better reductions in terms of memory and run time, and without invoking approximations. Further reductions are obtained by exploiting point group symmetries for D2h and subgroups in a symmetry scheme where symmetry reductions translate...... 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...
National Research Council Canada - National Science Library
Fahmi, Amir; Pietsch, Torsten; Mendoza, Cesar; Cheval, Nicolas
2009-01-01
.... This paper describes our group's achievements towards the development of multifunctional nanostructures via self-assembly of hybrid systems based on the block copolymer PS-b-P4VP and inorganic nanoparticles (NPs...
Gritsenko, Oleg V; Baerends, Evert Jan
2009-06-14
Time-dependent density functional (response) theory (TDDF(R)T) is applied almost exclusively in its adiabatic approximation (ATDDFT), which is restricted to predominantly single electronic excitations and neglects additional roots of the TDDFT eigenvalue problem stemming from the interaction between single and double excitations. We incorporate the effect of the latter interaction into a non-adiabatic frequency-dependent and spatially non-local Hartree-exchange-correlation (Hxc) kernel fCEDAHxc (r1, r2, omega), the explicit analytical expression of which is derived for interacting single and double excitations well separated from the other excitations, within the common energy denominator approximation (CEDA) for the Kohn-Sham (KS) and interacting density response functions, chis and chi, respectively. The kernel fCEDAHxc (r1, r2, omega) obtained from the direct analytical inverse of chiCEDAs and chiCEDA is a sum of the delta-function and non-local orbital-dependent spatial terms with frequency-dependent factors, with which fCEDAHxc acquires a modulated quadratic dependence on omega. The effective incorporation in fCEDAHxc of the complete manifold of excited states (through the delta function term) represents an extension of the kernel reported by Maitra, Zhang, Cave, and Burke [J. Chem. Phys., 2004, 120, 5932]. In the TDDFT eigenvalue equations considered in the diagonal approximation, fCEDAHxc generates two excitation energies omegaq and omegaq+1, which both correspond to the same single KS excitation omegasq, thus producing the effect of the single-double excitation interaction.
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.)
Improved Lieb-Oxford exchange-correlation inequality with gradient correction
Mathieu, Lewin
2014-01-01
We prove a Lieb-Oxford-type inequality on the exchange-correlation energy of a general many-particle quantum state, with a lower constant than the original statement but involving an additional gradient correction. The result is similar to a recent inequality of Benguria, Bley and Loss, except that the correction term is purely local, as is appropriate for density functional theory.
Vyboishchikov, Sergei F
2016-12-05
We report correlation energies, electron densities, and exchange-correlation potentials obtained from configuration interaction and density functional calculations on spherically confined He, Be, Be(2+) , and Ne atoms. The variation of the correlation energy with the confinement radius Rc is relatively small for the He, Be(2+) , and Ne systems. Curiously, the Lee-Yang-Parr (LYP) functional works well for weak confinements but fails completely for small Rc . However, in the neutral beryllium atom the CI correlation energy increases markedly with decreasing Rc . This effect is less pronounced at the density-functional theory level. The LYP functional performs very well for the unconfined Be atom, but fails badly for small Rc . The standard exchange-correlation potentials exhibit significant deviation from the "exact" potential obtained by inversion of Kohn-Sham equation. The LYP correlation potential behaves erratically at strong confinements. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.
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.
A multiconfigurational hybrid density-functional theory
Sharkas, Kamal; Jensen, Hans Jørgen Aa; Toulouse, Julien; 10.1063/1.4733672
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 of the usual hybrid approximations by essentially adding a fraction \\lambda of exact static correlation in addition to the fraction \\lambda of exact exchange. Test calculations on the cycloaddition reactions of ozone with ethylene or acetylene and the dissociation of diatomic molecules with the Perdew-Burke-Ernzerhof (PBE) and Becke-Lee-Yang-Parr (BLYP) density functionals show that a good value of \\lambda is 0.25, as in the usual hybrid approximations. The results suggest that the proposed multiconfigurational hybrid approximations can improve over usual density-functional calculations for situations with strong static correlation effects.
Kweon, Kyoung E.; Hwang, Gyeong S.
2012-10-01
The structure and property prediction of metal oxides can significantly be improved by incorporating exact Hartree-Fock (HF) exchange into density functional theory (DFT), which is the so-called hybrid DFT. We explored the impact of HF exchange inclusion on the predicted structural, bonding, and electronic properties of bismuth vanadate (BiVO4), with particular attention to the difference between its monoclinic and tetragonal scheelite phases. The applied exchange-correlation (xc) functionals include the gradient corrected Perdew-Burke-Ernzerhof (PBE) and the PBE-HF hybrid functionals with HF exchange amounts of 10%, 25%, and 50%. We find that the PBE-HF25% yields a monoclinic structure in very close agreement with the experimentally determined structure, while the PBE-HF50% tends to overestimate the monoclinic distortion and the PBE/PBE-HF10% can hardly identify a distinct monoclinic configuration at ambient conditions. Electronic structure analysis reveals that the increasing monoclinic distortion with the amount of HF exchange is related to the enhancement of hybridization between Bi 6s-O 2p antibonding states and unoccupied Bi 6p states. The bonding mechanisms and band structures of the monoclinic and tetragonal phases of BiVO4 were also investigated, and we discuss how the predictions are sensitive to the xc functional choice.
Electroactive functional hybrid layered nanocomposites
Energy Technology Data Exchange (ETDEWEB)
Destri, Giovanni Li; Torrisi, Vanna; Marletta, Giovanni [Laboratory for Molecular Surfaces and Nanotechnology (LAMSUN) - University of Catania and CSGI - Catania (Italy)
2012-07-11
Two methodologies to build new nanostructured hybrid layered nanocomposites are presented. The first one involves the preparation of hybrid metal/polymer nanolayers (NLs) by combining two monolayer preparation techniques: Horizontal Precipitation Langmuir Blodgett method (HP-ML), for copolymer monolayers and sputter deposition technique, for Au NLs deposition. The second methodology is aimed to prepare regular arrays of nanopores, with diameter ranging between 40-100 nm, in ultra-thin films of electroactive polymers, to obtain embedded regular arrays of nanopores filled by a further electroactive organic component. The produced hybrid MLs have been characterized by means of X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and Grazing Incidence X-ray Diffraction (GI-XRD). In the first case, current-voltage (I-V) measurements demonstrate that the multilayers exhibit a bipolar conduction behaviour (electrons and holes carriers), with a peculiar transition in the nature of the majority carriers (from holes to electrons) above a threshold number of bilayers. In the second case, it is found that the degree of pore filling, as well as the polymer crystallinity can be easily modulated, prompting the tuning of the photoresponse of the nanocomposites.
Rodríguez, Juan I; Thompson, David C; Ayers, Paul W; Köster, Andreas M
2008-06-14
A new numerical integration procedure for exchange-correlation energies and potentials is proposed and "proof of principle" results are presented. The numerical integration grids are built from sparse-tensor product grids (constructed according to Smolyak's prescription [Dokl. Akad. Nauk. 4, 240 (1963)] ) on the unit cube. The grid on the unit cube is then transformed to a grid over real space with respect to a weight function, which we choose to be the promolecular density. This produces a "whole molecule" grid, in contrast to conventional integration methods in density-functional theory, which use atom-in-molecule grids. The integration scheme was implemented in a modified version of the DEMON2K density-functional theory program, where it is used to evaluate integrals of the exchange-correlation energy density and the exchange-correlation potential. Ground-state energies and molecular geometries are accurately computed. The biggest advantages of the grid are its flexibility (it is easy to change the number and distribution of grid points) and its whole molecule nature. The latter feature is potentially helpful for basis-set-free computational algorithms.
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 ...
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 ...
SCAN-based hybrid and double-hybrid density functionals from models without fitted parameters
Hui, Kerwin; Chai, Jeng-Da
2015-01-01
By incorporating the nonempirical SCAN semilocal density functional [Sun, Ruzsinszky, and Perdew, Phys. Rev. Lett. 115, 036402 (2015)] in the underlying expression of four existing hybrid and double-hybrid models, we propose one hybrid (SCAN0) and three double-hybrid (SCAN0-DH, SCAN-QIDH, and SCAN0-2) density functionals, which are free from any fitted parameters. The SCAN-based double-hybrid functionals consistently outperform their parent SCAN semilocal functional for self-interaction probl...
Neese, Frank; Schwabe, Tobias; Grimme, Stefan
2007-03-28
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 approximately 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.
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....
Swart, M; Snijders, JG
The geometries of a set of small molecules were optimized using eight different exchange-correlation (xc) potentials in a few different basis sets of Slater-type orbitals, ranging from a minimal basis (I) to a triple-zeta valence basis plus double polarization functions (VII). This enables a
Accurate exchange-correlation energies for the warm dense electron gas
Malone, FD; Blunt, NS; Brown, EW; Lee, DKK; Spencer, JS; Foulkes, WMC; Shepherd, JJ
2016-01-01
Density matrix quantum Monte Carlo (DMQMC) is used to sample exact-on-average $N$-body density matrices for uniform electron gas systems of up to 10$^{124}$ matrix elements via a stochastic solution of the Bloch equation. The results of these calculations resolve a current debate over the accuracy of the data used to parametrize finite-temperature density functionals. Exchange-correlation energies calculated using the real-space restricted path-integral formalism and the $k$-space configurati...
SCAN-based hybrid and double-hybrid density functionals from parameter-free models
Hui, Kerwin
2015-01-01
By incorporating the nonempirical SCAN semilocal density functional [Sun, Ruzsinszky, and Perdew, Phys. Rev. Lett. 115, 036402 (2015)] in the underlying expression, we propose one hybrid (SCAN0) and three double-hybrid (SCAN0-DH, SCAN-QIDH, and SCAN0-2) density functionals, which are free of any empirical parameter. The SCAN-based hybrid and double-hybrid functionals consistently outperform their parent SCAN semilocal functional for a wide range of applications. The SCAN-based semilocal, hybrid, and double-hybrid functionals generally perform better than the corresponding PBE-based functionals. In addition, the SCAN0-2 and SCAN-QIDH double-hybrid functionals significantly reduce the qualitative failures of the SCAN semilocal functional, such as the self-interaction error and noncovalent interaction error, extending the applicability of the SCAN-based functionals to a very diverse range of systems.
Smiga, Szymon; Mussard, Bastien; Buksztel, Adam; Grabowski, Ireneusz; Luppi, Eleonora; Toulouse, Julien
2016-01-01
We introduce an orbital-optimized double-hybrid (DH) scheme using the optimized-effective-potential (OEP) method. The orbitals are optimized using a local potential corresponding to the complete exchange-correlation energy expression including the second-order M{{\\o}}ller-Plesset (MP2) correlation contribution. We have implemented a one-parameter version of this OEP-based self-consistent DH scheme using the BLYP density-functional approximation and compared it to the corresponding non-self-consistent DH scheme for calculations on a few closed-shell atoms and molecules. While the OEP-based self-consistency does not provide any improvement for the calculations of ground-state total energies and ionization potentials, it does improve the accuracy of electron affinities and restores the meaning of the LUMO orbital energy as being connected to a neutral excitation energy. Moreover, the OEP-based self-consistent DH scheme provides reasonably accurate exchange-correlation potentials and correlated densities.
Göltl, Florian; Hafner, Jürgen
2012-02-14
The influence of the exchange-correlation functional (semilocal gradient corrected or hybrid functional) on density-functional studies of the adsorption of CO and NO in Cu- and Co-exchanged chabazite has been investigated, extending the studies of the structural and electronic properties of these materials [F. Göltl and J. Hafner, J. Chem. Phys. 136, 064501 (2012); 136, 064502 (2012)] and including for comparison carbonyls and nitrosyls of Cu and Co. Hybrid functionals predict much lower adsorption energies than conventional semilocal functionals, in better agreement with experiment as far as data are available for comparison. The calculated adsorption energies show a strong linear correlation with the stability of the cation sites. For Cu(I)-chabazite the calculated adsorption energies span almost the interval between the adsorption energies calculated for pure neutral and positively charged Cu-carbonyls and nitrosyls. For divalent Cu(II) and Co(II) the adsorption energies at cations in chabazite are much lower than the metal-molecule binding energies in the free carbonyls or nitrosyls, especially for the most stable cation location in a six-membered ring of the chabazite structure. For the stretching modes of adsorbed CO only hybrid functionals reproduce the blueshift of the frequency reported for all Cu(I)- and Co(II)-zeolites. For Cu(II)-chabazite both types of functionals predict a blueshift, the larger value calculated with hybrid functionals being in better agreement with observation. For NO adsorbed on Cu(I)-chabazite all functionals produce a redshift, the smaller value derived with hybrid functionals being in better agreement with experiment. For NO adsorbed in Cu(II)- and Co(II)-chabazite gradient-corrected functionals produce the best agreement with experiment for cations located in a six-membered ring. Semilocal functionals tend to underestimate the frequencies, while hybrid functionals tend to overestimate. The decisive factors determining the
Hybrid functional study of α-uranium
Kaur, Gurpreet; Chinnappan, Ravi; Panigrahi, B. K.
2016-05-01
We have used the hybrid density functionals to study the structural and electronic properties of alpha-U. The fraction of exact Hartree Folk exchange used is varied from 0.0 to 0.6. The equilibrium volume is found to be underestimated and bulk modulus overestimated with HSE as compared to both calculated by PBE and the experimental values. Electronic bands below the Fermi level are found to shift to lower energy with respect to PBE electronic bands which itself gives the bands shifted to lower energies as compared to UPS experiments.
Hybrid distortion function for JPEG steganography
Wang, Zichi; Zhang, Xinpeng; Yin, Zhaoxia
2016-09-01
A hybrid distortion function for JPEG steganography exploiting block fluctuation and quantization steps is proposed. To resist multidomain steganalysis, both spatial domain and discrete cosine transformation (DCT) domain are involved in the proposed distortion function. In spatial domain, a distortion value is allotted for each 8×8 block according to block fluctuation. In DCT domain, quantization steps are employed to allot distortion values for DCT coefficients in a block. The two elements, block distortion and quantization steps, are combined together to measure the embedding risk. By employing the syndrome trellis coding to embed secret data, the embedding changes are constrained in complex regions, where modifications are hard to be detected. When compared to current state-of-the-art steganographic methods for JPEG images, the proposed method presents less detectable artifacts.
Disruption of mitochondrial function in interpopulation hybrids of Tigriopus californicus.
Ellison, Christopher K; Burton, Ronald S
2006-07-01
Electron transport system (ETS) function in mitochondria is essential for the aerobic production of energy. Because ETS function requires extensive interactions between mitochondrial and nuclear gene products, coadaptation between mitochondrial and nuclear genomes may evolve within populations. Hybridization between allopatric populations may then expose functional incompatibilities between genomes that have not coevolved. The intertidal copepod Tigriopus californicus has high levels of nucleotide divergence among populations at mitochondrial loci and suffers F2 hybrid breakdown in interpopulation hybrids. We hypothesize that hybridization results in incompatibilities among subunits in ETS enzyme complexes and that these incompatibilities result in diminished mitochondrial function and fitness. To test this hypothesis, we measured fitness, mitochondrial function, and ETS enzyme activity in inbred recombinant hybrid lines of Tigriopus californicus. We found that (1) both fitness and mitochondrial function are reduced in hybrid lines, (2) only those ETS enzymes with both nuclear and mitochondrial subunits show a loss of activity in hybrid lines, and (3) positive relationships exist between ETS enzyme activity and mitochondrial function and between mitochondrial function and fitness. We also present evidence that hybrid lines harboring mitochondrial DNA (mtDNA) and mitochondrial RNA polymerase (mtRPOL) from the same parental source population have higher fitness than those with mtDNA and mtRPOL from different populations, suggesting that mitochondrial gene regulation may play a role in disruption of mitochondrial performance and fitness of hybrids. These results suggest that disruption of coadaptation between nuclear and mitochondrial genes contributes to the phenomenon of hybrid breakdown.
Schmidt, Tobias; Makmal, Adi; Kronik, Leeor; Kümmel, Stephan
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 potent...
Band Anticrossing in Dilute Germanium Carbides Using Hybrid Density Functionals
Stephenson, Chad A.; O'brien, William A.; Qi, Meng; Penninger, Michael; Schneider, William F.; Wistey, Mark A.
2016-04-01
Dilute germanium carbides (Ge1- x C x ) offer a direct bandgap for compact silicon photonics, but widely varying properties have been reported. This work reports improved band structure calculations for Ge1- x C x using ab initio simulations that employ the HSE06 exchange-correlation density functional. Contrary to Vegard's law, the conduction band minimum at Γ is consistently found to decrease with increasing C content, while L and X valleys change much more slowly. The calculated Ge bandgap is within 11% of experimental values. A decrease in energy at the Γ conduction band valley of (170 meV ± 50)/%C is predicted, leading to a direct bandgap for x > 0.008. These results indicate a promising material for Group IV lasers.
Energy Technology Data Exchange (ETDEWEB)
Ahuja, B.L., E-mail: blahuja@yahoo.ik [Department of Physics, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India); Raykar, Veera; Joshi, Ritu [Department of Physics, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India); Tiwari, Shailja [Department of Physics, Govt. Women Engineering College, Ajmer 305001, Rajasthan (India); Talreja, Sonal [Department of Computer Science, M.L. Sukhadia University, Udaipur 313001 (India); Choudhary, Gopal [Department of Physics, Techno India NJR Institute of Technology, Udaipur 313001, Rajasthan (India)
2015-05-15
We report Compton profiles of SnS and SnTe at a momentum resolution of 0.34 a.u. using a 20 Ci {sup 137}Cs Compton spectrometer. To compare our experimental data, we have also computed the theoretical Compton profiles using density functional theory within linear combination of atomic orbitals (LCAO) method. To interpret the relative nature of bonding in these compounds, we have scaled the experimental and theoretical Compton profiles on equal-valence-electron-density (EVED). On the basis of EVED profiles, it is seen that SnTe shows more covalent character than SnS. To rectify the substantial disagreement between experimental and theoretical band gaps, we have also presented the energy bands and density of states of both the compounds using full-potential linearized augmented plane wave method (FP-LAPW) including spin–orbit interaction within the PBEsol exchange-correlation potential.
Clay, Raymond; Morales, Miguel; Bonev, Stanimir
Lithium at ambient conditions is the simplest alkali metal and exhibits textbook nearly-free electron character. However, increased core/valence electron overlap under compression leads to surprisingly complex behavior. Dense lithium is known to posses a maximum in the melting line, a metal to semiconductor phase transition around 80GPa, reemergent metallicity around 120GPa, and low coordination solid and liquid phases. In addition to its complex electronic structure at high pressure, the atomic mass of lithium is low enough that nuclear quantum effects could have a nontrivial impact on its phase diagram. Through a combination of density functional theory based path-integral and classical molecular dynamics simulations, we have investigated the impact of both nuclear quantum effects and anharmonicity on the melting line and solid phase boundaries. Additionally, we have determined the robustness of previously predicted tetrahedral clustering in the dense liquid to the inclusion of nuclear quantum effects and approximate treatment of electronic exchange-correlation effects.
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.
Nemykin, Victor N; Hadt, Ryan G
2006-10-01
Influence of molecular geometry, type of exchange-correlation functional, and contraction scheme of basis set applied at the iron nuclei have been tested in the calculation of 57Fe Mössbauer isomer shifts and quadrupole splittings for a wide range of ligand types, as well as oxidation and spin states, in inorganic and organometallic systems. It has been found that uncontraction of the s-part of Wachter's full-electron basis set at the iron nuclei does not appreciably improve the calculated isomer shifts. The observed correlations for all tested sets of geometries are close to each other and predominantly depend on the employed exchange-correlation functional with B3LYP functional being slightly better as compared to BPW91. Both hybrid (B3LYP) and pure (BPW91) exchange-correlation functionals are suitable for the calculation of isomer shifts in organometallic compounds. Surprisingly, it has been found that the hybrid B3LYP exchange-correlation functional completely fails in accurate prediction of quadrupole splittings in ferrocenes, while performance of the pure BPW91 functional for the same systems was excellent. This observation has been explained on the basis of relationship between the amount of Hartree-Fock exchange involved in the applied exchange-correlation functional and the calculated HOMO-LUMO energy gap in ferrocenes. On the basis of this explanation, use of only pure exchange-correlation functionals has been suggested for accurate prediction of Mössbauer spectra parameters in ferrocenes.
DFT studies of CNT-functionalized uracil-acetate hybrids
Mirzaei, Mahmoud; Gulseren, Oguz
2015-09-01
Calculations based on density functional theory (DFT) have been performed to investigate the stabilities and properties of hybrid structures consisting of a molecular carbon nanotube (CNT) and uracil acetate (UA) counterparts. The investigated models have been relaxed to minimum energy structures and then various physical properties and nuclear magnetic resonance (NMR) properties have been evaluated. The results indicated the effects of functionalized CNT on the properties of hybrids through comparing the results of hybrids and individual structures. The oxygen atoms of uracil counterparts have been seen as the detection points of properties for the CNT-UA hybrids.
Importance of finite-temperature exchange correlation for warm dense matter calculations
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), 10.1103/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.
Construction of Exchange-Correlation Potentials for Strongly Interacting One-Dimensional Systems
Silva, J. Wildon O.; Vieira, Daniel
2017-08-01
One-dimensional (1D) systems are useful laboratories aiming further improvement of electronic structure calculations. In order to simulate electron-electron interactions, two types of expressions are commonly considered: soft-Coulomb and exponential. For both cases, in the context of density-functional theory (DFT), 1D systems can be employed to gain insight into the ingredients accurate exchange-correlation (XC) density functionals must incorporate. A question of major interest is the treatment of strongly interacting situations, one of the main modern challenges for DFT. In this manuscript, we propose a generalization of preexisting XC potentials which can be applied to investigate the transition from weak to strong interactions. Specifically, we employ the intriguing behavior of electrons confined in one dimension: the spin-charge separation, for which spin and charge are decoupled to form two independent quasiparticles, spinons, and chargons. By means of Friedel oscillations, our results indicate it is possible to reproduce the weak-strong interaction transition by using a simple strategy we name, from previous works, spin-charge separation correction (SCSC). In addition, SCSC also yields good results in reproducing the constancy of the highest occupied Kohn-Sham eigenvalues upon fractional electron charges.
Sato, Shunsuke A.; Taniguchi, Yasutaka; Shinohara, Yasushi; Yabana, Kazuhiro
2015-12-01
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.
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.
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...
Generalization of Dielectric-Dependent Hybrid Functionals to Finite Systems
Brawand, Nicholas P.; Vörös, Márton; Govoni, Marco; Galli, Giulia
2016-10-01
The accurate prediction of electronic and optical properties of molecules and solids is a persistent challenge for methods based on density functional theory. We propose a generalization of dielectric-dependent hybrid functionals to finite systems where the definition of the mixing fraction of exact and semilocal exchange is physically motivated, nonempirical, and system dependent. The proposed functional yields ionization potentials, and fundamental and optical gaps of many, diverse molecular systems in excellent agreement with experiments, including organic and inorganic molecules and semiconducting nanocrystals. We further demonstrate that this hybrid functional gives the correct alignment between energy levels of the exemplary TTF-TCNQ donor-acceptor system.
Accurate Exchange-Correlation Energies for the Warm Dense Electron Gas.
Malone, Fionn D; Blunt, N S; Brown, Ethan W; Lee, D K K; Spencer, J S; Foulkes, W M C; Shepherd, James J
2016-09-09
The density matrix quantum Monte Carlo (DMQMC) method is used to sample exact-on-average N-body density matrices for uniform electron gas systems of up to 10^{124} matrix elements via a stochastic solution of the Bloch equation. The results of these calculations resolve a current debate over the accuracy of the data used to parametrize finite-temperature density functionals. Exchange-correlation energies calculated using the real-space restricted path-integral formalism and the k-space configuration path-integral formalism disagree by up to ∼10% at certain reduced temperatures T/T_{F}≤0.5 and densities r_{s}≤1. Our calculations confirm the accuracy of the configuration path-integral Monte Carlo results available at high density and bridge the gap to lower densities, providing trustworthy data in the regime typical of planetary interiors and solids subject to laser irradiation. We demonstrate that the DMQMC method can calculate free energies directly and present exact free energies for T/T_{F}≥1 and r_{s}≤2.
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.
Preparation and characterization of functional silica hybrid magnetic nanoparticles
Digigow, Reinaldo G.; Dechézelles, Jean-François; Dietsch, Hervé; Geissbühler, Isabelle; Vanhecke, Dimitri; Geers, Christoph; Hirt, Ann M.; Rothen-Rutishauser, Barbara; Petri-Fink, Alke
2014-08-01
We report on the synthesis and characterization of functional silica hybrid magnetic nanoparticles (SHMNPs). The co-condensation of 3-aminopropyltriethoxysilane (APTES) and tetraethyl orthosilicate (TEOS) in presence of superparamagnetic iron oxide nanoparticles (SPIONs) leads to hybrid magnetic silica particles that are surface-functionalized with primary amino groups. In this work, a comprehensive synthetic study is carried out and completed by a detailed characterization of hybrid particles' size and morphology, surface properties, and magnetic responses using different techniques. Depending on the mass ratio of SPIONs and the two silanes (TEOS and APTES), we were able to adjust the number of surface amino groups and tune the magnetic properties of the superparamagnetic hybrid particles.
Hybride magnetic nanostructure based on amino acids functionalized polypyrrole
Nan, Alexandrina; Bunge, Alexander; Turcu, Rodica
2015-12-01
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.
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.
Application of Hybrid Functions for Solving Duffing-Harmonic Oscillator
Directory of Open Access Journals (Sweden)
Mohammad Heydari
2014-01-01
Full Text Available A numerical method for finding the solution of Duffing-harmonic oscillator is proposed. The approach is based on hybrid functions approximation. The properties of hybrid functions that consist of block-pulse and Chebyshev cardinal functions are discussed. The associated operational matrices of integration and product are then utilized to reduce the solution of a strongly nonlinear oscillator to the solution of a system of algebraic equations. The method is easy to implement and computationally very attractive. The results are compared with the exact solution and results from several recently published methods, and the comparisons showed proper accuracy of this method.
Spin projection with double hybrid density functional theory.
Thompson, Lee M; Hratchian, Hrant P
2014-07-21
A spin projected double-hybrid density functional theory is presented that accounts for different scaling of opposite and same spin terms in the second order correction. This method is applied to three dissociation reactions which in the unprojected formalism exhibit significant spin contamination with higher spin states. This gives rise to a distorted potential surface and can lead to poor geometries and energies. The projected method presented is shown to improve the description of the potential over unprojected double hybrid density functional theory. Comparison is made with the reference states of the two double hybrid functionals considered here (B2PLYP and mPW2PLYP) in which the projected potential surface is degraded by an imbalance in the description of dynamic and static correlation.
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...
Density-based mixing parameter for hybrid functionals
Marques, Miguel A. L.; Vidal, Julien; Oliveira, Micael J. T.; Reining, Lucia; Botti, Silvana
2011-01-01
A very popular ab initio scheme to calculate electronic properties in solids is the use of hybrid functionals in density functional theory (DFT) that mixes a portion of the Fock exchange with DFT functionals. In spite of its success, a major problem still remains, related to the use of one single mixing parameter for all materials. Guided by physical arguments that connect the mixing parameter to the dielectric properties of the solid, and ultimately to its band gap, we propose a method to calculate this parameter from the electronic density alone. This approach is able to cut significantly the error of traditional hybrid functionals for large and small gap materials, while retaining a good description of the structural properties. Moreover, its implementation is simple and leads to a negligible increase of the computational time.
Hybrid bounds for Dirichlet's L-function
Huxley, M. N.; Watt, N.
2000-11-01
This is a paper about upper bounds for Dirichlet's L-function, L(s, [chi]), on its critical line (s + s¯ = 1). It is to be assumed throughout that, unless otherwise stated, the Dirichlet character, [chi], is periodic modulo a prime, r, and is not the principal character mod r. Our main theorem below shows that, if [epsilon] > 0, thenformula here(where A is an absolute constant), for 0 < [alpha] = (log r)/(log t) [less-than-or-eq, slant] 2/753 [minus sign] [epsilon]. Somewhat weaker bounds are obtained for other cases where 0 < [alpha] [less-than-or-eq, slant] 11/180 [minus sign] [epsilon]. Note that in [13] it was shown that, for 0 < [alpha] [less-than-or-eq, slant] 2/57,formula hereOur main theorem is a corollary of the new bounds we prove for certain exponential sums, S, with a Dirichlet character factor:formula herewhere M2 [less-than-or-eq, slant] 2M and f(x) is a real function whose derivatives satisfy certain conditions restricting their size.
Application and future challenges of functional nanocarbon hybrids.
Shearer, Cameron J; Cherevan, Alexey; Eder, Dominik
2014-04-16
Hybridizing nanocarbons, such as carbon nanotubes (CNTs) or graphene, with an active material is a powerful strategy towards designing next-generation functional materials for environmental and sustainable energy applications. While research on nanocomposites, created by dispersing the nanocarbon into polymer or ceramic matrices, began almost immediately after the popularization of CNTs and graphene in 1991 and 2004, respectively, nanocarbon hybrids are a relatively recent addition to the family of composite materials. In contrast to nanocomposites, which typically combine the intrinsic properties of both compounds, nanocarbon hybrids additionally provide access to both a large surface area required for gas/liquid-solid interactions and an extended interface, through which charge and energy transfer processes create synergistic effects that result in unique properties and superior performance. This progress report looks at the history of research on nanocarbons (fullerenes, CNTs and graphene) and their composites and hybrids, presents the origin of synergistic effects, reviews the most intriguing results on nanocarbon hybrid performance in heterogeneous catalysis, electrocatalysis, photocatalysis, batteries, supercapacitors, photovoltaics and sensors, and discusses remaining challenges and future research directions.
Ab initio molecular dynamics using hybrid density functionals
Guidon, Manuel; Schiffmann, Florian; Hutter, Jürg; Vandevondele, Joost
2008-06-01
Ab initio molecular dynamics simulations with hybrid density functionals have so far found little application due to their computational cost. In this work, an implementation of the Hartree-Fock exchange is presented that is specifically targeted at ab initio molecular dynamics simulations of medium sized systems. We demonstrate that our implementation, which is available as part of the CP2K/Quickstep program, is robust and efficient. Several prescreening techniques lead to a linear scaling cost for integral evaluation and storage. Integral compression techniques allow for in-core calculations on systems containing several thousand basis functions. The massively parallel implementation respects integral symmetry and scales up to hundreds of CPUs using a dynamic load balancing scheme. A time-reversible multiple time step scheme, exploiting the difference in computational efficiency between hybrid and local functionals, brings further time savings. With extensive simulations of liquid water, we demonstrate the ability to perform, for several tens of picoseconds, ab initio molecular dynamics based on hybrid functionals of systems in the condensed phase containing a few thousand Gaussian basis functions.
Schipper, P. R. T.; Gritsenko, O. V.; van Gisbergen, S. J. A.; Baerends, E. J.
2000-01-01
An approximate Kohn-Sham exchange-correlation potential νxcSAOP is developed with the method of statistical averaging of (model) orbital potentials (SAOP) and is applied to the calculation of excitation energies as well as of static and frequency-dependent multipole polarizabilities and hyperpolarizabilities within time-dependent density functional theory (TDDFT). νxcSAOP provides high quality results for all calculated response properties and a substantial improvement upon the local density approximation (LDA) and the van Leeuwen-Baerends (LB) potentials for the prototype molecules CO, N2, CH2O, and C2H4. For the first three molecules and the lower excitations of the C2H4 the average error of the vertical excitation energies calculated with νxcSAOP approaches the benchmark accuracy of 0.1 eV for the electronic spectra.
Origin of the step structure of molecular exchange-correlation potentials.
Kohut, Sviataslau V; Polgar, Alexander M; Staroverov, Viktor N
2016-08-21
The exact exchange-correlation potential of a stretched heteronuclear diatomic molecule exhibits a localized upshift in the region around the more electronegative atom; by this device the Kohn-Sham scheme ensures that the molecule dissociates into neutral atoms. Baerends and co-workers showed earlier that the upshift originates in the response part of the exchange-correlation potential. We describe a reliable numerical method for constructing the response potential of a given many-electron system and report accurate plots of this quantity. We also demonstrate that the step feature itself can be obtained directly from the interacting wavefunction of the system by computing the so-called average local electron energy. These findings illustrate in previously unavailable detail the mechanism of the formation of the upshift and the role played by static correlation in this process.
Molecular Kohn-Sham exchange-correlation potential from the correlated ab initio electron density
Gritsenko, Oleg V.; van Leeuwen, Robert; Baerends, Evert Jan
1995-09-01
The molecular Kohn-Sham (KS) exchange-correlation potential vxc has been constructed for LiH from the correlated ab initio density ρ by means of the simple iterative procedure developed by van Leeuwen and Baerends [Phys. Rev. A 49, 2421 (1994)]. The corresponding KS energy characteristics, such as the kinetic energy of noninteracting particles Ts, kinetic part of the exchange-correlation energy Tc, and energy of the highest occupied molecular orbital ɛN, have been obtained with reasonable accuracy. A relation between the form of vxc and the electronic structure of LiH has been discussed. Test calculations for the two-electron H2 molecule have shown the efficiency of the procedure.
Exchange-correlation energy of a hole gas including valence band coupling
Bobbert, P. A.; Wieldraaijer, H.; van der Weide, R.; Kemerink, M.; Koenraad, P. M.; Wolter, J. H.
1997-08-01
We have calculated an accurate exchange-correlation energy of a hole gas, including the complexities related to the valence band coupling as occurring in semiconductors like GaAs, but excluding the band warping. A parametrization for the dependence on the density and the ratio between light- and heavy-hole masses is given. We apply our results to a hole gas in an AlxGa1-xAs/GaAs/AlxGa1-xAs quantum well and calculate the two-dimensional band structure and the band-gap renormalization. The inclusion of the valence band coupling in the calculation of the exchange-correlation potentials for holes and electrons leads to a much better agreement between theoretical and experimental data than when it is omitted.
Hybrid functional studies of defects and hole polarons in oxides
Varley, Joel
Transparent conducting oxides (TCOs) are ubiquitous, appearing in windows, flat-panel displays, solar cells, solid-state lighting, and transistors that all exploit TCOs' combination of high electrical conductivity and optical transparency. Thanks to this large and growing list of applications, there has been a surge of interest in the science of these materials, focusing on the fundamental properties and doping opportunities in traditional TCOs as well as the exploration of promising new candidate materials. Hybrid density functional theory has proven instrumental in elucidating the physics of TCOs. One example is the study of dopants and defects that determine the conductivity. Accurate formation energies and charge-state transition levels can now be obtained thanks to the accurate electronic structure provided by a hybrid functional. This allows us to address the origins of unintentional conductivity: for SnO2, In2O3, and Ga2O3, we demonstrate that this is not due to native defects such as oxygen vacancies, but must be attributed to unintentional incorporation of impurities. We can also provide guidelines for achieving higher doping levels, suggesting several impurities as candidate donors with high solubility. Limitations on doping due to the formation or incorporation of compensating centers are addressed as well. Hybrid functional calculations also overcome the shortcomings associated with traditional local or semi-local functionals, which do not properly describe charge localization. Hybrid functionals accurately describe polaron formation, i.e., the self-trapping of holes when p - type doping of the oxide materials is attempted. Consequences of polaron formation for optical characterization of the material will be discussed. This work was performed in collaboration with Anderson Janotti and Chris G. Van de Walle, and was in part under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
From molecular chemistry to hybrid nanomaterials. Design and functionalization.
Mehdi, Ahmad; Reye, Catherine; Corriu, Robert
2011-02-01
This tutorial review reports upon the organisation and functionalization of two families of hybrid organic-inorganic materials. We attempted to show in both cases the best ways permitting the organisation of materials in terms of properties at the nanometric scale. The first family concerns mesoporous hybrid organic-inorganic materials prepared in the presence of a structure-directing agent. We describe the functionalization of the channel pores of ordered mesoporous silica, that of the silica framework, as well as the functionalization of both of them simultaneously. This family is currently one of the best supports for exploring polyfunctional materials, which can provide a route to interactive materials. The second family concerns lamellar hybrid organic-inorganic materials which is a new class of nanostructured materials. These materials were first obtained by self-assembly, as a result of van der Waals interactions of bridged organosilica precursors containing long alkylene chains during the sol-gel process, without any structure directing agent. This methodology has been extended to functional materials. It is also shown that such materials can be obtained from monosilylated precursors.
The novel generating algorithm and properties of hybrid-P-ary generalized bridge functions
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
In this paper, we develop novel non-sine functions, named hybrid-P-ary generalized bridge functions, based on the copy and shift methods. The generating algorithm of hybrid-P-ary generalized bridge functions is introduced based on the hybrid-P-ary generalized Walsh function's copy algorithm. The main property, product property, is also discussed. This function may be viewed as the generalization of the theory of bridge functions. And a lot of non-sine orthogonal functions are the special subset of these novel functions. The hybrid-P-ary generalized bridge functions can be used to search many unknown non-sine functions by defining different parameters.
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 materia
Varini, Nicola; Ceresoli, Davide; Martin-Samos, Layla; Girotto, Ivan; Cavazzoni, Carlo
2013-08-01
One of the most promising techniques used for studying the electronic properties of materials is based on Density Functional Theory (DFT) approach and its extensions. DFT has been widely applied in traditional solid state physics problems where periodicity and symmetry play a crucial role in reducing the computational workload. With growing compute power capability and the development of improved DFT methods, the range of potential applications is now including other scientific areas such as Chemistry and Biology. However, cross disciplinary combinations of traditional Solid-State Physics, Chemistry and Biology drastically improve the system complexity while reducing the degree of periodicity and symmetry. Large simulation cells containing of hundreds or even thousands of atoms are needed to model these kind of physical systems. The treatment of those systems still remains a computational challenge even with modern supercomputers. In this paper we describe our work to improve the scalability of Quantum ESPRESSO (Giannozzi et al., 2009 [3]) for treating very large cells and huge numbers of electrons. To this end we have introduced an extra level of parallelism, over electronic bands, in three kernels for solving computationally expensive problems: the Sternheimer equation solver (Nuclear Magnetic Resonance, package QE-GIPAW), the Fock operator builder (electronic ground-state, package PWscf) and most of the Car-Parrinello routines (Car-Parrinello dynamics, package CP). Final benchmarks show our success in computing the Nuclear Magnetic Response (NMR) chemical shift of a large biological assembly, the electronic structure of defected amorphous silica with hybrid exchange-correlation functionals and the equilibrium atomic structure of height Porphyrins anchored to a Carbon Nanotube, on many thousands of CPU cores.
Epoxy Resin Composite Based on Functional Hybrid Fillers
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Mariusz Oleksy
2014-08-01
Full Text Available A study was carried out involving the filling of epoxy resin (EP with bentonites and silica modified with polyhedral oligomeric silsesquioxane (POSS. The method of homogenization and the type of filler affect the functional and canceling properties of the composites was determined. The filler content ranged from 1.5% to 4.5% by mass. The basic mechanical properties of the hybrid composites were found to improve, and, in particular, there was an increase in tensile strength by 44%, and in Charpy impact strength by 93%. The developed hybrid composites had characteristics typical of polymer nanocomposites modified by clays, with a fine plate morphology of brittle fractures observed by SEM, absence of a plate separation peak in Wide Angles X-ray Scattering (WAXS curves, and an exfoliated structure observed by TEM.
Epoxy Resin Composite Based on Functional Hybrid Fillers
Oleksy, Mariusz; Szwarc-Rzepka, Karolina; Heneczkowski, Maciej; Oliwa, Rafał; Jesionowski, Teofil
2014-01-01
A study was carried out involving the filling of epoxy resin (EP) with bentonites and silica modified with polyhedral oligomeric silsesquioxane (POSS). The method of homogenization and the type of filler affect the functional and canceling properties of the composites was determined. The filler content ranged from 1.5% to 4.5% by mass. The basic mechanical properties of the hybrid composites were found to improve, and, in particular, there was an increase in tensile strength by 44%, and in Charpy impact strength by 93%. The developed hybrid composites had characteristics typical of polymer nanocomposites modified by clays, with a fine plate morphology of brittle fractures observed by SEM, absence of a plate separation peak in Wide Angles X-ray Scattering (WAXS) curves, and an exfoliated structure observed by TEM. PMID:28788177
Clustomesogens: Liquid Crystalline Hybrid Nanomaterials Containing Functional Metal Nanoclusters.
Molard, Yann
2016-08-16
Inorganic phosphorescent octahedral metal nanoclusters fill the gap between metal complexes and nanoparticles. They are finite groups of metal atoms linked by metal-metal bonds, with an exact composition and structure at the nanometer scale. As their phosphorescence internal quantum efficiency can approach 100%, they represent a very attractive class of molecular building blocks to design hybrid nanomaterials dedicated to light energy conversion, optoelectronic, display, lighting, or theragnostic applications. They are obtained as AnM6X(i)8X(a)6 ternary salt powders (A = alkali cation, M = Mo, Re, W, X(i): halogen inner ligand, X(a) = halogen apical ligand) by high temperature solid state synthesis (750-1200 °C). However, their ceramic-like behavior has largely restricted their use as functional components in the past. Since these last two decades, several groups, including ours, started to tackle the challenge of integrating them in easy-to-process materials. Within this context, we have extensively explored the nanocluster ternary salt specificities to develop a new class of self-organized hybrid organic-inorganic nanomaterials known as clustomesogens. These materials, combine the specific properties of nanoclusters (magnetic, electronic, luminescence) with the anisotropy-related properties of liquid crystals (LCs). This Account covers the research and development of clustomesogens starting from the design concepts and synthesis to their introduction in functional devices. We developed three strategies to build such hybrid super- or supramolecules. In the covalent approach, we capitalized on the apical ligand-metal bond iono-covalent character to graft tailor-made organic LC promoters on the {M6X(i)8}(n+) nanocluster cores. The supramolecular approach relies on the host-guest complexation of the ternary cluster salt alkali cations with functional crown ether macrocycles. We showed that the hybrid LC behavior depends on the macrocycles structural features
Nonempirical range-separated hybrid functionals for solids and molecules.
Energy Technology Data Exchange (ETDEWEB)
Skone, Jonathan H.; Govoni, Marco; Galli, Giulia
2016-06-03
Dielectric-dependent hybrid (DDH) functionals were recently shown to yield accurate energy gaps and dielectric constants for a wide variety of solids, at a computational cost considerably less than that of GW calculations. The fraction of exact exchange included in the definition of DDH functionals depends (self-consistently) on the dielectric constant of the material. Here we introduce a range-separated (RS) version of DDH functionals where short and long-range components are matched using system dependent, non-empirical parameters. We show that RS DDHs yield accurate electronic properties of inorganic and organic solids, including energy gaps and absolute ionization potentials. Furthermore we show that these functionals may be generalized to finite systems.
Nonempirical Range-separated Hybrid Functionals for Solids and Molecules
Skone, Jonathan H; Galli, Giulia
2016-01-01
Dielectric-dependent hybrid (DDH) functionals were recently shown to yield accurate energy gaps and dielectric constants for a wide variety of solids, at a computational cost considerably less than that of GW calculations. The fraction of exact exchange included in the definition of DDH functionals depends (self-consistently) on the dielectric constant of the material. Here we introduce a range-separated (RS) version of DDH functionals where short and long-range components are matched using system dependent, non-empirical parameters. We show that RS DDHs yield accurate electronic properties of inorganic and organic solids, including energy gaps and absolute ionization potentials. Furthermore we show that these functionals may be generalized to finite systems.
Nonempirical range-separated hybrid functionals for solids and molecules
Skone, Jonathan H.; Govoni, Marco; Galli, Giulia
2016-06-01
Dielectric-dependent hybrid (DDH) functionals were recently shown to yield accurate energy gaps and dielectric constants for a wide variety of solids, at a computational cost considerably less than that of GW calculations. The fraction of exact exchange included in the definition of DDH functionals depends (self-consistently) on the dielectric constant of the material. Here we introduce a range-separated (RS) version of DDH functionals where short- and long-range components are matched using system-dependent, nonempirical parameters. We show that RS-DDHs yield accurate electronic properties of inorganic and organic solids, including energy gaps and absolute ionization potentials. Furthermore we show that these functionals may be generalized to finite systems.
Hydrogels from biopolymer hybrid for biomedical, food, and functional food applications
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 st...
Band Anticrossing in Dilute Germanium Carbides Using Hybrid Functionals
Stephenson, Chad A; Qi, Meng; Penninger, Michael; Schneider, William; Wistey, Mark A
2014-01-01
Dilute germanium carbides (Ge1-xCx) offer a direct bandgap for compact silicon photonics, but widely varying results have been reported. This work uses ab initio simulations with HSE06 hybrid functionals and spin-orbit coupling to study the band structure behavior in the absence of defects. Contrary to Vegard's law, the conduction band minimum at k=0 is consistently found to decrease with increasing C content, while L and X valleys remain nearly unchanged. A vanishing bandgap was observed for all alloys with x>0.017. Conduction bands deviate from a constant-potential band anticrossing model except near the center of the Brillouin zone.
Targeted Gene Capture by Hybridization to Illuminate Ecosystem Functioning.
Ribière, Céline; Beugnot, Réjane; Parisot, Nicolas; Gasc, Cyrielle; Defois, Clémence; Denonfoux, Jérémie; Boucher, Delphine; Peyretaillade, Eric; Peyret, Pierre
2016-01-01
Microbial communities are extremely abundant and diverse on earth surface and play key role in the ecosystem functioning. Thus, although next-generation sequencing (NGS) technologies have greatly improved knowledge on microbial diversity, it is necessary to reduce the biological complexity to better understand the microorganism functions. To achieve this goal, we describe a promising approach, based on the solution hybrid selection (SHS) method for the selective enrichment in a target-specific biomarker from metagenomic and metatranscriptomic samples. The success of this method strongly depends on the determination of sensitive, specific, and explorative probes to assess the complete targeted gene repertoire. Indeed, in this method, RNA probes were used to capture large DNA or RNA fragments harboring biomarkers of interest that potentially allow to link structure and function of communities of interest.
Di Valentin, Cristiana; Pacchioni, Gianfranco
2014-11-18
, for a more accurate description of the oxide band gap and of the electron localization of the impurity states associated with dopants or defects, we resorted to the use of hybrid functionals (B3LYP), where a portion of exact exchange in the exchange-correlation functional partly corrects for the self-interaction error inherent in DFT. In many cases, the self-interaction correction is very important, and these results can lead to a completely different physical picture than that obtained using local or semilocal functionals. We analyzed the electronic transitions in terms of their transition energy levels, which provided a more accurate comparison with experimental spectroscopic data than Kohn-Sham eigenvalues. The effects of N-doping were similar among the three oxides that we considered. The nature of the impurity state is always localized at the dopant site, which may limit their application in photocatalytic processes. Photocatalytic systems require highly delocalized photoexcited carriers within the material to effectively trigger redox processes at the surface. The nature of the electronic states associated with the oxygen deficiency differed widely in the three investigated oxides. In ZnO1-x and WO3-x the electronic states resemble the typical F-centers in insulating oxides or halides, with the excess electron density localized at the vacancy site. However, TiO2 acts as a reducible oxide, and the removal of neutral oxygen atoms reduced Ti(4+) to Ti(3+).
Hybrid density functional theory band structure engineering in hematite.
Pozun, Zachary D; Henkelman, Graeme
2011-06-14
We present a hybrid density functional theory (DFT) study of doping effects in α-Fe(2)O(3), hematite. Standard DFT underestimates the band gap by roughly 75% and incorrectly identifies hematite as a Mott-Hubbard insulator. Hybrid DFT accurately predicts the proper structural, magnetic, and electronic properties of hematite and, unlike the DFT+U method, does not contain d-electron specific empirical parameters. We find that using a screened functional that smoothly transitions from 12% exact exchange at short ranges to standard DFT at long range accurately reproduces the experimental band gap and other material properties. We then show that the antiferromagnetic symmetry in the pure α-Fe(2)O(3) crystal is broken by all dopants and that the ligand field theory correctly predicts local magnetic moments on the dopants. We characterize the resulting band gaps for hematite doped by transition metals and the p-block post-transition metals. The specific case of Pd doping is investigated in order to correlate calculated doping energies and optical properties with experimentally observed photocatalytic behavior.
Long, Run; English, Niall J
2011-10-04
The electronic properties of anatase-TiO(2) codoped by N and P at different concentrations have been investigated via generalized Kohn-Sham theory with the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional for exchange-correlation in the context of density functional theory. At high doping concentrations, we find that the high photocatalytic activity of (N, P)-codoped anatase TiO(2) vis-à-vis the N-monodoped case can be rationalized by a double-hole-mediated coupling mechanism [Yin et al., Phys. Rev. Lett. 2011, 106, 066801] via the formation of an effective N-P bond. On the other hand, Ti(3+) and Ti(4+) ions' spin double-exchange results in more substantial gap narrowing for larger separations between N and P atoms. At low doping concentrations, double-hole-coupling is dominant, regardless of the N-P distance. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Study of Magnesium Diboride Clusters Using Hybrid Density Functional Theory
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D. Rodríguez
2007-12-01
Full Text Available Using hybrid density functional theory and a relatively large basis set, the lowest energy equilibrium structure, vibrational spectrum, and natural orbital analysis were obtained for magnesium diboride clusters [(MgB2x for x=1,2, and 3]. For comparison, boron clusters [BxÃ‚Â forÃ‚Â x=2,4,Ã‚Â andÃ‚Â 6] were also considered. The MgB2 and (MgB22 showed equilibrium structures with the boron atoms in arrangements similar to what was obtained for pure boron atoms, whereas, for (MgB23 a different arrangement of boron was obtained. From the population analysis, large electron density in the boron atoms forming the clusters was observed.
Multilayer crack-free hybrid coatings for functional devices
Islam, Shumaila; Bidin, Noriah; Riaz, Saira; Naseem, Shahzad; Marsin Sanagi, Mohd.; Imran, M.
2016-04-01
Porous acid catalyzed TiO2 single, SiO2-TiO2 hybrid, and TiO2/SiO2-TiO2/SiO2 multilayer coatings are synthesized and characterized for optical and electro-optical applications. The reflection value is reasonably reduced from the surface of the glass by integrating sol-gel based spin-coated single and multilayer thin films. Structurally, the films show uniform, crack-free, and porous nanofilms with good surface roughness of below 10 nm, which has potential for optical applications. Wide range tunability of refractive index (2.83 to 1.59) with more than 78% optical transparency is observed. The multilayered reflection profile is observed around 0.18%, so these coatings are desirable for optochemical functional devices.
A Hybrid Imperative and Functional Molecular Mechanics Application
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Thomas Deboni
1996-01-01
Full Text Available Molecular mechanics applications model the interactions among large ensembles of discrete particles. They are used where probabilistic methods are inadequate, such as drug chemistry. This methodology is difficult to parallelize with good performance, due to its poor locality, uneven partitions, and dynamic behavior. Imperative programs have been written that attempt this on shared and distributed memory machines. Given such a program, the computational kernel can be rewritten in Sisal, a functional programming language, and integrated with the rest of the imperative program under the Sisal Foreign Language Interface. This allows minimal effort and maximal return from parallelization work, and leaves the work appropriate to imperative implementation in its original form. We describe such an effort, focusing on the parts of the application that are appropriate for Sisal implementation, the specifics of mixed-language programming, and the complex performance behavior of the resulting hybrid code.
Global hybrids from the semiclassical atom theory satisfying the local density linear response
Fabiano, E; Cortona, P; Della Sala, F
2015-01-01
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. 106, 186406, (2011)] 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 energetical and structural testings, including thermochemistry and geometry, transition metal complexes, non-covalent 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\\% o...
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.
Directory of Open Access Journals (Sweden)
Cong Zhang
2015-01-01
Full Text Available Although both battery and super-capacitor are important power sources for hybrid electric vehicles, there is no accurate configuration theory to match the above two kinds of power sources which have significantly different characteristics on energy and power storage for the goal of making good use of their individual features without size wasting. In this paper, a new performance is presented that is used for analysis and optimal design method of battery and super-capacitor for hybrid energy storage system of a parallel hybrid electrical vehicle. In order to achieve optimal design with less consumption, the power-energy function is applied to establish direct mathematical relationship between demand power and the performance. During matching process, firstly, three typical operating conditions are chosen as the basis of design; secondly, the energy and power capacity evaluation methods for the parameters of battery and super-capacitor in hybrid energy storage system are proposed; thirdly, the mass, volume, and cost of the system are optimized simultaneously by using power-energy function. As a result, there are significant advantages on mass, volume, and cost for the hybrid energy storage system with the matching method. Simulation results fit well with the results of analysis, which confirms that the optimized design can meet the demand of hybrid electric vehicle well.
Oshima, Masamitsu; Inoue, Kaoru; Nakajima, Kei; Tachikawa, Tetsuhiko; Yamazaki, Hiromichi; Isobe, Tomohide; Sugawara, Ayaka; Ogawa, Miho; Tanaka, Chie; Saito, Masahiro; Kasugai, Shohei; Takano-Yamamoto, Teruko; Inoue, Takashi; Tezuka, Katsunari; Kuboki, Takuo; Yamaguchi, Akira; Tsuji, Takashi
2014-01-01
Bio-hybrid artificial organs are an attractive concept to restore organ function through precise biological cooperation with surrounding tissues in vivo. However, in bio-hybrid artificial organs, an artificial organ with fibrous connective tissues, including muscles, tendons and ligaments, has not been developed. Here, we have enveloped with embryonic dental follicle tissue around a HA-coated dental implant, and transplanted into the lower first molar region of a murine tooth-loss model. We successfully developed a novel fibrous connected tooth implant using a HA-coated dental implant and dental follicle stem cells as a bio-hybrid organ. This bio-hybrid implant restored physiological functions, including bone remodelling, regeneration of severe bone-defect and responsiveness to noxious stimuli, through regeneration with periodontal tissues, such as periodontal ligament and cementum. Thus, this study represents the potential for a next-generation bio-hybrid implant for tooth loss as a future bio-hybrid artificial organ replacement therapy.
Tran, Fabien; Blaha, Peter
2017-05-04
Recently, exchange-correlation potentials in density functional theory were developed with the goal of providing improved band gaps in solids. Among them, the semilocal potentials are particularly interesting for large systems since they lead to calculations that are much faster than with hybrid functionals or methods like GW. We present an exhaustive comparison of semilocal exchange-correlation potentials for band gap calculations on a large test set of solids, and particular attention is paid to the potential HLE16 proposed by Verma and Truhlar. It is shown that the most accurate potential is the modified Becke-Johnson potential, which, most noticeably, is much more accurate than all other semilocal potentials for strongly correlated systems. This can be attributed to its additional dependence on the kinetic energy density. It is also shown that the modified Becke-Johnson potential is at least as accurate as the hybrid functionals and more reliable for solids with large band gaps.
Arakaki, Atsushi; Shimizu, Katsuhiko; Oda, Mayumi; Sakamoto, Takeshi; Nishimura, Tatsuya; Kato, Takashi
2015-01-28
Organisms produce various organic/inorganic hybrid materials, which are called biominerals. They form through the self-organization of organic molecules and inorganic elements under ambient conditions. Biominerals often have highly organized and hierarchical structures from nanometer to macroscopic length scales, resulting in their remarkable physical and chemical properties that cannot be obtained by simple accumulation of their organic and inorganic constituents. These observations motivate us to create novel functional materials exhibiting properties superior to conventional materials--both synthetic and natural. Herein, we introduce recent progress in understanding biomineralization processes at the molecular level and the development of organic/inorganic hybrid materials by these processes. We specifically outline fundamental molecular studies on silica, iron oxide, and calcium carbonate biomineralization and describe material synthesis based on these mechanisms. These approaches allow us to design a variety of advanced hybrid materials with desired morphologies, sizes, compositions, and structures through environmentally friendly synthetic routes using functions of organic molecules.
Jacobian Elliptic Function Method and Solitary Wave Solutions for Hybrid Lattice Equation
Institute of Scientific and Technical Information of China (English)
WANG Rui-Min; DAI Chao-Qing; ZHANG Jie-Fang
2006-01-01
In this paper, we have successfully extended the Jacobian elliptic function expansion approach to nonlinear differential-difference equations. The Hybrid lattice equation is chosen to illustrate this approach. As a consequence,twelve families of Jacobian elliptic function solutions with different parameters of the Hybrid lattice equation are obtained.When the modulus m → 1 or 0, doubly-periodic solutions degenerate to solitonic solutions and trigonometric function solutions, respectively.
Tuned range separated hybrid functionals for solvated low bandgap oligomers
Energy Technology Data Exchange (ETDEWEB)
Queiroz, Thiago B. de, E-mail: thiago.branquinho-de-queiroz@uni-bayreuth.de; Kümmel, Stephan [Theoretical Physics IV, University of Bayreuth, D-95440 Bayreuth (Germany)
2015-07-21
The description of charge transfer excitations has long been a challenge to time dependent density functional theory. The recently developed concept of “optimally tuned range separated hybrid (OT-RSH) functionals” has proven to describe charge transfer excitations accurately in many cases. However, describing solvated or embedded systems is yet a challenge. This challenge is not only computational but also conceptual, because the tuning requires identifying a specific orbital, typically the highest occupied one of the molecule under study. For solvated molecules, this orbital may be delocalized over the solvent. We here demonstrate that one way of overcoming this problem is to use a locally projected self-consistent field diagonalization on an absolutely localized molecular orbital expansion. We employ this approach to determine ionization energies and the optical gap of solvated oligothiophenes, i.e., paradigm low gap systems that are of relevance in organic electronics. Dioxane solvent molecules are explicitly represented in our calculations, and the ambiguities of straightforward parameter tuning in solution are elucidated. We show that a consistent estimate of the optimal range separated parameter (ω) at the limit of bulk solvation can be obtained by gradually extending the solvated system. In particular, ω is influenced by the solvent beyond the first coordination sphere. For determining ionization energies, a considerable number of solvent molecules on the first solvation shell must be taken into account. We demonstrate that accurately calculating optical gaps of solvated systems using OT-RSH can be done in three steps: (i) including the chemical environment when determining the range-separation parameter, (ii) taking into account the screening due to the solvent, and (iii) using realistic molecular geometries.
One- and many-electron self-interaction error in local and global hybrid functionals
Schmidt, Tobias; Kümmel, Stephan
2016-04-01
Electronic self-interaction poses a fundamental challenge in density-functional theory. It greatly limits, e.g., the physical interpretation of eigenvalues as electron removal energies. We here investigate whether local hybrid functionals that are designed to be free from one-electron self-interaction lead to occupied Kohn-Sham eigenvalues and orbitals that approximate photoemission observables well. We compare the local hybrid results to the ones from global hybrid functionals that only partially counteract the self-interaction, and to the results that are obtained with a Perdew-Zunger-type self-interaction correction. Furthermore, we check whether being nominally free from one-electron self-interaction translates into a reduced many-electron self-interaction error. Our findings show that this is not the case for the local hybrid functionals that we studied: In practice they are similar to global hybrids in many respects, despite being formally superior. This finding indicates that there is a conceptual difference between the Perdew-Zunger way and the local hybrid way of translating the one-electron condition to a many-electron system. We also point out and solve some difficulties that occur when using local hybrid functionals in combination with pseudopotentials.
APPLICATION OF PENALTY FUNCTION METHOD IN ISOPARAMETRIC HYBRID FINITE ELEMENT ANALYSIS
Institute of Scientific and Technical Information of China (English)
CHEN Dao-zheng; JIAO Zhao-ping
2005-01-01
By the aid of the penalty function method, the equilibrium restriction conditions were introduced to the isoparametric hybrid finite element analysis, and the concrete application course of the penalty function method in three-dimensional isoparametric hybrid finite element was discussed. The separated penalty parameters method and the optimal hybrid element model with penalty balance were also presented.The penalty balance method can effectively refrain the parasitical stress on the premise of no additional degrees of freedom. The numeric experiment shows that the presented element not only is effective in improving greatly the numeric calculation precision of distorted grids but also has the universality.
Hybrid function method for solving Fredholm and Volterra integral equations of the second kind
Hsiao, Chun-Hui
2009-08-01
Numerical solutions of Fredholm and Volterra integral equations of the second kind via hybrid functions, are proposed in this paper. Based upon some useful properties of hybrid functions, integration of the cross product, a special product matrix and a related coefficient matrix with optimal order, are applied to solve these integral equations. The main characteristic of this technique is to convert an integral equation into an algebraic; hence, the solution procedures are either reduced or simplified accordingly. The advantages of hybrid functions are that the values of n and m are adjustable as well as being able to yield more accurate numerical solutions than the piecewise constant orthogonal function, for the solutions of integral equations. We propose that the available optimal values of n and m can minimize the relative errors of the numerical solutions. The high accuracy and the wide applicability of the hybrid function approach will be demonstrated with numerical examples. The hybrid function method is superior to other piecewise constant orthogonal functions [W.F. Blyth, R.L. May, P. Widyaningsih, Volterra integral equations solved in Fredholm form using Walsh functions, Anziam J. 45 (E) (2004) C269-C282; M.H. Reihani, Z. Abadi, Rationalized Haar functions method for solving Fredholm and Volterra integral equations, J. Comp. Appl. Math. 200 (2007) 12-20] for these problems.
Skin-inspired hydrogel-elastomer hybrids with robust interfaces and functional microstructures
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.
Skin-inspired hydrogel–elastomer hybrids with robust interfaces and functional microstructures
Yuk, Hyunwoo; Zhang, Teng; Parada, German Alberto; Liu, Xinyue; Zhao, Xuanhe
2016-01-01
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. PMID:27345380
Biomolecule-nanoparticle hybrids as functional units for nanobiotechnology.
Baron, Ronan; Willner, Bilha; Willner, Itamar
2007-01-28
Biomolecule-metal or semiconductor nanoparticle (NP) hybrid systems combine the recognition and catalytic properties of biomolecules with the unique electronic and optical properties of NPs. This enables the application of the hybrid systems in developing new electronic and optical biosensors, to synthesize nanowires and nanocircuits, and to fabricate new devices. Metal NPs are employed as nano-connectors that activate redox enzymes, and they act as electrical or optical labels for biorecognition events. Similarly, semiconductor NPs act as optical probes for biorecognition processes. Double-stranded DNA or protein chains that are modified with metallic nanoclusters act as templates for the synthesis of metallic nanowires. The nanowires are used as building blocks to assemble nano-devices such as a transistor or a nanotransporter.
Functional evaluation of ES-somatic cell hybrids in vitro and in vivo.
Sumer, Huseyin; Kim, Kitai; Liu, Jun; Ng, Kitwa; Daley, George Q; Verma, Paul J
2014-06-01
Embryonic stem cells (ESCs) have previously been reported to reprogram somatic cells following fusion. The resulting ES-somatic cell hybrids have been shown to adopt the transcriptional profile of ESCs, suggesting that the pluripotent program is dominant. ES-somatic cell hybrids have most characteristics of pluripotent cells in vitro; however, it remains unclear whether the somatic genome is an active partner in the hybrid cells or simply retained predominately as silent cargo. Furthermore, the functional properties of ES-somatic cell hybrids in vivo have been limited to studies on their contribution to teratomas and developing embryos/chimeras. The extent of their pluripotency remains largely unclear. Here we determined that the somatic genome is actively transcribed by generating ES-somatic cell hybrids using Rag2-deficient ESCs fused to autologous wild-type somatic cells. Rag2 expression was detected during in vitro differentiation, suggesting that the somatic genome follows the correct temporal cues during differentiation. Furthermore, ES-somatic cell hybrids maintain their tetraploid state following 4 weeks of differentiation in vivo and are immune tolerated when transferred into matched individuals. The ES-somatic cell hybrids can efficiently differentiate into hematopoietic precursors in both myeloid and lymphoid lineages in vitro, suggesting that the somatic genome is actively transcribed following cell fusion based reprogramming. However, the ES-somatic cell hybrids showed an altered hematopoietic potential following in vitro differentiation and were unable to show hematopoietic engraftment in a mouse model.
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.
Directory of Open Access Journals (Sweden)
Hideharu Mori
2012-01-01
Full Text Available This paper presents a short overview of recent advances in the design and synthesis of organic-inorganic hybrids using silsesquioxane-based nanoparticles having nanometer size, relatively narrow size distribution, high functionalities, and various characteristic features, mainly focusing on our recent researches related to the subject. A highlight of this paper is the water-soluble silsesquioxane-based nanoparticles, including hydroxyl-functionalized and cationic silsesquioxanes, which were synthesized via the one-step condensation of the bulky triethoxysilane precursors. The design and synthesis of R-SiO1.5/SiO2 and R-SiO1.5/TiO2 hybrids by hydrolytic cocondensation of a triethoxysilane precursor and metal alkoxides are briefly introduced. This paper also deals with recent results in stimuli-responsive hybrids based on the water-soluble silsesquioxane nanoparticles and fluorinated and amphiphilic silsesquioxane hybrids.
A New Hybrid MGBPSO-GSA Variant for Improving Function Optimization Solution in Search Space
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Narinder Singh
2017-03-01
Full Text Available In this article, a newly hybrid nature-inspired approach (MGBPSO-GSA is developed with a combination of Mean Gbest Particle Swarm Optimization (MGBPSO and Gravitational Search Algorithm (GSA. The basic inspiration is to integrate the ability of exploitation in MGBPSO with the ability of exploration in GSA to synthesize the strength of both approaches. As a result, the presented approach has the automatic balance capability between local and global searching abilities. The performance of the hybrid approach is tested on a variety of classical functions, ie, unimodal, multimodal, and fixed-dimension multimodal functions. Furthermore, Iris data set, Heart data set, and economic dispatch problems are used to compare the hybrid approach with several metaheuristics. Experimental statistical solutions prove empirically that the new hybrid approach outperforms significantly a number of metaheuristics in terms of solution stability, solution quality, capability of local and global optimum, and convergence speed.
Heart visualization based on hybrid transfer function using size and gradient.
Xia, Yong; Liu, Yixuan; Wang, Kuanquan
2014-01-01
Having the ability to visualize the heart clearly and precisely would be beneficial for pathology research, presurgical planning, and clinical approaches. Multi-dimensional transfer functions were employed to improve the overall performance of images. To provide a satisfactory visualization quality on the shape and boundaries of the heart, a new hybrid transfer function combining structure size with gradient was designed to highlight the area of the heart. Initially, a histogram of gradient and histogram of size was computed and then classification was performed for providing the spatial information. Finally, several hybrid strategies were presented for the design of the transfer function, including opacity and color. By experimental evaluation, the proposed hybrid transfer function visualized the cardiac outline and internal structure more clearly and easily.
Hydrogels from Biopolymer Hybrid for Biomedical, Food, and Functional Food Applications
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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.
Chai, Jeng-Da
2016-01-01
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 H2 dissociation 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 TAO-DFAs (i.e., TAO-DFT with the conventional density functional approximations), global hybrid...
A Comparative Study of Several Hybrid Particle Swarm Algorithms for Function Optimization
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Yanhua Zhong
2012-11-01
Full Text Available Currently, the researchers have made a lot of hybrid particle swarm algorithm in order to solve the shortcomings that the Particle Swarm Algorithms is easy to converge to local extremum, these algorithms declare that there has been better than the standard particle swarm. This study selects three kinds of representative hybrid particle swarm optimizations (differential evolution particle swarm optimization, GA particle swarm optimization, quantum particle swarm optimization and the standard particle swarm optimization to test with three objective functions. We compare evolutionary algorithm performance by a fixed number of iterations of the convergence speed and accuracy and the number of iterations under the fixed convergence precision; analyzing these types of hybrid particle swarm optimization results and practical performance. Test results show hybrid particle algorithm performance has improved significantly.
A Comparative Study of Several Hybrid Particle Swarm Algorithms for Function Optimization
Directory of Open Access Journals (Sweden)
Yanhua Zhong
2013-01-01
Full Text Available Currently, the researchers have made a lot of hybrid particle swarm algorithm in order to solve the shortcomings that the Particle Swarm Algorithms is easy to converge to local extremum, these algorithms declare that there has been better than the standard particle swarm. This study selects three kinds of representative hybrid particle swarm optimizations (differential evolution particle swarm optimization, GA particle swarm optimization, quantum particle swarm optimization and the standard particle swarm optimization to test with three objective functions. We compare evolutionary algorithm performance by a fixed number of iterations of the convergence speed and accuracy and the number of iterations under the fixed convergence precision, analyzing these types of hybrid particle swarm optimization results and practical performance. Test results show hybrid particle algorithm performance has improved significantly.
Toward a Representation of Hybrid Functional Petri Nets by MP Systems
Castellini, Alberto; Franco, Giuditta; Manca, Vincenzo
In this work we analyse and compare Hybrid Functional Petri Nets [10], an extension of Petri Nets [12] for biopathways simulation, and Metabolic P Systems [8,9]. An introduction to both of them is given, together with highlights about respective similarities and differences for biopathways modelling. The case study of glycolytic pathway with the lac operon gene regulatory mechanism was modeled by traditional Petri Nets in [6] and recently by Hybrid Functional Petri Nets in [10,4]. This model is here mapped into an MP system having the same dynamics.
Hybridization State Detection of DNA-Functionalized Gold Nanoparticles Using Hyperspectral Imaging
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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.
Hybrid input function estimation using a single-input-multiple-output (SIMO) approach
Su, Yi; Shoghi, Kooresh I.
2009-02-01
A hybrid blood input function (BIF) model that incorporates region of interests (ROIs) based peak estimation and a two exponential tail model was proposed to describe the blood input function. The hybrid BIF model was applied to the single-input-multiple-output (SIMO) optimization based approach for BIF estimation using time activity curves (TACs) obtained from ROIs defined at left ventricle (LV) blood pool and myocardium regions of dynamic PET images. The proposed BIF estimation method was applied with 0, 1 and 2 blood samples as constraints for BIF estimation using simulated small animal PET data. Relative percentage difference of the area-under-curve (AUC) measurement between the estimated BIF and the true BIF was calculated to evaluate the BIF estimation accuracy. SIMO based BIF estimation using Feng's input function model was also applied for comparison. The hybrid method provided improved BIF estimation in terms of both mean accuracy and variability compared to Feng's model based BIF estimation in our simulation study. When two blood samples were used as constraints, the percentage BIF estimation error was 0.82 +/- 4.32% for the hybrid approach and 4.63 +/- 10.67% for the Feng's model based approach. Using hybrid BIF, improved kinetic parameter estimation was also obtained.
Organic/inorganic hybrid nanomaterials with vitamin B12 functions
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Yoshio Hisaeda, Takahiro Masuko, Erika Hanashima and Takashi Hayashi
2006-01-01
Full Text Available A hybrid nanomaterial was prepared by human serum albumin (HSA and vitamin B12 derivatives. The incorporation of hydrophobic vitamin B12 derivatives, which have ester groups in place of the peripheral amide moieties of the natural cobalamin, into HSA is primarily controlled by the hydrophobicity of the peripheral ester groups. Microenvironmental property around the hydrophobic vitamin B12 in HSA was examined by fluorescence and fluorescence polarization measurements. The hydrophobic vitamin B12 itself in HSA is in a microenvironment equivalent in medium polarity to dichloromethane. The molecular motion of hydrophobic vitamin B12 in HSA was markedly suppressed under such microenvironmental conditions. Carbon-skeleton rearrangement reaction of an alkyl radical derived from an alkyl ligand bound to the hydrophobic vitamin B12 was markedly favored in HSA aqueous solution, relative to the reactions in methanol and benzene. The 1,2-migration of the electron-withdrawing group arises from both the suppression of molecular motion and desolvation effects on the alkylated hydrophobic vitamin B12 in HSA.
Mesoporous silica nanotubes hybrid membranes for functional nanofiltration
Energy Technology Data Exchange (ETDEWEB)
El-Safty, Sherif A; Shahat, Ahmed; Mekawy, Moataz; Nguyen, Hoa; Warkocki, Wojciech; Ohnuma, Masato, E-mail: sherif.elsafty@nims.go.jp, E-mail: sherif@aoni.waseda.jp [National Institute for Materials Science, Exploratory Materials Research Laboratory for Energy and Environment, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047 (Japan)
2010-09-17
The development of nanofiltration systems would greatly assist in the production of well-defined particles and biomolecules with unique properties. We report a direct, simple synthesis of hexagonal silica nanotubes (NTs), which vertically aligned inside anodic alumina membranes (AAM) by means of a direct templating method of microemulsion phases with cationic surfactants. The direct approach was used as soft templates for predicting ordered assemblies of surfactant/silica composites through strong interactions within AAM pockets. Thus, densely packed NTs were successfully formed in the entirety of the AAM channels. These silica NTs were coated with layers of organic moieties to create a powerful technique for the ultrafine filtration. The resulting modified-silica NTs were chemically robust and showed affinity toward the transport of small molecular particles. The rigid silica NTs inside AAM channels had a pore diameter of {<=} 4 nm and were used as ultrafine filtration systems for noble metal nanoparticles (NM NPs) and semiconductor nanocrystals (SC NCs) fabricated with a wide range of sizes (1.0-50 nm) and spherical/pyramidal morphologies. Moreover, the silica NTs hybrid membranes were also found to be suitable for separation of biomolecules such as cytochrome c (CytC). Importantly, this nanofilter design retains high nanofiltration efficiency of NM NPs, SC NCs and biomolecules after a number of reuse cycles. Such retention is crucial in industrial applications.
A hybrid method for the parallel computation of Green's functions
DEFF Research Database (Denmark)
Petersen, Dan Erik; Li, Song; Stokbro, Kurt;
2009-01-01
Quantum transport models for nanodevices using the non-equilibrium Green's function method require the repeated calculation of the block tridiagonal part of the Green's and lesser Green's function matrices. This problem is related to the calculation of the inverse of a sparse matrix. Because...
Yan, Bing; Qian, Kai
2009-01-01
A series of novel photoactive hybrid materials with organic parts covalently linked to inorganic parts via the acylamino group have been assembled by sol-gel process. The organic parts as molecular bridge derive from alpha-hydroxypyridine (HP) functionalized by 3-(triethoxysilyl)-propyl isocyanate (TESPIC). Finally homogeneous, molecular-based hybrid materials with different microstructure (uniform spherical or clubbed) are obtained, in which no phase separation is observed. This may be ascribed as the different coordination behavior of metal ions (Eu3+ (Tb3+) or Zn2+). Red emission of Eu-HP-Si, green emission of Tb-HP-Si and violet-blue luminescence of Zn-HP-Si hybrids can be achieved within these molecular-based hybrid materials. Besides, both Eu(Tb) and Zn are introduced into the same hybrid systems (Eu(Zn)-HP-Si or Tb(Zn)-HP-Si) through the covalent Si-O bond, whose sphere particle size can be modified. Especially the photoluminescence behavior can be enhanced, suggesting that intramolecular energy transfer takes place between inert Zn2+ and Eu3+ (Tb3+) in the covalently bonded hybrid systems.
Falcaro, Paolo; Costacurta, Stefano; Malfatti, Luca; Buso, Dario; Patelli, Alessandro; Schiavuta, Piero; Piccinini, Massimo; Grenci, Gianluca; Marmiroli, Benedetta; Amenitsch, Heinz; Innocenzi, Plinio
2011-02-01
A phenyl-based hybrid organic - inorganic coating has been synthesized and processed by hard X-ray lithography. The overall lithography process is performed in a two-step process only (X-rays exposure and chemical etching). The patterns present high aspect ratio, sharp edges, and high homogeneity. The coating has been doped with a variety of polycyclic aromatic hydrocarbon functional molecules, such as anthracene, pentacene, and fullerene. For the first time, hard X-rays have been combined with thick hybrid functional coatings, using the sol-gel thick film directly as resist. A new technique based on a new material combined with hard X-rays is now available to fabricate optical devices. The effect due to the high-energy photon exposure has been investigated using FT-IR and Raman spectroscopy, laser scanner, optical profilometer, and confocal and electron microscope. High-quality thick hybrid fullerene-doped microstructures have been fabricated.
Enhanced NLO response in BODIPY-coumarin hybrids: density functional theory approach
Indian Academy of Sciences (India)
YOGESH ERANDE; NAGAIYAN SEKAR
2017-09-01
We have thoroughly investigated the first, second and third polarizability characteristics of four hybrid chromophores by spectroscopic and computational methods. B3LYP, CAMB3LYP and BHandHLYP functionals in combination with 6-311+G(d,p) basis set were used to evaluate the polarizability and hyperpolarizability characteristics of these chromophores. Generalized Mulliken Hush analysis and frontier molecular orbital electronic distribution images of chromophores obtained from Density functional theory computation has established the charge transfer characteristics of these hybrid chromophores. On the basis of charge transfer characteristic, these red absorbing and NIR emissive chromophores possess high nonlinear optical response. Comparison of isolated units with their analogous hybrid chromophores shows that fusion ofcoumarin with BODIPY enhances the nonlinear optical response.
Grüning, M.; Gritsenko, O. V.; van Gisbergen, S. J. A.; Baerends, E. J.
2001-01-01
Shape corrections to the standard approximate Kohn-Sham exchange-correlation (xc) potentials are considered with the aim to improve the excitation energies (especially for higher excitations) calculated with time-dependent density functional perturbation theory. A scheme of gradient-regulated connection (GRAC) of inner to outer parts of a model potential is developed. Asymptotic corrections based either on the potential of Fermi and Amaldi or van Leeuwen and Baerends (LB) are seamlessly connected to the (shifted) xc potential of Becke and Perdew (BP) with the GRAC procedure, and are employed to calculate the vertical excitation energies of the prototype molecules N2, CO, CH2O, C2H4, C5NH5, C6H6, Li2, Na2, K2. The results are compared with those of the alternative interpolation scheme of Tozer and Handy as well as with the results of the potential obtained with the statistical averaging of (model) orbital potentials. Various asymptotically corrected potentials produce high quality excitation energies, which in quite a few cases approach the benchmark accuracy of 0.1 eV for the electronic spectra. Based on these results, the potential BP-GRAC-LB is proposed for molecular response calculations, which is a smooth potential and a genuine "local" density functional with an analytical representation.
Semilocal and Hybrid Density Embedding Calculations of Ground-State Charge-Transfer Complexes
Laricchia, S; Della Sala, F; 10.1063/1.4795825
2013-01-01
We apply the frozen density embedding method, using a full relaxation of embedded densities through a freeze-and-thaw procedure, to study the electronic structure of several benchmark ground-state charge-transfer complexes, in order to assess the merits and limitations of the approach for this class of systems. The calculations are performed using both semilocal and hybrid exchange-correlation (XC) functionals. The results show that embedding calculations using semilocal XC functionals yield rather large deviations with respect to the corresponding supermolecular calculations. Due to a large error cancellation effect, however, they can often provide a relatively good description of the electronic structure of charge-transfer complexes, in contrast to supermolecular calculations performed at the same level of theory. On the contrary, when hybrid XC functionals are employed, both embedding and supermolecular calculations agree very well with each other and with the reference benchmark results. In conclusion, fo...
Hydroxyapatite-Functionalized Graphene: A New Hybrid Nanomaterial
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C. Rodríguez-González
2014-01-01
Full Text Available Graphene oxide sheets (GO were functionalized with hydroxyapatite nanoparticles (nHAp through a simple and effective hydrothermal treatment and a novel physicochemical process. Microstructure and crystallinity were investigated by Fourier transform infrared spectroscopy (FT-IR, Raman spectroscopy, X-ray diffraction (XRD, ultraviolet-visible (UV-Vis absorption spectroscopy, and thermogravimetric analysis (TGA. Transmission electron microscopy (TEM and scanning electron microscopy (SEM were performed to characterize the morphology of the functionalized material. The resulting novel materials combine the biocompatibility of the nHAp with the strength and physical properties of the graphene.
Energy Technology Data Exchange (ETDEWEB)
Tussupbayev, Samat; Govind, Niranjan; Lopata, Kenneth A.; Cramer, Christopher J.
2015-03-10
We assess the performance of real-time time-dependent density functional theory (RT-TDDFT) for the calculation of absorption spectra of 12 organic dye molecules relevant to photovoltaics and dye sensitized solar cells with 8 exchange-correlation functionals (3 traditional, 3 global hybrids, and 2 range-separated hybrids). We compare the calculations with traditional linear-response (LR) TDDFT. In addition, we demonstrate the efficacy of the RT-TDDFT approach to calculate wide absorption spectra of two large chromophores relevant to photovoltaics and molecular switches.
Energy Technology Data Exchange (ETDEWEB)
Silverstein, Daniel W.; Govind, Niranjan; van Dam, Hubertus J. J.; Jensen, Lasse
2013-12-10
A parallel implementation of analytical time-dependent density functional theory gradients is presented for the quantum chemistry program NWChem. The implementation is based on the Lagrangian approach developed by Furche and Ahlrichs. To validate our implementation, we first calculate the Stokes shifts for a range of organic dye molecules using a diverse set of exchange-correlation functionals (traditional density functionals, global hybrids, and range-separated hybrids) followed by simulations of the one-photon absorption and resonance Raman scattering spectrum of the phenoxyl radical, the well-studied dye molecule rhodamine 6G, and a molecular host–guest complex (TTFcCBPQT^{4+}). The study of organic dye molecules illustrates that B3LYP and CAM-B3LYP generally give the best agreement with experimentally determined Stokes shifts unless the excited state is a charge transfer state. Absorption, resonance Raman, and fluorescence simulations for the phenoxyl radical indicate that explicit solvation may be required for accurate characterization. For the host–guest complex and rhodamine 6G, it is demonstrated that absorption spectra can be simulated in good agreement with experimental data for most exchange-correlation functionals. Finally, however, because one-photon absorption spectra generally lack well-resolved vibrational features, resonance Raman simulations are necessary to evaluate the accuracy of the exchange-correlation functional for describing a potential energy surface.
Theoretical study on stability of hybrid bilayers
Silva, Thiago S.; de Lima Bernardo, Bertúlio; Azevedo, Sèrgio
2015-04-01
Motivated by the recent experimental realization of the hybrid nanostructure of graphene and boron nitride (h-BN) sheet, and studies of gap modulation by strain, we use first principles calculations based on density functional theory to investigate the effects of strain in hybrid bilayers composed of two monolayers of graphene with a nanodomain of {{B}3}{{N}3}. The calculations were made with two different approximations for the functional exchange-correlation, GGA and VDW-DF. We investigate the modification in the electronic structure and structural properties of various configurations of the hybrid bilayers. Among the configurations, those with Bernal stacking are found to be more stable when compared to the others. Studies of the compressive strain influence were made only in the structure that has been shown to be the most stable. We have found that the two approximations used in the calculations exhibit the same results for the electronic properties of all structures. The opening of the energy gap due to strain was possible in the calculations by using the GGA approximation, but the same does not happen in the calculations using the VDW-DF approximation. Our analysis shows that the VDW-DF approximation is better suited for studies involving surfaces.
A hybrid fuzzy MCDM approach to maintenance Quality Function Deployment
Directory of Open Access Journals (Sweden)
Davy George Valavi
2015-01-01
Full Text Available Maintenance Quality Function Deployment (MQFD is a model, which enhances the synergic power of Quality Function Deployment (QFD and Total Productive Maintenance (TPM. One of the crucial and important steps during the implementation of MQFD is the determination of the importance or weightages of the critical factors (CF and sub factors (SF. The CFs and SFs have to be compared precisely for the successful implementation of MQFD. The crisp pair-wise comparison in the conventional Analytical Hierarchy Process (AHP may be insufficient to determine the degree of weightage of CFs and SFs where vagueness and uncetainties are associated. In this paper, a modification of AHP based MQFD by incorporating fuzzy operations is proposed, which can improve the accuracy of determination of the weightages. A case study showing the applicability of this method is illustrated in this paper.
Functionally Graded Multifunctional Hybrid Composites for Extreme Environments
2010-02-01
1AXn Phases (n = 1, 2 and 3) 211 312 413 Barsoum and El-Raghy, American Scientist 2001 Barsoum and El-Raghy, Met. Mat. Trans., 1999 Jeitschko and...layer Ti2AlC Ti2AlC block after hammer blows Ti3SiC2 1. Barsoum and El-Raghy, American Scientist , 2001 2. www.3one2.com AFOSR-MURI Functionally
Use of discrete Wigner functions in the study of a hybrid dissipative system
Reboiro, M.; Civitarese, O.; Ramirez, R.; Tielas, D.
2017-09-01
The persistence of coherence in a hybrid dissipative system, which is composed of superconducting flux-qubits (SFQs) and an electron ensemble, is analyzed. Both the interactions between the electrons and the SFQs are taken into account. The time evolution of the hybrid system is discussed in terms of the discrete Wigner function of each subsystem and in terms of the entropic uncertainty relations. The inclusion of a linewidth, both for the electrons and the SFQs, influences the coherence of each subsystem and the pattern of spin squeezing of the corresponding steady state.
Fessler, J A
1995-01-01
This paper describes rapidly converging algorithms for computing attenuation maps from Poisson transmission measurements using penalized-likelihood objective functions. We demonstrate that an under-relaxed cyclic coordinate-ascent algorithm converges faster than the convex algorithm of Lange (see ibid., vol.4, no.10, p.1430-1438, 1995), which in turn converges faster than the expectation-maximization (EM) algorithm for transmission tomography. To further reduce computation, one could replace the log-likelihood objective with a quadratic approximation. However, we show with simulations and analysis that the quadratic objective function leads to biased estimates for low-count measurements. Therefore we introduce hybrid Poisson/polynomial objective functions that use the exact Poisson log-likelihood for detector measurements with low counts, but use computationally efficient quadratic or cubic approximations for the high-count detector measurements. We demonstrate that the hybrid objective functions reduce computation time without increasing estimation bias.
Range-separated double-hybrid density-functional theory applied to periodic systems
Sansone, Giuseppe; Civalleri, Bartolomeo; Usvyat, Denis; Toulouse, Julien; Sharkas, Kamal; Maschio, Lorenzo
2015-01-01
International audience; Quantum chemistry methods exploiting density-functional approximations for short-range electron-electron interactions and second-order M{{\\o}}ller-Plesset (MP2) perturbation theory for long-range electron-electron interactions have been implemented for periodic systems using Gaussian-type basis functions and the local correlation framework. The performance of these range-separated double hybrids has been benchmarked on a significant set of systems including rare-gas, m...
A Numerical Method for Lane-Emden Equations Using Hybrid Functions and the Collocation Method
Directory of Open Access Journals (Sweden)
Changqing Yang
2012-01-01
Full Text Available A numerical method to solve Lane-Emden equations as singular initial value problems is presented in this work. This method is based on the replacement of unknown functions through a truncated series of hybrid of block-pulse functions and Chebyshev polynomials. The collocation method transforms the differential equation into a system of algebraic equations. It also has application in a wide area of differential equations. Corresponding numerical examples are presented to demonstrate the accuracy of the proposed method.
Garavand, Ali; Dadkhah Tehrani, Abbas
2016-11-05
Organic-inorganic functional hybrid materials play a major role in the development of advanced functional materials and recently have gained growing interest of the worldwide community. In this context, new hybrid organic-inorganic gel consisting of cellulose nanowhisker xanthate (CNWX) and S-H functionalized polypseudorotaxane (PPR) as organic parts of gel and gold nanorods (GNRs) as inorganic cross-linking agent were prepared. Firstly, thiolated α-cyclodextrin (α-CD-SH) was threaded onto poly-(ethylene glycol) bis (mercaptoethanoate ester) (PEG-SH) to give polypseudorotaxane (PPR) and then it reacted with GNRs in the presence of CNWX to give the new hybrid gel material. The new synthesized gel and its components characterized by spectroscopic measurement methods such as FT-IR, UV-vis and NMR spectroscopy. Interestingly, hybrid gel showed new polygonal plate like morphology with 45-60nm thickness and 400-600nm width. The obtained gel may have potential application in many fields especially in biomedical applications.
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.
Borgoo, Alex; Tozer, David J
2012-06-07
The influence of the asymptotic exchange-correlation potential and density-scaling homogeneity on negative electron affinities determined using the approach of Tozer and De Proft [J. Phys. Chem. A2005, 109, 8923] is investigated. Application of an asymptotic correction to the potential improves the accuracy for several of the systems with the most negative affinities, reflecting their diffuse lowest unoccupied orbitals. For systems with modest affinities, it reduces the accuracy marginally. Enforcing a near-exact effective homogeneity through a simple shift in the potential leads to improved correlation with experimental values but significantly overestimated affinities. Optimal effective homogeneities are therefore determined, and a simple scheme is proposed for enforcing an average optimal value. Application of the scheme to a series of organic molecules maintains the excellent correlation with the experimental values while significantly reducing the absolute errors.
Hybrid model decomposition of speech and noise in a radial basis function neural model framework
DEFF Research Database (Denmark)
Sørensen, Helge Bjarup Dissing; Hartmann, Uwe
1994-01-01
applied is based on a combination of the hidden Markov model (HMM) decomposition method, for speech recognition in noise, developed by Varga and Moore (1990) from DRA and the hybrid (HMM/RBF) recognizer containing hidden Markov models and radial basis function (RBF) neural networks, developed by Singer...... and Lippmann (1992) from MIT Lincoln Lab. The present authors modified the hybrid recognizer to fit into the decomposition method to achieve high performance speech recognition in noisy environments. The approach has been denoted the hybrid model decomposition method and it provides an optimal method...... for decomposition of speech and noise by using a set of speech pattern models and a noise model(s), each realized as an HMM/RBF pattern model...
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.
Institute of Scientific and Technical Information of China (English)
Qiu-shuang Gao; Guo-feng Tian; Sheng-li Qi; Zhan-peng Wu; De-zhen Wu
2013-01-01
Ladder-like polysilsesquioxanes (LPSQs) with different amino contents have been synthesized by controlling of the dosage of Pd/C catalyst.The concentration and activity of amino groups were investigated by Fourier transform infrared spectroscopy.Polyimide (PI)/LPSQ hybrid films have been prepared by incorporating of the obtained LPSQs with different amino contents into PI matrix,respectively.The interfacial interactions between PI matrix and LPSQ were studied with scanning electron microscopy and X-ray photoelectron spectroscopy,meanwhile the thermal and mechanical properties of the hybrid films were studied using dynamic mechanical analysis and tensile tests.The results indicate that the functionality of LPSQ has great effects on the interfacial interactions and the properties of hybrid films.With the increase of amino content,both the interracial interactions and the cross-linking density of hybrids enhanced,which results in the decline of surface silicon concentration,increase of Young's modulus and drop of elongation at break.Excessive amino content makes the hybrid films brittle and leads to incomplete imidization.
Sun, Hsiao-Ling; Chai, Jeng-Da
2015-01-01
We examine the performance of our recently developed LFAs-PBE exchange-correlation (XC) potential [C.-R. Pan, P.-T. Fang, and J.-D. Chai, Phys. Rev. A, 2013, 87, 052510] for the high-order harmonic generation (HHG) spectra and related properties of H2+ molecules aligned parallel and perpendicular to the polarization of an intense linearly polarized laser pulse, employing the real-time formulation of time-dependent density functional theory (RT-TDDFT). The results are compared with the exact solutions of the time-dependent Schr\\"odinger equation as well as those obtained with other XC potentials in RT-TDDFT. Owing to its correct $(-1/r)$ asymptote, the LFAs-PBE potential significantly outperforms conventional XC potentials for the HHG spectra and the properties that are sensitive to the XC potential asymptote. Accordingly, the LFAs-PBE potential, which has a computational cost similar to that of the popular Perdew-Burke-Ernzerhof (PBE) potential, can be very promising for the study of the ground-state, excited...
Importance of local exact exchange potential in hybrid functionals for accurate excited states
Kim, Jaewook; Hwang, Sang-Yeon; Ryu, Seongok; Choi, Sunghwan; Kim, Woo Youn
2016-01-01
Density functional theory has been an essential analysis tool for both theoretical and experimental chemists since accurate hybrid functionals were developed. Here we propose a local hybrid method derived from the optimized effective potential (OEP) method and compare its distinct features with conventional nonlocal ones from the Hartree-Fock (HF) exchange operator. Both are formally exact for ground states and thus show similar accuracy for atomization energies and reaction barrier heights. For excited states, the local version yields virtual orbitals with N-electron character, while those of the nonlocal version have mixed characters between N- and (N+1)-electron orbitals. As a result, the orbital energy gaps from the former well approximate excitation energies with a small mean absolute error (MAE = 0.40 eV) for the Caricato benchmark set. The correction from time-dependent density functional theory with a simple local density approximation kernel further improves its accuracy by incorporating multi-config...
Kataoka, Sho; Banerjee, Subhabrata; Kawai, Akiko; Kamimura, Yoshihiro; Choi, Jun-Chul; Kodaira, Tetsuya; Sato, Kazuhiko; Endo, Akira
2015-04-01
Layered organic-inorganic hybrid perovskites that consist of metal halides and organic interlayers are a class of low-dimensional materials. Here, we report the fabrication of layered hybrid perovskites using metal halides and silsesquioxane with a cage-like structure. We used a silsesquioxane as an interlayer to produce a rigid structure and improve the functionality of perovskite layers. Propylammonium-functionalized silsesquioxane and metal halide salts (CuCl2, PdCl2, PbCl2, and MnCl2) were self-assembled to form rigid layered perovskite structures with high crystallinity. The rigid silsesquioxane structure produces micropores between the perovskite layers that can potentially be filled with different molecules to tune the dielectric constants of the interlayers. The obtained silsesquioxane-metal halide hybrid perovskites exhibit some characteristic properties of layered perovskites including magnetic ordering (CuCl4(2-) and MnCl4(2-)) and excitonic absorption/emission (PbCl4(2-)). Our results indicate that inserting silsesquioxane interlayers into hybrid perovskites retains and enhances the low-dimensional properties of the materials.
Premnath, P; Tan, B; Venkatakrishnan, K
2015-12-01
We introduce a hybrid nanostructured biomaterial that is a combination of rare phases of immiscible gold and silicon oxide, functionalized via ultrafast laser synthesis. For the first time, we show cancer controlling properties of rare phases of gold silicides, which include Au7Si, Au5Si, Au0.7Si2.3 and Au8Si2. Conventionally, pure forms of gold and silicon/silicon oxide are extensively employed in targeted therapy and drug delivery systems due to their unique properties. While silicon and silicon oxide nanoparticles have shown biocompatibility, gold nanoparticles show conflicting results based on their size and material properties. Several studies have shown that gold and silicon combinations produce cell controlling properties, however, these studies were not able to produce a homogenous combination of gold and silicon, owing to its immiscibility. A homogenous combination of gold and silicon may potentially enable properties that have not previously been reported. We describe rare phased gold-silicon oxide nanostructured hybrid biomaterials and its unique cancer controlling properties, owing to material properties, concentration, size and density. The gold-silicon oxide nanostructured hybrid is composed of individual gold-silicon oxide nanoparticles in various concentrations of gold and silicon, some nanoparticles possess a gold-core and silicon-shell like structure. The individual nanoparticles are bonded together forming a three dimensional nanostructured hybrid. The interaction of the nanostructured hybrids with cervical cancer cells showed a 96% reduction in 24h. This engineered nanostructured hybrid biomaterial presents significant potential due to the combination of immiscible gold and silicon oxide in varying phases and can potentially satiate the current vacuum in cancer therapy.
Directory of Open Access Journals (Sweden)
Mohsen Alipour
2014-01-01
Full Text Available We introduce a new combination of Bernstein polynomials (BPs and Block-Pulse functions (BPFs on the interval [0, 1]. These functions are suitable for finding an approximate solution of the second kind integral equation. We call this method Hybrid Bernstein Block-Pulse Functions Method (HBBPFM. This method is very simple such that an integral equation is reduced to a system of linear equations. On the other hand, convergence analysis for this method is discussed. The method is computationally very simple and attractive so that numerical examples illustrate the efficiency and accuracy of this method.
Modeling on the size dependent properties of InP quantum dots: a hybrid functional study
Cho, Eunseog; Jang, Hyosook; Lee, Junho; Jang, Eunjoo
2013-05-01
Theoretical calculations based on density functional theory were performed to provide better understanding of the size dependent electronic properties of InP quantum dots (QDs). Using a hybrid functional approach, we suggest a reliable analytical equation to describe the change of energy band gap as a function of size. Synthesizing colloidal InP QDs with 2-4 nm diameter and measuring their optical properties was also carried out. It was found that the theoretical band gaps showed a linear dependence on the inverse size of QDs and gave energy band gaps almost identical to the experimental values.
VV and VO2 defects in silicon studied with hybrid density functional theory
Christopoulos, Stavros Richard G
2014-12-07
The formation of VO (A-center), VV and VO2 defects in irradiated Czochralski-grown silicon (Si) is of technological importance. Recent theoretical studies have examined the formation and charge states of the A-center in detail. Here we use density functional theory employing hybrid functionals to analyze the formation of VV and VO2 defects. The formation energy as a function of the Fermi energy is calculated for all possible charge states. For the VV and VO2 defects double negatively charged and neutral states dominate, respectively.
Ultrathin gold nanowire-functionalized carbon nanotubes for hybrid molecular sensing.
Cui, Huizhong; Hong, Chenglin; Ying, Andrew; Yang, Xinmai; Ren, Shenqiang
2013-09-24
Carbon nanotubes (CNTs) have shown great potential as sensing component in the electrochemical field effect transistor and optical sensors, because of their extraordinary one-dimensional electronic structure, thermal conductivity, and tunable and stable near-infrared emission. However, the insolubility of CNTs due to strong van der Waals interactions limits their use in the field of nanotechnology. In this study, we demonstrate that noncovalent ultrathin gold nanowires functionalized multiwalled carbon nanotube (GNW-CNT) hybrid sensing agents show highly efficient and selective immune molecular sensing in electrochemical and near-infrared photoacoustic imaging methods. A detection limit of 0.01 ng/mL for the alpha-fetoprotein (AFP) antigen with high selectivity is shown. The extraordinary optical absorption, thermal, and electric conductivity of hybrid GNW-CNTs presented in this study could be an effective tactic to integrate imaging, sensing, and treatment functionalities.
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.
Gould, Tim
2013-01-01
By considering the physics of non-interacting ensembles we better generalise the notion of `exact exchange' (EXX) to systems with fractional occupations in the frontier orbitals (called LEXX), in part by exploiting ambiguities in the definitions of `correlation', `exchange' and `Hartree' physics in ensemble systems. The LEXX is employed in an optimised effective potential (OEP) approach (OLEXX) to approximate groundstate energies, where it is bounded by the `ensemble EXX' (EEXX) energy and standard fractional OEXX energy via $E^{\\EEXX}\\leq E^{\\OLEXX} \\leq E^{\\OEXX}$. Analysis of the OLEXX explains the success of standard OEP methods for diatoms at large spacing, and why they can fail when both spins are allowed to be non-integer. The OLEXX is demonstrated on H, Li and Na with fractional electron number with improvements over OEXX for all cases.
Ge, Xiaochuan; Rocca, Dario; Gebauer, Ralph; Baroni, Stefano
2014-01-01
We present a new release of the turboTDDFT code featuring an implementation of hybrid functionals, a recently introduced pseudo-Hermitian variant of the Liouville-Lanczos approach to time-dependent density-functional perturbation theory, and a newly developed Davidson-like algorithm to compute selected interior eigenvalues/vectors of the Liouvillian super-operator. Our implementation is thoroughly validated against benchmark calculations performed on the cyanin (C$_{21}$O$_{11}$H$_{21}$) molecule using the Gaussian09 and turboTDDFT 1.0 codes.
A Dynamic Multistage Hybrid Swarm Intelligence Optimization Algorithm for Function Optimization
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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.
Liu, Rui; Hu, Jinyang; Zhu, Senqiang; Lu, Jiapeng; Zhu, Hongjun
2017-09-12
Recently, graphene-based materials have become well-known nonlinear optical materials for the potential application of laser protection. Two new graphene oxide-platinum complex (GO-Pt) hybrid materials (GO-Pt-1, GO-Pt-2) have been fabricated through covalent modification and electrostatic adsorption of different Pt complexes with GO. The structural and photophysical properties of the resultant hybrid materials were studied. The nonlinear optical properties and optical power limiting (OPL) performance of Pt complexes, GO, and GO-Pt hybrid materials were investigated by using Z-scan measurements at 532 nm. At the same transmittance, the results illustrate that functionalization of GO makes GO-Pt hybrid materials possess better nonlinear optical properties and OPL performance than individual Pt complexes and GO due to a combination of nonlinear scattering, nonlinear absorption, and photoinduced electron and energy transfer between GO and Pt complex moieties. Furthermore, the nonlinear optics and OPL performance of GO-Pt-2 are better than those of GO-Pt-1, due to not only the excellent optical limiting of Pt-2 and more molecules per area of GO but also the way of combination of Pt-2 and GO.
Long-Range Corrected Hybrid Density Functionals with Improved Dispersion Corrections
Lin, You-Sheng; Mao, Shan-Ping; Chai, Jeng-Da
2012-01-01
By incorporating the improved empirical atom-atom dispersion corrections from DFT-D3 [Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. J. Chem. Phys. 2010, 132, 154104], two long-range corrected (LC) hybrid density functionals are proposed. Our resulting LC hybrid functionals, omegaM06-D3 and omegaB97X-D3, are shown to be accurate for a very wide range of applications, such as thermochemistry, kinetics, noncovalent interactions, frontier orbital energies, fundamental gaps, and long-range charge-transfer excitations, when compared with common global and LC hybrid functionals. Relative to omegaB97X-D [Chai, J.-D.; Head-Gordon, M. Phys. Chem. Chem. Phys. 2008, 10, 6615], omegaB97X-D3 (reoptimization of omegaB97X-D with improved dispersion corrections) is shown to be superior for non-bonded interactions, and similar in performance for bonded interactions, while omegaM06-D3 is shown to be superior for general applications.
Li, Zongle; He, Chunying; Wang, Zhao; Gao, Yachen; Dong, Yongli; Zhao, Cheng; Chen, Zhimin; Wu, Yiqun; Song, Weina
2016-07-06
Tetracarboxylic Zn(ii) phthalocyanine-amino functionalized graphene oxide (ZnPcC4-NGO) hybrid materials have been prepared by a covalent functionalization method. The characterizations indicate that the amino-functionalization of GO has an important influence on the structure and photophysical properties of the ZnPcC4-NGO hybrid. The ZnPcC4-NGO hybrid exhibits enhanced photo-induced electron transfer or energy transfer (PET/ET), compared to the ZnPcC4 covalent functionalized GO (ZnPcC4-GO), owing to the presence of the extended sp(2) carbon configurations, along with the partial reduction of the NGO nanosheets and the introduction of electron-donating ethylenediamine. The nonlinear optical (NLO) properties of the hybrids were investigated using the Z-scan technique at 532 nm with 4 ns laser pulses. The results show that the efficient covalent functionalization and partial reduction of NGO cause the ZnPcC4-NGO hybrid to possess evidently larger NLO properties than the individual NGO, ZnPcC4 and the ZnPcC4-GO hybrid. The enhanced NLO performance can be attributed to the increased excited state absorption from the extended sp(2) carbon configurations of the NGO moiety, reverse saturable absorption arising from ZnPcC4 moiety, and the contribution of the efficient PET/ET process between the ZnPcC4 and NGO moieties in the hybrid.
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Nathan I. Hammer
2010-01-01
Full Text Available Semiconductor nanocrystals hybridized with functional ligands represent an important new class of composite nanomaterials. The development of these new nanoscale building blocks has intensified over the past few years and offer significant advantages in a wide array of applications. Functional ligands allow for incorporation of nanocrystals into areas where their unique photophysics can be exploited. Energy and charge transfer between the ligands and the nanocrystal also result in enhanced physical properties that can be tuned by the choice of ligand architecture. Here, progress in the development and applications involving this new class of composite materials will be discussed.
Computationally efficient double hybrid density functional theory using dual basis methods
Byrd, Jason N
2015-01-01
We examine the application of the recently developed dual basis methods of Head-Gordon and co-workers to double hybrid density functional computations. Using the B2-PLYP, B2GP-PLYP, DSD-BLYP and DSD-PBEP86 density functionals, we assess the performance of dual basis methods for the calculation of conformational energy changes in C$_4$-C$_7$ alkanes and for the S22 set of noncovalent interaction energies. The dual basis methods, combined with resolution-of-the-identity second-order M{\\o}ller-Plesset theory, are shown to give results in excellent agreement with conventional methods at a much reduced computational cost.
Vacancy formation in MoO3: hybrid density functional theory and photoemission experiments
Salawu, Omotayo Akande
2016-09-29
Molybdenum oxide (MoO3) is an important material that is being considered for numerous technological applications, including catalysis and electrochromism. In the present study, we apply hybrid density functional theory to investigate O and Mo vacancies in the orthorhombic phase. We determine the vacancy formation energies of different defect sites as functions of the electron chemical potential, addressing different charge states. In addition, we investigate the consequences of defects for the material properties. Ultraviolet photoemission spectroscopy is employed to study the valence band of stoichiometric and O defective MoO3. We show that O vacancies result in occupied in-gap states.
Excitons in solids with non-empirical hybrid time-dependent density-functional theory
Ullrich, Carsten; Yang, Zeng-Hui; Sottile, Francesco
2015-03-01
The Bethe-Salpeter equation (BSE) accurately describes the optical properties of solids, but is computationally expensive. Time-dependent density-functional theory (TDDFT) is more efficient, but standard functionals do not produce excitons in extended systems. We present a new, non-empirical hybrid TDDFT approach whose computational cost is much less than BSE, while the accuracy for both bound excitons and the continuum spectra is comparable to that of the BSE. Good performance is observed for both small-gap semiconductors and large-gap insulators. Work supported by NSF Grant DMR-1408904.
A-centers in silicon studied with hybrid density functional theory
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.
Long-Range Corrected Hybrid Density Functionals with Damped Atom-Atom Dispersion Corrections
Energy Technology Data Exchange (ETDEWEB)
Chai, Jeng-Da; Head-Gordon, Martin
2008-06-14
We report re-optimization of a recently proposed long-range corrected (LC) hybrid density functionals [J.-D. Chai and M. Head-Gordon, J. Chem. Phys. 128, 084106 (2008)] to include empirical atom-atom dispersion corrections. The resulting functional, {omega}B97X-D yields satisfactory accuracy for thermochemistry, kinetics, and non-covalent interactions. Tests show that for non-covalent systems, {omega}B97X-D shows slight improvement over other empirical dispersion-corrected density functionals, while for covalent systems and kinetics, it performs noticeably better. Relative to our previous functionals, such as {omega}B97X, the new functional is significantly superior for non-bonded interactions, and very similar in performance for bonded interactions.
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
A hybrid microsystem with separately functioned temperature controlling substrate and sample operating fluidic microchannel was developed to demonstrate a reconfigurable microfluidics scheme.The temperature controlling substrate integrated a micro heater and a temperature sensor by using traditional silicon-based micromechanical system(MEMS)technique,which guaranteed high performance and robust reliability for repeatable usage.The sample operating fluidic microchannel was prepared by poly-(dimethylsiloxane) (PDMS)based soft lithography technique,which made it cheap enough for disposable applications.The PDMS microchannel chip was attached to the temperature controlling substrate for reconfigurable thermal applications.A thin PDMS film was used to seal the microchannel and bridge the functionalized substrate and the sample inside the channel,which facilitated heat transferring and prevented sample contaminating the temperature controlling substrate.Demonstrated by a one dimensional thermal resistance model,the thin PDMS film was important for the present reconfiguration applications.Thermal performance of this hybrid microsystem was examined,and the experimental results demonstrated that the chip system could work stably over hours with temperature variation less than 0.1oC.Multiple PDMS microchannel chips were tested on one heating substrate sequentially with a maximum intra-chip temperature difference of 1.0oC.DNA extracted from serum of a chronic hepatitis B virus(HBV)patient was amplified by this hybrid microsystem and the gel electrophoresis result indicated that the present reconfigurable microfluidic scheme worked successfully.
Kim, Jun Young; Kim, Jeongyong; Joo, Jinsoo
2016-11-28
Two-dimensional (2-D) transition metal dichalcogenides, such as MoSsub>2sub>, WSesub>2sub>, and WSsub>2sub>, are promising materials for application in field effect transistors, optoelectronics, and sensing devices. In this study, 2-D WSesub>2sub> samples with various numbers of layers were hybridized with functionalized gold nanoparticles (Au-NPs) to achieve surface-enhanced Raman scattering (SERS). The nanoscale Raman and photoluminescence spectra of the WSesub>2sub> layers and WSesub>2sub>/Au-NP hybrids were measured using a high-resolution laser confocal microscope. The WSesub>2sub> exhibited distinct optical characteristics depending on the number of WSesub>2sub> layers. The intensities of the Raman characteristic modes of the WSesub>2sub> layers were significantly enhanced after hybridization with functionalized Au-NPs, indicating the SERS effect. The SERS effect weakened with increasing the number of WSesub>2sub> layers. The SERS effect was more pronounced for mono- and bi-layer WSesub>2sub> systems compared with the multi-layer WSesub>2sub> systems.
Bi, Sai; Zhou, Hong; Zhang, Shusheng
2009-10-07
A signal amplification strategy based on bio-bar-code functionalized magnetic nanoparticles as labels holds promise to improve the sensitivity and detection limit of the detection of DNA hybridization and single-nucleotide polymorphisms by flow injection chemiluminescence assays.
Hybrid graded element model for transient heat conduction in functionally graded materials
Institute of Scientific and Technical Information of China (English)
Lei-Lei Cao; Qing-Hua Qin; Ning Zhao
2012-01-01
This paper presents a hybrid graded element model for the transient heat conduction problem in functionally graded materials (FGMs).First,a Laplace transform approach is used to handle the time variable.Then,a fundamental solution in Laplace space for FGMs is constructed.Next,a hybrid graded element is formulated based on the obtained fundamental solution and a frame field.As a result,the graded properties of FGMs are naturally reflected by using the fundamental solution to interpolate the intra-element field.Further,Stefest's algorithm is employed to convert the results in Laplace space back into the time-space domain.Finally,the performance of the proposed method is assessed by several benchmark examples.The results demonstrate well the efficiency and accuracy of the proposed method.
Organic-inorganic hybrid foams with diatomite addition: Effect on functional properties
Verdolotti, L.; D'Auria, M.; Lavorgna, M.; Vollaro, P.; Iannace, S.; Capasso, I.; Galzerano, B.; Caputo, D.; Liguori, B.
2016-05-01
Organic-inorganic hybrid foams were prepared by using metakaolin, diatomite as a partial (or total) replacement of metakaolin, as matrix, silicon and whipped protein as pore forming. The foamed systems were hardened at defined temperature and time and then characterized by mechanical point of view through compression tests and by functional point of view through fire reaction and acoustic tests. The experimental findings highlighted that the replacement of diatomite in the formulation affected the morphological structure of the foams and consequently their mechanical properties. In particular, the consolidation mechanism in the diatomite based-hybrid foams changed from geopolymerization to a silicate polycondensation mechanism. Therefore, mechanical performances enhanced with increasing of the diatomite content. Fire reaction tests, such as non-combustibility and cone calorimeter tests, showed positive thermal inertia of samples regardless of the content of diatomite.
Institute of Scientific and Technical Information of China (English)
LI LeLe; SUN LingDong; ZHANG YaWen; YAN ChunHua
2009-01-01
Since the discovery of a surfactant directed self-assembly approach for the fabrication of mesoporous silica in 1992,increasing attention has been focused on the design and synthesis of mesostructured functional materials.Organic functionalization is becoming a major topic in this research field,since highly ordered mesostructured organic-inorganic hybrids offer novel functionalities and enhanced performance over their individual components.We begin with a brief overview of the three fundamental methods (post-synthetic grafting technique,co-condensation method,and preparation of periodic mesoporous organosilicas) for the preparation of organically functionalized mesostructured silica,and focus on one of the most promising approaches,which herein was named as functional-template directed self-assembly (FTDSA) approach,and in the eyes of the authors it has a special position in the preparation of this class of hybrid materials.A comprehensive overview of the state of research in the area of FTDSA and its potential applications will be given.
Verma, Harish Kumar; Jain, Cheshta
2016-09-01
In this article, a hybrid algorithm of particle swarm optimization (PSO) with statistical parameter (HSPSO) is proposed. Basic PSO for shifted multimodal problems have low searching precision due to falling into a number of local minima. The proposed approach uses statistical characteristics to update the velocity of the particle to avoid local minima and help particles to search global optimum with improved convergence. The performance of the newly developed algorithm is verified using various standard multimodal, multivariable, shifted hybrid composition benchmark problems. Further, the comparative analysis of HSPSO with variants of PSO is tested to control frequency of hybrid renewable energy system which comprises solar system, wind system, diesel generator, aqua electrolyzer and ultra capacitor. A significant improvement in convergence characteristic of HSPSO algorithm over other variants of PSO is observed in solving benchmark optimization and renewable hybrid system problems.
Wang, Xinquan; Dvorac, Marc; Wu, Zhigang
2016-11-01
Hybrid functionals mixing the exact exchange with (semi)local functionals to reinstall the missing derivative discontinuity have been successfully employed to predict band gaps (Eg) in bulk semiconductors. Here we show that traditional hybrid functionals with fixed fractions of exact exchange do not perform significantly better than the most popular semilocal PBE-GGA functional for Eg of semiconductor nanostructures, since their band-gap corrections are essentially size independent. This is because they cannot respond properly to the variation in screening when size changes. They merely predict constant band-gap corrections to the PBE gaps in silicon nanowires (Si NWs) when wire diameter reduces, instead of the dramatic increase predicted by many-body G W calculations. Moreover, these hybrid functionals generate almost identical wave functions compared with PBE for both bulk Si and Si NWs, whose overlaps with corresponding quasiparticle wave functions become much smaller than 1 for narrow NWs.
Two-component hybrid time-dependent density functional theory within the Tamm-Dancoff approximation
Energy Technology Data Exchange (ETDEWEB)
Kühn, Michael [Institut für Physikalische Chemie, Karlsruher Institut für Technologie, Kaiserstraße 12, 76131 Karlsruhe (Germany); Weigend, Florian, E-mail: florian.weigend@kit.edu [Institut für Physikalische Chemie, Karlsruher Institut für Technologie, Kaiserstraße 12, 76131 Karlsruhe (Germany); Institut für Nanotechnologie, Karlsruher Institut für Technologie, Postfach 3640, 76021 Karlsruhe (Germany)
2015-01-21
We report the implementation of a two-component variant of time-dependent density functional theory (TDDFT) for hybrid functionals that accounts for spin-orbit effects within the Tamm-Dancoff approximation (TDA) for closed-shell systems. The influence of the admixture of Hartree-Fock exchange on excitation energies is investigated for several atoms and diatomic molecules by comparison to numbers for pure density functionals obtained previously [M. Kühn and F. Weigend, J. Chem. Theory Comput. 9, 5341 (2013)]. It is further related to changes upon switching to the local density approximation or using the full TDDFT formalism instead of TDA. Efficiency is demonstrated for a comparably large system, Ir(ppy){sub 3} (61 atoms, 1501 basis functions, lowest 10 excited states), which is a prototype molecule for organic light-emitting diodes, due to its “spin-forbidden” triplet-singlet transition.
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.
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.
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.
Zhong, Y D; Sun, X Y; Liu, E Y; Li, Y Q; Gao, Z; Yu, F X
2016-06-24
Liriodendron hybrids (Liriodendron chinense x L. tulipifera) are important landscaping and afforestation hardwood trees. To date, little genomic research on adventitious rooting has been reported in these hybrids, as well as in the genus Liriodendron. In the present study, we used adventitious roots to construct the first cDNA library for Liriodendron hybrids. A total of 5176 expressed sequence tags (ESTs) were generated and clustered into 2921 unigenes. Among these unigenes, 2547 had significant homology to the non-redundant protein database representing a wide variety of putative functions. Homologs of these genes regulated many aspects of adventitious rooting, including those for auxin signal transduction and root hair development. Results of quantitative real-time polymerase chain reaction showed that AUX1, IRE, and FB1 were highly expressed in adventitious roots and the expression of AUX1, ARF1, NAC1, RHD1, and IRE increased during the development of adventitious roots. Additionally, 181 simple sequence repeats were identified from 166 ESTs and more than 91.16% of these were dinucleotide and trinucleotide repeats. To the best of our knowledge, the present study reports the identification of the genes associated with adventitious rooting in the genus Liriodendron for the first time and provides a valuable resource for future genomic studies. Expression analysis of selected genes could allow us to identify regulatory genes that may be essential for adventitious rooting.
The resilient hybrid fiber sensor network with self-healing function.
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.
Kumar Pramanik, Sumit; Losada-Pérez, Patricia; Reekmans, Gunter; Carleer, Robert; D'Olieslaeger, Marc; Vanderzande, Dirk; Adriaensens, Peter; Ethirajan, Anitha
2017-04-01
With recent advances in the field of diagnostics and theranostics, liposomal technology has secured a fortified position as a potential nanocarrier. Specifically, radiation/photo-sensitive liposomes containing photo-polymerizable cross-linking lipids are intriguing as they can impart the vesicles with highly interesting properties such as response to stimulus and improved shell stability. In this work, 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphoethanolamine (DTPE) is used as a photo-polymerizable lipid to form functional hybrid-liposomes as it can form intermolecular cross-linking through the diacetylenic groups. Hybrid-liposomes were formulated using mixtures of DTPE and saturated lipids of different chain lengths (dipalmitoylphosphatidylcholine (DPPC) and dimirystoilphosphatidylcholine (DMPC)) at different molar ratios. The physico-chemical characteristics of the liposomes has been studied before and after UV irradiation using a combination of techniques: DSC, QCM-D and solid-state NMR. The results signify the importance of a subtle modification in alkyl chain length on the phase behavior of the hybrid-liposomes and on the degree of crosslinking in the shell.
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
G-centers in irradiated silicon revisited: A screened hybrid density functional theory approach
Wang, H.
2014-05-13
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-center in silicon (Si). The G-center is one of the most important radiation related defects in Czochralski grown Si. We systematically investigate the density of states and formation energy for different types of CiCs defects with respect to the Fermi energy for all possible charge states. Prevalence of the neutral state for the C-type defect is established.
Collision avoidance for a mobile robot based on radial basis function hybrid force control technique
Institute of Scientific and Technical Information of China (English)
Wen Shu-Huan
2009-01-01
Collision avoidance is always difficult in the planning path for a mobile robot. In this paper, the virtual force field between a mobile robot and an obstacle is formed and regulated to maintain a desired distance by hybrid force control algorithm. Since uncertainties from robot dynamics and obstacle degrade the performance of a collision avoidance task, intelligent control is used to compensate for the uncertainties. A radial basis function (RBF) neural network is used to regulate the force field of an accurate distance between a robot and an obstacle in this paper and then simulation studies are conducted to confirm that the proposed algorithm is effective.
Wen, Shu-Huan
2009-10-01
Collision avoidance is always difficult in the planning path for a mobile robot. In this paper, the virtual force field between a mobile robot and an obstacle is formed and regulated to maintain a desired distance by hybrid force control algorithm. Since uncertainties from robot dynamics and obstacle degrade the performance of a collision avoidance task, intelligent control is used to compensate for the uncertainties. A radial basis function (RBF) neural network is used to regulate the force field of an accurate distance between a robot and an obstacle in this paper and then simulation studies are conducted to confirm that the proposed algorithm is effective.
Hybrid density functional theory description of N- and C-doping of NiO.
Nolan, Michael; Long, Run; English, Niall J; Mooney, Damian A
2011-06-14
The large intrinsic bandgap of NiO hinders its potential application as a photocatalyst under visible-light irradiation. In this study, we have performed first-principles screened exchange hybrid density functional theory with the HSE06 functional calculations of N- and C-doped NiO to investigate the effect of doping on the electronic structure of NiO. C-doping at an oxygen site induces gap states due to the dopant, the positions of which suggest that the top of the valence band is made up primarily of C 2p-derived states with some Ni 3d contributions, and the lowest-energy empty state is in the middle of the gap. This leads to an effective bandgap of 1.7 eV, which is of potential interest for photocatalytic applications. N-doping induces comparatively little dopant-Ni 3d interactions, but results in similar positions of dopant-induced states, i.e., the top of the valence band is made up of dopant 2p states and the lowest unoccupied state is the empty gap state derived from the dopant, leading to bandgap narrowing. With the hybrid density functional theory (DFT) results available, we discuss issues with the DFT corrected for on-site Coulomb description of these systems.
Cho, Kie Yong; Yeom, Yong Sik; Seo, Heun Young; Park, Young Hun; Jang, Ha Na; Baek, Kyung-Youl; Yoon, Ho Gyu
2015-05-13
The design of amphiphilic polymer compatibilizers for solubility manipulation of CNT composites was systematically generalized in this study. Structurally tailored multiamphiphilic compatibilizer were designed and synthesized by applying simple, high-yield reactions. This multiamphiphilic compatibilizer was applied for noncovalent functionalization of CNTs as well as provided CNTs with outstanding dispersion stability, manipulation of solubility, and hybridization with Ag nanoparticles (NPs). With regard to the dispersion properties, superior records in maximum concentration (2.88-3.10 mg/mL in chloroform), and mass ratio of the compatibilizer for good CNT dispersion (36 wt %) were achieved by MWCNTs functionalized with a multiamphiphilic block copolymer compatibilizer. In particular, the solubility limitations of MWCNT dispersion in solvents ranging from toluene (nonpolar) to aqueous solution (polar) are surprisingly resolved by introducing this multiamphiphilic polymer compatibilizer. Furthermore, this polymer compatibilizer allowed the synthesis of the hybrid CNT nanocomposites with Ag nanoparticles by an in situ nucleation process. As such, the multiamphiphilic compatibilizer candidate as a new concept for the noncovalent functionalization of CNTs can extend their use for a wide range of applications.
Electronic structure modeling of InAs/GaSb superlattices with hybrid density functional theory
Garwood, T.; Modine, N. A.; Krishna, S.
2017-03-01
The application of first-principles calculations holds promise for greatly improving our understanding of semiconductor superlattices. Developing a procedure to accurately predict band gaps using hybrid density functional theory 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%.
Brea, Roberto J.; Hardy, Michael D.; Devaraj, Neal K.
2015-01-01
There has been increasing interest in utilizing bottom-up approaches to develop synthetic cells. A popular methodology is the integration of functionalized synthetic membranes with biological systems, producing “hybrid” artificial cells. This Concept article covers recent advances and the current state-of-the-art of such hybrid systems. Specifically, we describe minimal supramolecular constructs that faithfully mimic the structure and/or function of living cells, often by controlling the assembly of highly ordered membrane architectures with defined functionality. These studies give us a deeper understanding of the nature of living systems, bring new insights into the origin of cellular life, and provide novel synthetic chassis for advancing synthetic biology. PMID:26149747
Energy Technology Data Exchange (ETDEWEB)
Lee, C.C.; Ku, W.; Hsueh, H.C.
2010-08-30
Within the framework of time-dependent density-functional theory (TDDFT), we derive the dynamical linear response of local-density approximation plus U functional and benchmark it on NiO, a prototypical Mott insulator. Formulated using real-space Wannier functions, our computationally inexpensive framework gives detailed insights into the formation of tightly bound Frenkel excitons with reasonable accuracy. Specifically, a strong hybridization of multiple excitons is found to significantly modify the exciton properties. Furthermore, our study exposes a significant generic limitation of adiabatic approximation in TDDFT with hybrid functionals and in existing Bethe-Salpeter-equation approaches, advocating the necessity of strongly energy-dependent kernels in future development.
Kesharwani, Manoj Kumar; Martin, Jan M L
2015-01-01
We have compared the performance of Grimme style DH/DSD and Zhang-Xu-Goddard type xDH/xDSD forms for double hybrids. In the DH and DSD forms, KS orbitals with elevated HF exchange and damped DFT correlation are used, while in the xDH and xDSD forms, the KS orbitals are obtained from a conventional hybrid functional with undamped DFT correlation. Generally, the difference in performance between DSD and xDSD functionals is small, slightly favoring xDSD. Augmentation of the xDH form with either same-spin MP2 correlation or a dispersion correction markedly improves performance. Best xDSD results appear to be obtained for orbitals obtained with `exact exchange' fractions in the 50-70% range. The orbitals for xDSD appear to be fairly transferable between different correlation functionals.
Synthesis and Properties of Cellulose-Functionalized POSS-SiO2/TiO2 Hybrid Composites.
Hong, Gwang-Wook; Ramesh, Sivalingam; Kim, Joo-Hyung; Kim, Hyeon-Ju; Lee, Ho-Saeng
2015-10-01
The mechanical, thermal, optical, electrical and morphological properties of cellulose, an excellent natural biomaterial, can be improved by organic-inorganic hybrid composite methods. Based on the pristine properties of cellulose, the preparation of cellulose-metal oxide hybrid nanocomposites using a dispersion process of nanoparticles into the cellulose host matrix by traditional methods, has limitations. Recently, the functionalized cellulose-polymer-based materials were considered to be an important class of high-performance materials, providing the synthesis of various functional hybrid nanocomposites using a sol-gel method. Transparent cellulose-POSS-amine-silica/titania hybrids were prepared by an in-situ sol-gel process in the presence of γ-aminopropyltrimethoxylsilane (γ-APTES). The methodology involves the formation of covalent bonding between the cellulose-POSS amine and SiO2/TiO2 hybrid nanocomposite material. An analysis of the synthesized hybrid material by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, differential thermal calorimetry, scanning electron microscopy, and transmission electron microscopy indicated that the silica/titania nanoparticles were bonded covalently and dispersed uniformly into the cellulose-POSS amine matrix. In addition, biological properties of the cellulose-POSS-silica/titania hybrid material were examined using an antimicrobial test against pathogenic bacteria, such as Bacillus cereus (F481072) and E. coli (ATCC35150) for the bacterial effect.
Moshonov, Moshe; Frey, Gitti L
2015-11-24
The simplicity and versatility of block copolymer self-assembly offers their use as templates for nano- and meso-structured materials. However, in most cases, the material processing requires multiple steps, and the block copolymer is a sacrificial building block. Here, we combine a self-assembled block copolymer template and atomic layer deposition (ALD) of a metal oxide to generate functional hybrid films in a simple process with no etching or burning steps. This approach is demonstrated by using the crystallization-induced self-assembly of a rod-coil block copolymer, P3HT-b-PEO, and the ALD of ZnO. The block copolymer self-assembles into fibrils, ∼ 20 nm in diameter and microns long, with crystalline P3HT cores and amorphous PEO corona. The affinity of the ALD precursors to the PEO corona directs the exclusive deposition of crystalline ZnO within the PEO domains. The obtained hybrid structure possesses the properties desired for photovoltaic films: donor-acceptor continuous nanoscale interpenetrated networks. Therefore, we integrated the films into single-layer hybrid photovoltaics devices, thus demonstrating that combining self-assembly of functional block copolymers and ALD is a simple approach to direct desired complex hybrid morphologies.
Chung, Kyung-Hoon; Koo, Bon-Gil; Kim, Howon; Yoon, Jong Keon; Kim, Ji-Hoon; Kwon, Young-Kyun; Kahng, Se-Jong
2012-05-28
The electronic structures of self-assembled hybrid chains comprising Ag atoms and organic molecules were studied using scanning tunneling microscopy (STM) and spectroscopy (STS) in parallel with density functional theory (DFT). Hybrid chains were prepared by catalytic breaking of Br-C bonds in 4,4″-dibromo-p-terphenyl molecules, followed by spontaneous formation of Ag-C bonds on Ag(111). An atomic model was proposed for the observed hybrid chain structures. Four electronic states were resolved using STS measurements, and strong energy dependence was observed in STM images. These results were explained using first-principles calculations based on DFT.
A new hybrid genetic algorithm for optimizing the single and multivariate objective functions
Energy Technology Data Exchange (ETDEWEB)
Tumuluru, Jaya Shankar [Idaho National Laboratory; McCulloch, Richard Chet James [Idaho National Laboratory
2015-07-01
In this work a new hybrid genetic algorithm was developed which combines a rudimentary adaptive steepest ascent hill climbing algorithm with a sophisticated evolutionary algorithm in order to optimize complex multivariate design problems. By combining a highly stochastic algorithm (evolutionary) with a simple deterministic optimization algorithm (adaptive steepest ascent) computational resources are conserved and the solution converges rapidly when compared to either algorithm alone. In genetic algorithms natural selection is mimicked by random events such as breeding and mutation. In the adaptive steepest ascent algorithm each variable is perturbed by a small amount and the variable that caused the most improvement is incremented by a small step. If the direction of most benefit is exactly opposite of the previous direction with the most benefit then the step size is reduced by a factor of 2, thus the step size adapts to the terrain. A graphical user interface was created in MATLAB to provide an interface between the hybrid genetic algorithm and the user. Additional features such as bounding the solution space and weighting the objective functions individually are also built into the interface. The algorithm developed was tested to optimize the functions developed for a wood pelleting process. Using process variables (such as feedstock moisture content, die speed, and preheating temperature) pellet properties were appropriately optimized. Specifically, variables were found which maximized unit density, bulk density, tapped density, and durability while minimizing pellet moisture content and specific energy consumption. The time and computational resources required for the optimization were dramatically decreased using the hybrid genetic algorithm when compared to MATLAB's native evolutionary optimization tool.
Range-separated double-hybrid density-functional theory applied to periodic systems
Sansone, Giuseppe; Usvyat, Denis; Toulouse, Julien; Sharkas, Kamal; Maschio, Lorenzo
2015-01-01
Quantum chemistry methods exploiting density-functional approximations for short-range electron-electron interactions and second-order M{{\\o}}ller-Plesset (MP2) perturbation theory for long-range electron-electron interactions have been implemented for periodic systems using Gaussian-type basis functions and the local correlation framework. The performance of these range-separated double hybrids has been benchmarked on a significant set of systems including rare-gas, molecular, ionic, and covalent crystals. The use of spin-component-scaled MP2 for the long-range part has been tested as well. The results show that the value of $\\mu$ = 0.5 bohr^{--1} for the range-separation parameter usually used for molecular systems is also a reasonable choice for solids. Overall, these range-separated double hybrids provide a good accuracy for binding energies using basis sets of moderate sizes such as cc-pVDZ and aug-cc-pVDZ.
Range-separated double-hybrid density-functional theory applied to periodic systems
Energy Technology Data Exchange (ETDEWEB)
Sansone, Giuseppe; Civalleri, Bartolomeo; Maschio, Lorenzo, E-mail: lorenzo.maschio@unito.it [Dipartimento di Chimica and NIS (Nanostructured Interfaces and Surfaces) Centre, Università di Torino, via Giuria 5, I-10125 Torino (Italy); Usvyat, Denis [Institute for Physical and Theoretical Chemistry, Universität Regensburg, Universitätsstrasse 31, D-93040 Regensburg (Germany); Toulouse, Julien [Sorbonne Universités, UPMC Univ. Paris 06, UMR 7616, Laboratoire de Chimie Théorique, F-75005 Paris (France); CNRS, UMR 7616, Laboratoire de Chimie Théorique, F-75005 Paris (France); Sharkas, Kamal [Department of Chemistry, State University of New York at Buffalo, Buffalo, New York 14260-3000 (United States)
2015-09-14
Quantum chemistry methods exploiting density-functional approximations for short-range electron-electron interactions and second-order Møller-Plesset (MP2) perturbation theory for long-range electron-electron interactions have been implemented for periodic systems using Gaussian-type basis functions and the local correlation framework. The performance of these range-separated double hybrids has been benchmarked on a significant set of systems including rare-gas, molecular, ionic, and covalent crystals. The use of spin-component-scaled MP2 for the long-range part has been tested as well. The results show that the value of μ = 0.5 bohr{sup −1} for the range-separation parameter usually used for molecular systems is also a reasonable choice for solids. Overall, these range-separated double hybrids provide a good accuracy for binding energies using basis sets of moderate sizes such as cc-pVDZ and aug-cc-pVDZ.
High performance hybrid functional Petri net simulations of biological pathway models on CUDA.
Chalkidis, Georgios; Nagasaki, Masao; Miyano, Satoru
2011-01-01
Hybrid functional Petri nets are a wide-spread tool for representing and simulating biological models. Due to their potential of providing virtual drug testing environments, biological simulations have a growing impact on pharmaceutical research. Continuous research advancements in biology and medicine lead to exponentially increasing simulation times, thus raising the demand for performance accelerations by efficient and inexpensive parallel computation solutions. Recent developments in the field of general-purpose computation on graphics processing units (GPGPU) enabled the scientific community to port a variety of compute intensive algorithms onto the graphics processing unit (GPU). This work presents the first scheme for mapping biological hybrid functional Petri net models, which can handle both discrete and continuous entities, onto compute unified device architecture (CUDA) enabled GPUs. GPU accelerated simulations are observed to run up to 18 times faster than sequential implementations. Simulating the cell boundary formation by Delta-Notch signaling on a CUDA enabled GPU results in a speedup of approximately 7x for a model containing 1,600 cells.
A Hybrid PSO-BFGS Strategy for Global Optimization of Multimodal Functions.
Shutao Li; Mingkui Tan; Tsang, I W; Kwok, James Tin-Yau
2011-08-01
Particle swarm optimizer (PSO) is a powerful optimization algorithm that has been applied to a variety of problems. It can, however, suffer from premature convergence and slow convergence rate. Motivated by these two problems, a hybrid global optimization strategy combining PSOs with a modified Broyden-Fletcher-Goldfarb-Shanno (BFGS) method is presented in this paper. The modified BFGS method is integrated into the context of the PSOs to improve the particles' local search ability. In addition, in conjunction with the territory technique, a reposition technique to maintain the diversity of particles is proposed to improve the global search ability of PSOs. One advantage of the hybrid strategy is that it can effectively find multiple local solutions or global solutions to the multimodal functions in a box-constrained space. Based on these local solutions, a reconstruction technique can be adopted to further estimate better solutions. The proposed method is compared with several recently developed optimization algorithms on a set of 20 standard benchmark problems. Experimental results demonstrate that the proposed approach can obtain high-quality solutions on multimodal function optimization problems.
Rong, Yang; Bin, Tang; Tao, Gao; BingYun, Ao
2016-06-01
Hybrid density functional theory is employed to systematically investigate the structural, magnetic, vibrational, thermodynamic properties of plutonium monocarbide (PuC and PuC0.75). For comparison, the results obtained by DFT, DFT + U are also given. For PuC and PuC0.75, Fock-0.25 hybrid functional gives the best lattice constants and predicts the correct ground states of antiferromagnetic (AFM) structure. The calculated phonon spectra suggest that PuC and PuC0.75 are dynamically stable. Values of the Helmholtz free energy ΔF, internal energy ΔE, entropy S, and constant-volume specific heat C v of PuC and PuC0.75 are given. The results are in good agreement with available experimental or theoretical data. As for the chemical bonding nature, the difference charge densities, the partial densities of states and the Bader charge analysis suggest that the Pu-C bonds of PuC and PuC0.75 have a mixture of covalent character and ionic character. The effect of carbon vacancy on the chemical bonding is also discussed in detail. We expect that our study can provide some useful reference for further experimental research on the phonon density of states, thermodynamic properties of the plutonium monocarbide. Project supported by the National Natural Science Foundation of China (Grant Nos. 21371160 and 21401173).
Feasibility of a Hybrid Brain-Computer Interface for Advanced Functional Electrical Therapy
Directory of Open Access Journals (Sweden)
Andrej M. Savić
2014-01-01
Full Text Available We present a feasibility study of a novel hybrid brain-computer interface (BCI system for advanced functional electrical therapy (FET of grasp. FET procedure is improved with both automated stimulation pattern selection and stimulation triggering. The proposed hybrid BCI comprises the two BCI control signals: steady-state visual evoked potentials (SSVEP and event-related desynchronization (ERD. The sequence of the two stages, SSVEP-BCI and ERD-BCI, runs in a closed-loop architecture. The first stage, SSVEP-BCI, acts as a selector of electrical stimulation pattern that corresponds to one of the three basic types of grasp: palmar, lateral, or precision. In the second stage, ERD-BCI operates as a brain switch which activates the stimulation pattern selected in the previous stage. The system was tested in 6 healthy subjects who were all able to control the device with accuracy in a range of 0.64–0.96. The results provided the reference data needed for the planned clinical study. This novel BCI may promote further restoration of the impaired motor function by closing the loop between the “will to move” and contingent temporally synchronized sensory feedback.
Hybrid ultrasound and dual-wavelength optoacoustic biomicroscopy for functional neuroimaging
Rebling, Johannes; Estrada, Hector; Zwack, Michael; Sela, Gali; Gottschalk, Sven; Razansky, Daniel
2017-03-01
Many neurological disorders are linked to abnormal activation or pathological alterations of the vasculature in the affected brain region. Obtaining simultaneous morphological and physiological information of neurovasculature is very challenging due to the acoustic distortions and intense light scattering by the skull and brain. In addition, the size of cerebral vasculature in murine brains spans an extended range from just a few microns up to about a millimeter, all to be recorded in 3D and over an area of several dozens of mm2. Numerous imaging techniques exist that excel at characterizing certain aspects of this complex network but are only capable of providing information on a limited spatiotemporal scale. We present a hybrid ultrasound and dual-wavelength optoacoustic microscope, capable of rapid imaging of murine neurovasculature in-vivo, with high spatial resolution down to 12 μm over a large field of view exceeding 50mm2. The dual wavelength imaging capability allows for the visualization of functional blood parameters through an intact skull while pulse-echo ultrasound biomicroscopy images are captured simultaneously by the same scan head. The flexible hybrid design in combination with fast high-resolution imaging in 3D holds promise for generating better insights into the architecture and function of the neurovascular system.
Stochastic Optimally-Tuned Ranged-Separated Hybrid Density Functional Theory
Neuhauser, Daniel; Cytter, Yael; Baer, Roi
2015-01-01
We develop a stochastic formulation of the optimally-tuned range-separated hybrid density functional theory which enables significant reduction of the computational effort and scaling of the non-local exchange operator at the price of introducing a controllable statistical error. Our method is based on stochastic representations of the Coulomb convolution integral and of the generalized Kohn-Sham density matrix. The computational cost of the approach is similar to that of usual Kohn-Sham density functional theory, yet it provides much more accurate description of the quasiparticle energies for the frontier orbitals. This is illustrated for a series of silicon nanocrystals up to sizes exceeding 3000 electrons. Comparison with the stochastic GW many-body perturbation technique indicates excellent agreement for the fundamental band gap energies, good agreement for the band-edge quasiparticle excitations, and very low statistical errors in the total energy for large systems. The present approach has a major advan...
Li, Li
2016-01-01
© 2016 The Royal Society of Chemistry. The solubility behavior of Hf and Zr based hybrid nanoparticles with different surface ligands in different concentrations of photoacid generator as potential EUV photoresists was investigated in detail. The nanoparticles regardless of core or ligand chemistry have a hydrodynamic diameter of 2-3 nm and a very narrow size distribution in organic solvents. The Hansen solubility parameters for nanoparticles functionalized with IBA and 2MBA have the highest contribution from the dispersion interaction than those with tDMA and MAA, which show more polar character. The nanoparticles functionalized with unsaturated surface ligands showed more apparent solubility changes after exposure to DUV than those with saturated ones. The solubility differences after exposure are more pronounced for films containing a higher amount of photoacid generator. The work reported here provides material selection criteria and processing strategies for the design of high performance EUV photoresists.
Generation of novel functional metalloproteins via hybrids of cytochrome c and peroxidase.
Ying, Tianlei; Zhong, Fangfang; Wang, Zhong-Hua; Xie, Jin; Tan, Xiangshi; Huang, Zhong-Xian
2013-06-01
The continued interest in protein engineering has led to intense efforts in developing novel stable enzymes, which could not only give boost to industrial and biomedical applications, but also enhance our understanding of the structure-function relationships of proteins. We present here the generation of three hybrid proteins of cytochrome c (cyt c) and peroxidase via structure-based rational mutagenesis of cyt c. Several residues (positions 67, 70, 71 and 80) in the distal heme region of cyt c were mutated to the highly conserved amino acids in the heme pocket of peroxidases. The multiple mutants were found to exhibit high peroxidase activity and conserve the impressive stability of cyt c. We expect that this strategy could be extended to other cases of metalloprotein engineering, and lead to the development of stable and active biocatalysts for industrial uses. Besides, this study also provides insight into the structure-function relationships of hemoproteins.
A hybrid Evolutionary Functional Link Artificial Neural Network for Data mining and Classification
Directory of Open Access Journals (Sweden)
Faissal MILI
2012-08-01
Full Text Available This paper presents a specific structure of neural network as the functional link artificial neural network (FLANN. This technique has been employed for classification tasks of data mining. In fact, there are a few studies that used this tool for solving classification problems. In this present research, we propose a hybrid FLANN (HFLANN model, where the optimization process is performed using 3 known population based techniques such as genetic algorithms, particle swarm and differential evolution. This model will be empirically compared to FLANN based back-propagation algorithm and to others classifiers as decision tree, multilayer perceptron based back-propagation algorithm, radical basic function, support vector machine, and K-nearest Neighbor. Our results proved that the proposed model outperforms the other single model. (Abstract
Spin polarized HSE hybrid functional calculations of VO{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Schwingenschloegl, Udo; Wang, Hao [KAUST, PSE Division, Thuwal (Saudi Arabia); Grau-Crespo, Ricardo [University College London, London (United Kingdom)
2013-07-01
We study the rutile (R) and monoclinic (M1) phases of the prototypical compound VO{sub 2} by first principles calculations based on density functional theory, employing the Heyd-Scuseria-Ernzerhof (HSE) screened hybrid functional. Our results show that the HSE lowest-energy solutions for both the low-temperature M1 phase and the high-temperature R phase, which are obtained upon inclusion of spin polarization, are at odds with experimental observations. For the M1 phase the groundstate is (but should not be) magnetic, while the groundstate of the R phase, which is also spin-polarized, is not (but should be) metallic. The energy difference between the low-temperature and high-temperature phases is also in strong discrepancy with the experimental latent heat.
GalaxyDock BP2 score: a hybrid scoring function for accurate protein-ligand docking
Baek, Minkyung; Shin, Woong-Hee; Chung, Hwan Won; Seok, Chaok
2017-07-01
Protein-ligand docking is a useful tool for providing atomic-level understanding of protein functions in nature and design principles for artificial ligands or proteins with desired properties. The ability to identify the true binding pose of a ligand to a target protein among numerous possible candidate poses is an essential requirement for successful protein-ligand docking. Many previously developed docking scoring functions were trained to reproduce experimental binding affinities and were also used for scoring binding poses. However, in this study, we developed a new docking scoring function, called GalaxyDock BP2 Score, by directly training the scoring power of binding poses. This function is a hybrid of physics-based, empirical, and knowledge-based score terms that are balanced to strengthen the advantages of each component. The performance of the new scoring function exhibits significant improvement over existing scoring functions in decoy pose discrimination tests. In addition, when the score is used with the GalaxyDock2 protein-ligand docking program, it outperformed other state-of-the-art docking programs in docking tests on the Astex diverse set, the Cross2009 benchmark set, and the Astex non-native set. GalaxyDock BP2 Score and GalaxyDock2 with this score are freely available at http://galaxy.seoklab.org/softwares/galaxydock.html.
Li, Li; Chakrabarty, Souvik; Jiang, Jing; Zhang, Ben; Ober, Christopher; Giannelis, Emmanuel P.
2016-01-01
The solubility behavior of Hf and Zr based hybrid nanoparticles with different surface ligands in different concentrations of photoacid generator as potential EUV photoresists was investigated in detail. The nanoparticles regardless of core or ligand chemistry have a hydrodynamic diameter of 2-3 nm and a very narrow size distribution in organic solvents. The Hansen solubility parameters for nanoparticles functionalized with IBA and 2MBA have the highest contribution from the dispersion interaction than those with tDMA and MAA, which show more polar character. The nanoparticles functionalized with unsaturated surface ligands showed more apparent solubility changes after exposure to DUV than those with saturated ones. The solubility differences after exposure are more pronounced for films containing a higher amount of photoacid generator. The work reported here provides material selection criteria and processing strategies for the design of high performance EUV photoresists.The solubility behavior of Hf and Zr based hybrid nanoparticles with different surface ligands in different concentrations of photoacid generator as potential EUV photoresists was investigated in detail. The nanoparticles regardless of core or ligand chemistry have a hydrodynamic diameter of 2-3 nm and a very narrow size distribution in organic solvents. The Hansen solubility parameters for nanoparticles functionalized with IBA and 2MBA have the highest contribution from the dispersion interaction than those with tDMA and MAA, which show more polar character. The nanoparticles functionalized with unsaturated surface ligands showed more apparent solubility changes after exposure to DUV than those with saturated ones. The solubility differences after exposure are more pronounced for films containing a higher amount of photoacid generator. The work reported here provides material selection criteria and processing strategies for the design of high performance EUV photoresists. Electronic supplementary
Oosterhout, Stefan D.; Koster, L. Jan Anton; van Bavel, Svetlana S.; Loos, Joachim; Stenzel, Ole; Thiedmann, Ralf; Schmidt, Volker; Campo, Bert; Cleij, Thomas J.; Lutzen, Laurence; Vanderzande, Dirk; Wienk, Martijn M.; Janssen, Rene A. J.
2011-01-01
The efficiency of polymer - metal oxide hybrid solar cells depends critically on the intimacy of mixing of the two semiconductors. The effect of side chain functionalization on the morphology and performance of conjugated polymer:ZnO solar cells is investigated. Using an ester-functionalized side ch
Bjornsson, Ragnar; Bühl, Michael
2010-06-14
Electric field gradients (EFGs) were computed for the first-row transition metal nuclei in Cr(C(6)H(6))(CO)(3), MnO(3)F, Mn(CO)(5)H, MnCp(CO)(3), Co(CO)(4)H, Co(CO)(3)(NO) and VCp(CO)(4), for which experimental gas-phase data (in form of nuclear quadrupole coupling constants) are available from microwave spectroscopy. A variety of exchange-correlation functionals were assessed, among which range-separated hybrids (such as CAM-B3LYP or LC-omegaPBE) perform best, followed by global hybrids (such as B3LYP and PBE0) and gradient-corrected functionals (such as BP86). While large basis sets are required on the metal atom for converged EFGs, smaller basis sets can be employed on the ligands. In most cases, EFGs show little sensitivity toward the geometrical parameters.
The Hybrid Aesthetic Functional (HAF) Appliance: A Less Visible Proposal for Functional Orthodontics
2013-01-01
In modern orthodontics, aesthetics appear to have a decisive influence on orthodontic appliance preferences and acceptability. This paper reports the early application of a newly emerged functional device with enhanced aesthetics in a Class II treatment. Patient perspectives and technical considerations are discussed along with recommendations for further design development. It can be assumed that the use of thermoplastic material-based appliances may meet both the therapeutic and aesthetic demands of young age groups. PMID:23956884
Dong, Sheng; Hu, Zhicheng; Zhang, Kai; Yin, Qingwu; Jiang, Xiaofang; Huang, Fei; Cao, Yong
2017-06-20
A cross-linkable dual functional polymer hybrid electron transport layer (ETL) is developed by simply adding an amino-functionalized polymer dopant (PN4N) and a light crosslinker into a commercialized n-type semiconductor (N2200) matrix. It is found that the resulting hybrid ETL not only has a good solvent resistance, facilitating multilayers device fabrication but also exhibits much improved electron transporting/extraction properties due to the doping between PN4N and N2200. As a result, by using PTB7-Th:PC71 BM blend as an active layer, the inverted device based on the hybrid ETL can yield a prominent power conversion efficiency of around 10.07%. More interestingly, photovoltaic property studies of bilayer devices suggest that the absorption of the hybrid ETL contributes to photocurrent and hence the hybrid ETL simultaneously acts as both cathode interlayer material and an electron acceptor. The resulting inverted polymer solar cells function like a novel device architectures with a combination of a bulk heterojunction device and miniature bilayer devices. This work provides new insights on function of ETLs and may be open up a new direction for the design of new ETL materials and novel device architectures to further improve device performance. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Gil, Eun Seok; Park, Sang-Hyug; Tien, Lee W; Trimmer, Barry; Hudson, Samuel M; Kaplan, David L
2010-10-05
A route toward mechanically robust, rapidly actuating, and biologically functionalized polymeric actuators using macroporous soft materials is described. The materials were prepared by combining silk protein and a synthetic polymer (poly(N-isopropylacrylamide) (PNIAPPm)) to form interpenetrating network materials and macroporous structures by freeze-drying, with hundreds of micrometer diameter pores and exploiting the features of both polymers related to dynamic materials and structures. The chemically cross-linked PNIPAAm networks provided stimuli-responsive features, while the silk interpenetrating network formed by inducing protein β-sheet crystallinity in situ for physical cross-links provided material robustness, improved expansion force, and enzymatic degradability. The macroporous hybrid hydrogels showed enhanced thermal-responsive properties in comparison to pure PNIPAAm hydrogels, nonporous silk/PNIPAAm hybrid hydrogels, and previously reported macroporous PNIPAAm hydrogels. These new systems reach near equilibrium sizes in shrunken/swollen states in less than 1 min, with the structural features providing improved actuation rates and stable oscillatory properties due to the macroporous transport and the mechanically robust silk network. Confocal images of the hydrated hydrogels around the lower critical solution temperature (LCST) revealed macropores that could be used to track changes in the real time morphology upon thermal stimulus. The material system transformed from a macroporous to a nonporous structure upon enzymatic degradation. To extend the utility of the system, an affinity platform for a switchable or tunable system was developed by immobilizing biotin and avidin on the macropore surfaces.
Output Tracking Control of Switched Hybrid Systems: A Fliess Functional Expansion Approach
Directory of Open Access Journals (Sweden)
Fenghua He
2013-01-01
Full Text Available The output tracking problem is investigated for a nonlinear affine system with multiple modes of continuous control inputs. We convert the family of nonlinear affine systems under consideration into a switched hybrid system by introducing a multiple-valued logic variable. The Fliess functional expansion is adopted to express the input and output relationship of the switched hybrid system. The optimal switching control is determined for a multiple-step output tracking performance index. The proposed approach is applied to a multitarget tracking problem for a flight vehicle aiming for one real target with several decoys flying around it in the terminal guidance course. These decoys appear as apparent targets and have to be distinguished with the approaching of the flight vehicle. The guidance problem of one flight vehicle versus multiple apparent targets should be considered if no large miss distance might be caused due to the limitation of the flight vehicle maneuverability. The target orientation at each time interval is determined. Simulation results show the effectiveness of the proposed method.
Short- and long-range corrected hybrid density functionals with the D3 dispersion corrections
Wang, Chih-Wei; Chai, Jeng-Da
2016-01-01
We propose a short- and long-range corrected (SLC) hybrid scheme employing 100% Hartree-Fock (HF) exchange at both zero and infinite interelectronic distances, wherein three SLC hybrid density functionals with the D3 dispersion corrections (SLC-LDA-D3, SLC-PBE-D3, and SLC-B97-D3) are developed. SLC-PBE-D3 and SLC-B97-D3 are shown to be accurate for a very diverse range of applications, such as core ionization and excitation energies, thermochemistry, kinetics, noncovalent interactions, dissociation of symmetric radical cations, vertical ionization potentials, vertical electron affinities, fundamental gaps, and valence, Rydberg, and long-range charge-transfer excitation energies. Relative to omegaB97X-D, SLC-B97-D3 provides significant improvement for core ionization and excitation energies and noticeable improvement for the self-interaction, asymptote, energy-gap, and charge-transfer problems, while performing similarly for thermochemistry, kinetics, and noncovalent interactions.
A hybrid density functional view of native vacancies in gallium nitride.
Gillen, Roland; Robertson, John
2013-10-09
We investigated the transition energy levels of the vacancy defects in gallium nitride by means of a hybrid density functional theory approach (DFT). We show that, in contrast to predictions from a recent study on the level of purely local DFT, the inclusion of screened exchange stabilizes the triply positive charge state of the nitrogen vacancy for Fermi energies close to the valence band. On the other hand, the defect levels associated with the negative charge states of the nitrogen vacancy hybridize with the conduction band and turn out to be energetically unfavorable, except for high n-doping. For the gallium vacancy, the increased magnetic splitting between up-spin and down-spin bands due to stronger exchange interactions in sX-LDA pushes the defect levels deeper into the band gap and significantly increases the associated charge transition levels. Based on these results, we propose the ϵ(0| - 1) transition level as an alternative candidate for the yellow luminescence in GaN.
Probing the structure and function of biopolymer-carbon nanotube hybrids with molecular dynamics
Johnson, Robert R.
2009-12-01
active and function as a nanobiosensor with specific recognition of Knob proteins from the adenovirus capsid. Simulation also shows that the rigid CNT damps structural fluctuations in bound proteins, which may have important ramifications for biosensing devices composed of protein-CNT hybrids. These results expand current knowledge of Bio-CNT and demonstrate the effectiveness of MD for investigations of nanobiomolecular systems.
Fermi Surface Topology of Na0.5CoO2 from the Hybrid Density Functional
Institute of Scientific and Technical Information of China (English)
CHEN Zhao-Ying; XIANG Hong-Jun; YANG Jin-Long
2005-01-01
@@ The Fermi surface topology of Na0.5CoO2 is studied using the hybrid density functional theory. We first study a single (CoO2)0.5- layer model with the percentage of the nonlocal Hartree-Fock exchange changing from 0% to 20%. The results show that only when the mixed nonlocal Hartree-Fock exchange is between 1% and 5%, the Fermi surface topology is similar to the experimental one. With 3% HF exchange in the hybrid density functional,considering the effects of Na ions in the Na0.sCoO2 system, we find that the Fermi surface is split to double holes and small gaps open near the intersections between the Brillouin zone and the Fermi surface. Our results show that both the amounts of the nonlocal Hartree-Fock exchange in the hybrid density functional and the Na ions have much influence on the Fermi surface topology.
Diaconu, C V; Doll, J D; Freeman, D L; Diaconu, Cristian V.; Cho, Art E.; Freeman, David L.
2004-01-01
In the present work we investigate the adequacy of broken-symmetry (BS) unrestricted (U) density functional theory (DFT) for constructing the potential energy curve of nickel dimer and nickel hydride, as model for larger bare and hydrogenated nickel cluster calculations. We use three hybrid functionals: B3LYP, Becke98, and FSLYP (50% Hartree-Fock and 50% Slater exchange and LYP correlation functional) with two basis sets: all-electron (AE) Wachters+f basis set and Stuttgart RSC effective core potential (ECP) and basis set. We find that, overall, B3LYP functional with Wachters+f AE basis set performs best, with only 1.3% root-mean-square (RMS) deviation from experiment, followed by Becke98/AE and B3LYP/ECP, with RMS deviation from experimental value of 2.5% and 2.7%, respectively. We also find that for Ni dimer, the spin-projection for the broken-symmetry unrestricted singlet states changes the ordering of the states, but the splittings are less than 10 meV. All our calculations predict a (delta)(delta)-hole g...
Preparation and toxicological assessment of functionalized carbon nanotube-polymer hybrids.
Directory of Open Access Journals (Sweden)
Nikos D Koromilas
Full Text Available Novel Carbon Nanotube-Polymer Hybrids were synthesized as potential materials for the development of membranes for water treatment applications in the field of Membrane Bioreactors (MBRs. Due to the toxicological concerns regarding the use of nanomaterials in water treatment as well as the rising demand for safe drinking water to protect public health, we studied the functionalization of MWCNTs and Thin-MWCNTs as to control their properties and increase their ability of embedment into porous anisotropic polymeric membranes. Following the growth of the hydrophilic monomer on the surface of the properly functionalized CNTs, that act as initiator for the controlled radical polymerization (ATRP of sodium styrene sulfonate (SSNa, the antimicrobial quaternized phosphonium and ammonium salts were attached on CNTs-g-PSSNa through non-covalent bonding. In another approach the covalent attachment of quaternized ammonium polymeric moieties of acrylic acid-vinyl benzyl chloride copolymers with N,N-dimethylhexadecylamine (P(AA12-co-VBCHAM on functionalized CNTs has also been attempted. Finally, the toxicological assessment in terms of cell viability and cell morphological changes revealed that surface characteristics play a major role in the biological response of functionalized CNTs.
Density functional theory in quantum chemistry
Tsuneda, Takao
2014-01-01
This book examines density functional theory based on the foundation of quantum chemistry. Unconventional in approach, it reviews basic concepts, then describes the physical meanings of state-of-the-art exchange-correlation functionals and their corrections.
Diffusion of interstitial oxygen in silicon and germanium: a hybrid functional study
Colleoni, Davide; Pasquarello, Alfredo
2016-12-01
The minimum-energy paths for the diffusion of an interstitial O atom in silicon and germanium are studied through the nudged-elastic-band method and hybrid functional calculations. The reconsideration of the diffusion of O in silicon primarily serves the purpose of validating the procedure for studying the O diffusion in germanium. Our calculations show that the minimum energy path goes through an asymmetric transition state in both silicon and germanium. The stability of these transition states is found to be enhanced by the generation of unpaired electrons in the highest occupied single-particle states. Calculated energy barriers are 2.54 and 2.14 eV for Si and Ge, in very good agreement with corresponding experimental values of 2.53 and 2.08 eV, respectively.
A hybrid density functional study on the electron and hole trap states in anatase titanium dioxide.
Yamamoto, Takenori; Ohno, Takahisa
2012-01-14
We present a theoretical study on electron and hole trap states in the bulk and (001) surface of anatase titanium dioxide using screened hybrid density functional calculations. In both the bulk and surface, calculations suggest that the neutral and ionized oxygen vacancies are possible electron traps. The doubly ionized oxygen vacancy is the most stable in the bulk, and is a candidate for a shallow donor in colorless anatase crystals. The hole trap states are localized at oxygen anions in both the bulk and surface. The self-trapped electron centered at a titanium cation cannot be produced in the bulk, but can be formed at the surface. The electron trap level at the surface oxygen vacancy is consistent with observations by photoelectron spectroscopy. The optical absorptions and luminescence in UV-irradiated anatase nanoparticles are found to come from the surface self-trapped hole and the surface oxygen vacancy.
Oxygen defects in amorphous Al{sub 2}O{sub 3}: A hybrid functional study
Energy Technology Data Exchange (ETDEWEB)
Guo, Zhendong, E-mail: zhendong.guo@epfl.ch; Ambrosio, Francesco; Pasquarello, Alfredo [Chaire de Simulation à l' Echelle Atomique (CSEA), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)
2016-08-08
The electronic properties of the oxygen vacancy and interstitial in amorphous Al{sub 2}O{sub 3} are studied via ab initio molecular dynamics simulations and hybrid functional calculations. Our results indicate that these defects do not occur in amorphous Al{sub 2}O{sub 3}, due to structural rearrangements which assimilate the defect structure and cause a delocalization of the associated defect levels. The imbalance of oxygen leads to a nonstoichiometric compound in which the oxygen occurs in the form of O{sup 2–} ions. Intrinsic oxygen defects are found to be unable to trap excess electrons. For low Fermi energies, the formation of peroxy linkages is found to be favored leading to the capture of holes. The relative +2/0 defect levels occur at 2.5 eV from the valence band.
Directory of Open Access Journals (Sweden)
Li Mao
2016-01-01
Full Text Available Artificial bee colony (ABC algorithm has good performance in discovering the optimal solutions to difficult optimization problems, but it has weak local search ability and easily plunges into local optimum. In this paper, we introduce the chemotactic behavior of Bacterial Foraging Optimization into employed bees and adopt the principle of moving the particles toward the best solutions in the particle swarm optimization to improve the global search ability of onlooker bees and gain a hybrid artificial bee colony (HABC algorithm. To obtain a global optimal solution efficiently, we make HABC algorithm converge rapidly in the early stages of the search process, and the search range contracts dynamically during the late stages. Our experimental results on 16 benchmark functions of CEC 2014 show that HABC achieves significant improvement at accuracy and convergence rate, compared with the standard ABC, best-so-far ABC, directed ABC, Gaussian ABC, improved ABC, and memetic ABC algorithms.
Why the Heyd-Scuseria-Ernzerhof hybrid functional description of VO2 phases is not correct
Grau-Crespo, Ricardo
2012-08-06
In contrast with recent claims that the Heyd-Scuseria-Ernzerhof (HSE) screened hybrid functional can provide a good description of the electronic and magnetic structures of VO2 phases, we show here that the HSE lowest-energy solutions for both the low-temperature monoclinic (M1) phase and the high-temperature rutile (R) phase, which are obtained upon inclusion of spin polarization, are at odds with experimental observations. For the M1 phase the ground state is (but should not be) magnetic, while the ground state of the R phase, which is also spin polarized, is not (but should be) metallic. The energy difference between the low-temperature and high-temperature phases has strong discrepancies with the experimental latent heat.
Implementation of Special Function Unit for Vertex Shader Processor Using Hybrid Number System
Directory of Open Access Journals (Sweden)
Avni Agarwal
2014-01-01
Full Text Available The world of 3D graphic computing has undergone a revolution in the recent past, making devices more computationally intensive, providing high-end imaging to the user. The OpenGL ES Standard documents the requirements of graphic processing unit. A prime feature of this standard is a special function unit (SFU, which performs all the required mathematical computations on the vertex information corresponding to the image. This paper presents a low-cost, high-performance SFU architecture with improved speed and reduced area. Hybrid number system is employed here in order to reduce the complexity of operations by suitably switching between logarithmic number system (LNS and binary number system (BNS. In this work, reduction of area and a higher operating frequency are achieved with almost the same power consumption as that of the existing implementations.
Doping strategies to control A-centres in silicon: Insights from hybrid density functional theory
Wang, Hao
2014-01-01
Hybrid density functional theory is used to gain insights into the interaction of intrinsic vacancies (V) and oxygen-vacancy pairs (VO, known as A-centres) with the dopants (D) germanium (Ge), tin (Sn), and lead (Pb) in silicon (Si). We determine the structures as well as binding and formation energies of the DVO and DV complexes. The results are discussed in terms of the density of states and in view of the potential of isovalent doping to control A-centres in Si. We argue that doping with Sn is the most efficient isovalent doping strategy to suppress A-centres by the formation of SnVO complexes, as these are charge neutral and strongly bound. © 2014 the Owner Societies.
G-centers in irradiated silicon revisited: A screened hybrid density functional theory approach
Energy Technology Data Exchange (ETDEWEB)
Wang, H.; Schwingenschlögl, U., E-mail: Udo.Schwingenschlogl@kaust.edu.sa [PSE Division, KAUST, Thuwal 23955-6900 (Saudi Arabia); Chroneos, A., E-mail: Alex.Chroneos@open.ac.uk [Engineering and Innovation, The Open University, Milton Keynes MK7 6AA (United Kingdom); Department of Materials, Imperial College, London SW7 2AZ (United Kingdom); Londos, C. A.; Sgourou, E. N. [University of Athens, Solid State Physics Section, Panepistimiopolis Zografos, Athens 157 84 (Greece)
2014-05-14
Electronic structure calculations employing screened hybrid density functional theory are used to gain fundamental insight into the interaction of carbon interstitial (C{sub i}) and substitutional (C{sub s}) atoms forming the C{sub i}C{sub s} defect known as G-center in silicon (Si). The G-center is one of the most important radiation related defects in Czochralski grown Si. We systematically investigate the density of states and formation energy for different types of C{sub i}C{sub s} defects with respect to the Fermi energy for all possible charge states. Prevalence of the neutral state for the C-type defect is established.
Zeng, Xiang-Yang; Wang, Shu-Guang; Gao, Li-Ping
2010-09-01
As the basic data for virtual auditory technology, head-related transfer function (HRTF) has many applications in the areas of room acoustic modeling, spatial hearing and multimedia. How to individualize HRTF fast and effectively has become an opening problem at present. Based on the similarity and relativity of anthropometric structures, a hybrid HRTF customization algorithm, which has combined the method of principal component analysis (PCA), multiple linear regression (MLR) and database matching (DM), has been presented in this paper. The HRTFs selected by both the best match and the worst match have been applied into obtaining binaurally auralized sounds, which are then used for subjective listening experiments and the results are compared. For the area in the horizontal plane, the localization results have shown that the selection of HRTFs can enhance the localization accuracy and can also abate the problem of front-back confusion.
He, Jiangang; Franchini, Cesare
2017-08-16
In this paper we assess the predictive power of the self-consistent hybrid functional scPBE0 in calculating the band gap of oxide semiconductors. The computational procedure is based on the self-consistent evaluation of the mixing parameter α by means of an iterative calculation of the static dielectric constant using the perturbation expansion after discretization (PEAD) method and making use of the relation α = 1/ε_{∞}. Our materials dataset is formed by 30 compounds covering a wide range of band gaps and dielectric properties, and includes materials with a wide spectrum of application as thermoelectrics, photocatalysis, photovoltaics, transparent conducting oxides, and refractory materials. Our results show that the scPBE0 functional provides better band gaps than the non self-consistent hybrids PBE0 and HSE06, but scPBE0 does not show significant improvement on the description of the static dielectric constants. Overall, the scPBE0 data exhibit a mean absolute percentage error of 14 % (band gaps) and 10 % (α = 1/ε_{∞}). For materials with weak dielectric screening and large excitonic biding energies scPBE0, unlike PBE0 and HSE06, overestimates the band gaps, but the value of the gap become very close to the experimental value when excitonic effects are included (e.g. for SiO_{2}). However, special caution must be given to the compounds with small band gaps due to the tendency of scPBE0 to overestimate the dielectric constant in proximity of the metallic limit. © 2017 IOP Publishing Ltd.
Linear-response thermal time-dependent density functional theory
Pribram-Jones, Aurora; Burke, Kieron
2015-01-01
The van Leeuwen proof of linear-response time-dependent density functional theory (TDDFT) is generalized to thermal ensembles. This allows generalization to finite temperatures of the Gross-Kohn relation, the exchange-correlation kernel of TDDFT, and fluctuation dissipation theorem for DFT. This produces a natural method for generating new thermal exchange-correlation (XC) approximations.
Energy Technology Data Exchange (ETDEWEB)
Luca, V. [Programa Nacional de Gestion de Residuos Radiactivos, Comision Nacional de Energia Atomica, Centro Atomico Constituyentes, Av. General, Paz 1499, 1650 San Martin, Provincia de Buenos Aires (Argentina)
2013-07-01
Functionalized meso-porous materials are a class of hybrid organic-inorganic material in which a meso-porous metal oxide framework is functionalized with multifunctional organic molecules. These molecules may contain one or more anchor groups that form strong bonds to the pore surfaces of the metal oxide framework and free functional groups that can impart and or modify the functionality of the material such as for binding metal ions in solution. Such materials have been extensively studied over the past decade and are of particular interest in absorption applications because of the tremendous versatility in choosing the composition and architecture of the metal oxide framework and the nature of the functional organic molecule as well as the efficient mass transfer that can occur through a well-designed hierarchically porous network. A sorbent for nuclear applications would have to be highly selective for particular radio nuclides, it would need to be hydrolytically and radiolytically stable, and it would have to possess reasonable capacity and fast kinetics. The sorbent would also have to be available in a form suitable for use in a column. Finally, it would also be desirable if once saturated with radio nuclides, the sorbent could be recycled or converted directly into a ceramic or glass waste form suitable for direct repository disposal or even converted directly into a material that could be used as a transmutation target. Such a cradle-to- grave strategy could have many benefits in so far as process efficiency and the generation of secondary wastes are concerned.This paper will provide an overview of work done on all of the above mentioned aspects of the development of functionalized meso-porous adsorbent materials for the selective separation of lanthanides and actinides and discuss the prospects for future implementation of a cradle-to-grave strategy with such materials. (author)
Cao, Li; Kong, Lei; Kong, Lingqian; Zhang, Xingxiang; Shi, Haifeng
2015-12-01
Hybrid membranes (SPI/ZGO) composed of sulfonated polyimide (SPI) and zwitterionic polymer-functionalized graphene oxide (ZGO) are fabricated via a solution-casting method for vanadium redox flow battery (VRB). Successful preparation of ZGO fillers and SPI/ZGO hybrid membranes are demonstrated by FT-IR, XPS and SEM, indicating that ZGO fillers is homogeneously dispersed into SPI matrix. Through controlling the interfacial interaction between SPI matrix and ZGO fillers, the physicochemical properties, e.g., vanadium ion barrier and proton transport pathway, of hybrid membranes are tuned via the zwitterionic acid-base interaction in the hybrid membrane, showing a high ion selectivity and good stability with the incorporated ZGO fillers. SPI/ZGO-4 hybrid membrane proves a higher cell efficiencies (CE: 92-98%, EE: 65-79%) than commercial Nafion 117 membrane (CE: 89-94%, EE: 59-70%) for VRB application at 30-80 mA cm-2. The assembled VRB with SPI/ZGO-4 membrane presents a stable cycling charge-discharge performance over 280 times, which demonstrates its excellent chemical stability under the strong acidic and oxidizing conditions. SPI/ZGO hybrid membranes show a brilliant perspective for VRB application.
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.
Hybrid functional study rationalizes the simple cubic phase of calcium at high pressures.
Liu, Hanyu; Cui, Wenwen; Ma, Yanming
2012-11-14
Simple cubic (SC) phase has been long experimentally determined as the high-pressure phase III of elemental calcium (Ca) since 1984. However, recent density functional calculations within semi-local approximation showed that this SC phase is structurally unstable by exhibiting severely imaginary phonons, and is energetically unstable with respect to a theoretical body-centered tetragonal I4(1)/amd structure over the pressure range of phase III. These calculations generated extensive debates on the validity of SC phase. Here we have re-examined the SC structure by performing more precise density functional calculations within hybrid functionals of Heyd-Scuseria-Erhzerhof and PBE0. Our calculations were able to rationalize fundamentally the phase stability of SC structure over all other known phases by evidence of its actual energetic stability above 33 GPa and its intrinsically dynamical stability without showing any imaginary phonons in the entire pressure range studied. We further established that the long-thought theoretical I4(1)/amd structure remains stable in a narrow pressure range before entering SC phase and is actually the structure of experimental Ca-III(') synthesized recently at low temperature 14 K as supported by the excellent agreement between our simulated x-ray diffraction patterns and the experimental data. Our results shed strong light on the crucial role played by the precise electron exchange energy in a proper description of the potential energy of Ca.
Functionalization of hybrid monolithic columns via thiol-ene click reaction for proteomics analysis.
Liu, Zhongshan; Liu, Jing; Liu, Zheyi; Wang, Hongwei; Ou, Junjie; Ye, Mingliang; Zou, Hanfa
2017-05-19
The vinyl-functionalized hybrid monolithic columns (75 and 150μm i.d.) were prepared via sol-gel chemistry of tetramethoxysilane (TMOS) and vinyltrimethoxysilane (VTMS). The content of accessible vinyl groups was further improved after the monolithic column was post-treated with vinyldimethylethoxysilane (VDMES). The surface properties of monolithic columns were tailored via thiol-ene click reaction by using 1-octadecanethiol, sodium 3-mercapto-1-propanesulfonate and 2,2'-(ethylenedioxy)diethanethiol/vinylphosphonic acid, respectively. The preparing octadecyl-functionalized monolithic columns were adopted for proteomics analysis in cLC-MS/MS. A 37-cm-long×75-μm-i.d. monolithic column could identify 3918 unique peptides and 1067 unique proteins in the tryptic digest of proteins from HeLa cells. When a 90-cm-long×75-μm-i.d. monolithic column was used, the numbers of unique peptides and proteins were increased by 82% and 32%, respectively. Furthermore, strong cation exchange (SCX) monolithic columns (4cm in length×150μm i.d.) were also prepared and coupled with the 37-cm-long×75-μm-i.d. octadecyl-functionalized monolithic column for two-dimensional SCX-RPLC-MS/MS analysis, which could identify 17114 unique peptides and 3211 unique proteins. Copyright © 2017 Elsevier B.V. All rights reserved.
Zhong, Chang; Zhao, Min; Goslinski, Tomasz; Stern, Charlotte; Barrett, Anthony G M; Hoffman, Brian M
2006-05-15
We report the synthesis and physical characterization of a new family of peripherally functionalized porphyrazine (pz) compounds, denoted 1[M1, M2], where metal ion M1 is incorporated into the pz core and metal ion M2 is bound to a salicylidene/picolinamide "hybrid" chelate built onto two nitrogen atoms attached to the pz periphery. The complexes 1[MnCl, Cu], 1[VO, Cu], and 1[Cu, Cu] have been prepared, and crystal structures show 1[MnCl, Cu] and 1[VO, Cu] to be isostructural. These complexes have been subjected to electron paramagnetic resonance and temperature-dependent magnetic susceptibility measurements. The variation of the ligand-mediated exchange splittings (delta) in these complexes is striking: delta/k(B) values for 1[MnCl, Cu] and 1[VO, Cu] are 22 and 40 K, respectively, while delta/k(B) for 1[Cu, Cu] is only 1 K. These coupling results are explained in terms of the relative orientation of the M1 and M2 orbitals and reflect the fact that the ligand set of M2 in the periphery is rotated in-plane by 45 degrees relative to the effectively coplanar pz ligand set of M1. The exchange couplings are essentially the same as those we determined for the Schiff base porphyrazines (pzs). Thus, the hybrid ligand has eliminated the dimerization found to occur when Cu(II) is bound to the periphery of bis(picolinamido) pzs and has created a more robust ligand system than the Schiff base pzs while retaining the ability they show to promote spin coupling between M1 and M2.
Energy Technology Data Exchange (ETDEWEB)
Gritsenko, O.V.; Schipper, P.R.T.; Baerends, E.J.
2000-01-20
The long-range asymptotic behavior of the exchange-correlation Kohn-Sham (KS) potential {nu}{sub xc} and its relation to the exchange-correlation energy E{sub xc} are considered using various approaches. The line integral of {nu}{sub xc}([{rho}];r) yielding the exchange-correlation part {Delta}E{sub xc} of a relative energy {Delta}E of a finite system, shows that a uniform constant shift of {nu}{sub xc} never shows up in any physically meaningful energy difference {Delta}E. {nu}{sub xv} may thus be freely chosen to tend asymptotically to zero or to some nonzero constant. Possible choices of the asymptotics of the potential are discussed with reference to the theory of open systems with a fractional number of electrons. The authors adhere to the conventional choice {nu}{sub xc}({infinity}) = 0 for the asymptotics of the potential leading to {epsilon}{sub N} = {minus}I{sub p} for the energy {epsilon}{sub N} of the highest occupied orbital. A statistical average of orbital dependent model potentials is proposed as a way to model {nu}{sub xc}. An approximate potential {nu}{sub xco}{sup SAOP} with exact {minus}1/r asymptotics is developed using the statistical average of, on the one hand, a model potential {nu}{sub xc{sigma}}{sup Ei} for the highest occupied KS orbital {psi}{sub N{sigma}} and, on the other hand, a model potential {nu}{sub xc}{sup GLB} for other occupied orbitals. It is demonstrated for the well-studied case of the Ne atom, that calculations with the new model potential can, in principle, reproduce perfectly all energy characteristics.
Rohm, Martin; Schneiders, Matthias; Müller, Constantin; Kreilinger, Alex; Kaiser, Vera; Müller-Putz, Gernot R; Rupp, Rüdiger
2013-10-01
The bilateral loss of the grasp function associated with a lesion of the cervical spinal cord severely limits the affected individuals' ability to live independently and return to gainful employment after sustaining a spinal cord injury (SCI). Any improvement in lost or limited grasp function is highly desirable. With current neuroprostheses, relevant improvements can be achieved in end users with preserved shoulder and elbow, but missing hand function. The aim of this single case study is to show that (1) with the support of hybrid neuroprostheses combining functional electrical stimulation (FES) with orthoses, restoration of hand, finger and elbow function is possible in users with high-level SCI and (2) shared control principles can be effectively used to allow for a brain-computer interface (BCI) control, even if only moderate BCI performance is achieved after extensive training. The individual in this study is a right-handed 41-year-old man who sustained a traumatic SCI in 2009 and has a complete motor and sensory lesion at the level of C4. He is unable to generate functionally relevant movements of the elbow, hand and fingers on either side. He underwent extensive FES training (30-45min, 2-3 times per week for 6 months) and motor imagery (MI) BCI training (415 runs in 43 sessions over 12 months). To meet individual needs, the system was designed in a modular fashion including an intelligent control approach encompassing two input modalities, namely an MI-BCI and shoulder movements. After one year of training, the end user's MI-BCI performance ranged from 50% to 93% (average: 70.5%). The performance of the hybrid system was evaluated with different functional assessments. The user was able to transfer objects of the grasp-and-release-test and he succeeded in eating a pretzel stick, signing a document and eating an ice cream cone, which he was unable to do without the system. This proof-of-concept study has demonstrated that with the support of hybrid FES
Brorsen, Kurt R; Yang, Yang; Pak, Michael V; Hammes-Schiffer, Sharon
2017-05-04
The development of approximate exchange-correlation functionals is critical for modern density functional theory. A recent analysis of atomic systems suggested that some modern functionals are straying from the path toward the exact functional because electron densities are becoming less accurate while energies are becoming more accurate since the year 2000. To investigate this trend for more chemically relevant systems, the electron densities in the bonding regions and the atomization energies are analyzed for a series of diatomic molecules with 90 different functionals. For hybrid generalized gradient approximation functionals developed since the year 2000, the errors in densities and atomization energies are decoupled; the accuracy of the energies remains relatively consistent while the accuracy of the densities varies significantly. Such decoupling is not observed for generalized gradient and meta-generalized gradient approximation functionals. Analysis of electron densities in bonding regions is found to be important for the evaluation of functionals for chemical systems.
Xu, Ting; Zhao, Xin; Zhang, Junxian; Dong, Jie; Zhang, Qinghua
2016-04-01
Two kinds of ternary hybrids were prepared by anchoring different shapes and loadings of Au nanoparticles (NPs) on poly(dopamine) (PDA) functionalized polystyrene (PS) microspheres with two different strategies, i.e., in situ reduction and self-assembly approach. PDA coatings were firstly introduced to functionalize the hydrophobic PS surface with sufficient amino and hydroxyl groups, which enhanced the interaction between Au NPs and the polymer spheres. Thus, Au NPs could be easily immobilized onto the surface of the PDA/PS microspheres, and the hierarchical composite microspheres exhibited a well-defined core/shell structure without sacrificing the spherical PS morphology. PS/PDA/Au-R and PS/PDA/Au-A microspheres fabricated by in situ reduction and self-assembly approach showed different distinct Au nano-shell morphology with the corresponding optical, catalytic and electrochemical properties. Field emission scanning electron microscopy and transmission electronic microscopy verified these hierarchical structures with the ultrathin PDA film incorporating between the inner PS core and the outer Au NPs shell. X-ray diffraction and X-ray photoelectron spectroscopy confirmed the presence of PDA and Au layer on the surface of the composite particles. These green and facile methods with mild experimental conditions can extend to fabricate other polymer or inorganic substrates coated by various noble metals.
Functionalized hybrid nanofibers to mimic native ECM for tissue engineering applications
Karuppuswamy, Priyadharsini; Venugopal, Jayarama Reddy; Navaneethan, Balchandar; Laiva, Ashang Luwang; Sridhar, Sreepathy; Ramakrishna, Seeram
2014-12-01
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 tissue engineering applications.
Properties of carbon impurities in ZnO: A hybrid functional study
Li, Ping; Luo, Weidong
2016-08-01
The mechanism of the room temperature (RT) ferromagnetism in C-doped ZnO and the trend that the higher the C concentration, the smaller the saturation magnetic moment (Ms), have remained controversial and puzzling for a long time. Using density-functional calculations with hybrid functional, we qualitatively understand these experimental phenomena. The substitutional CO defects dominate in Zn-rich conditions and n -type materials. They carry 1 or 2 μB/C , depending on the position of the Fermi level. In low C concentrations and at RT, the CO defects are kept isolated and prefer to couple ferromagnetically, thus the Ms is larger. As the C concentration increases, nonmagnetic C2 dimers form through binding of two CO defects or binding of one CO defect with one interstitial C, thus decreasing the Ms. Our results also suggest that the ferromagnetism from CO defects can be quenched by higher annealing temperatures. Furthermore, the p -type conductivity from carbon dopant is not supported in the present study.
Ab-initio study of germanium di-interstitial using a hybrid functional (HSE)
Igumbor, E.; Ouma, C. N. M.; Webb, G.; Meyer, W. E.
2016-01-01
In this work, we present ab-initio calculation results of Ge di-interstitials (I2(Ge)) in the framework of the density functional theory (DFT) using the Heyd, Scuseria, and Ernzerhof (HSE) hybrid functional. The formation energy, transition levels and minimum energy configurations were obtained for I2(Ge) -2, -1, 0, +1 and +2 charge states. The calculated formation energies show that for all charge states of I2(Ge), the double tetrahedral (T) configuration formed the most stable defect with a binding energy of 1.24 eV in the neutral state. We found the (+2/+1) charge state transition level for the T lying below the conduction band minimum and (+2/+1) for the split[110]-tetrahedral configuration lying deep at 0.41 eV above the valence band maximum. The di-interstitials in Ge exhibited the properties of both shallow and deep donor levels at (+2/+1) within the band gap and depending on the configurations. I2(Ge) gave rise to negative-U, with effective-U values of -0.61 and -1.6 eV in different configurations. We have compared our results with calculations of di-interstitials in silicon and available experimental data.
Rare Earth Interstitials in Ge: A Hybrid Density Functional Theory Study
Igumbor, E.; Andrew, R. C.; Meyer, W. E.
2017-02-01
In this work, the results of density functional theory calculations for rare earth (Ce, Pr, Eu, and Er) interstitials in Ge are presented. We employed the hybrid functional of Heyd, Scuseria, and Ernzerhof (HSE06) for all the calculations. We calculated the formation energies and charge state transition levels for the tetrahedral (T) and hexagonal (H) configurations of the Ce, Pr, Eu, and Er interstitials in Ge. While for the T configuration, the charge states of the Ce and Pr did not induce any thermodynamic accessible transition state level within the band gap of Ge, for both the T and H configurations the Eu and Er interstitials in Ge induce deep levels in the band gap. The H configuration of the Ce interstitial in Ge induces a shallow donor level at 0.03 eV below the conduction band. The Eu interstitial exhibits negative-U properties for the (+2/-2) transition level and the Er interstitial displays characteristics of charge state controlled metastability.
Covercrete with hybrid functions - A novel approach to durable reinforced concrete structures
Energy Technology Data Exchange (ETDEWEB)
Tang, L.; Zhang, E.Q. [Chalmers University of Technology, SE-412 96 Gothenburg (Sweden); Fu, Y. [KTH Royal Institute of Technology, SE-106 91 Stockholm (Sweden); Schouenborg, B.; Lindqvist, J.E. [CBI Swedish Cement and Concrete Research Institute, c/o SP, Box 857, SE-501 15 Boraas (Sweden)
2012-12-15
Due to the corrosion of steel in reinforced concrete structures, the concrete with low water-cement ratio (w/c), high cement content, and large cover thickness is conventionally used for prolonging the passivation period of steel. Obviously, this conventional approach to durable concrete structures is at the sacrifice of more CO{sub 2} emission and natural resources through consuming higher amount of cement and more constituent materials, which is against sustainability. By placing an economically affordable conductive mesh made of carbon fiber or conductive polymer fiber in the near surface zone of concrete acting as anode we can build up a cathodic prevention system with intermittent low current density supplied by, e.g., the solar cells. In such a way, the aggressive negative ions such as Cl{sup -}, CO{sub 3}{sup 2-}, and SO{sub 4}{sup 2-} can be stopped near the cathodic (steel) zone. Thus the reinforcement steel is prevented from corrosion even in the concrete with relatively high w/c and small cover thickness. This conductive mesh functions not only as electrode, but also as surface reinforcement to prevent concrete surface from cracking. Therefore, this new type of covercrete has hybrid functions. This paper presents the theoretical analysis of feasibility of this approach and discusses the potential durability problems and possible solutions to the potential problems. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Ab‐initio study of germanium di-interstitial using a hybrid functional (HSE)
Energy Technology Data Exchange (ETDEWEB)
Igumbor, E., E-mail: elgumuk@gmail.com [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa); Department of Mathematics and Physical Sciences, Samuel Adegboyega University, Km 1 Ogwa/Ehor Rd, Ogwa, Edo State (Nigeria); Ouma, C.N.M.; Webb, G. [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa); Meyer, W.E., E-mail: wmeyer@up.ac.za [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa)
2016-01-01
In this work, we present ab‐initio calculation results of Ge di-interstitials (I{sub 2(Ge)}) in the framework of the density functional theory (DFT) using the Heyd, Scuseria, and Ernzerhof (HSE) hybrid functional. The formation energy, transition levels and minimum energy configurations were obtained for I{sub 2(Ge)} −2, −1, 0, +1 and +2 charge states. The calculated formation energies show that for all charge states of I{sub 2(Ge)}, the double tetrahedral (T) configuration formed the most stable defect with a binding energy of 1.24 eV in the neutral state. We found the (+2/+1) charge state transition level for the T lying below the conduction band minimum and (+2/+1) for the split[110]-tetrahedral configuration lying deep at 0.41 eV above the valence band maximum. The di-interstitials in Ge exhibited the properties of both shallow and deep donor levels at (+2/+1) within the band gap and depending on the configurations. I{sub 2(Ge)} gave rise to negative-U, with effective-U values of −0.61 and −1.6 eV in different configurations. We have compared our results with calculations of di-interstitials in silicon and available experimental data.
Functionalized Self-Assembled InAs/GaAs Quantum-Dot Structures Hybridized with Organic Molecules
DEFF Research Database (Denmark)
Chen, Miaoxiang Max; Kobashi, K.; Chen, B.
2010-01-01
Low-dimensional III-V semiconductors have many advantages over other semiconductors; however, they are not particularly stable under physiological conditions. Hybridizing biocompatible organic molecules with advanced optical and electronic semiconductor devices based on quantum dots (QDs......) and quantum wires could provide an efficient solution to realize stress-free and nontoxic interfaces to attach larger functional biomolecules. Monitoring the modifications of the optical properties of the hybrid molecule-QD systems by grafting various types of air-stable diazonium salts onto the QD structures...
Energy Technology Data Exchange (ETDEWEB)
Na, Moonkyong, E-mail: nmk@keri.re.kr [HVDC Research Division, Korea Electrotechnology Research Institute, Changwon, 642-120 (Korea, Republic of); System on Chip Chemical Process Research Center, Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 790-784 (Korea, Republic of); Kang, Young Taec [Creative and Fundamental Research Division, Korea Electrotechnology Research Institute, Changwon, 642-120 (Korea, Republic of); Department of Polymer Science and Engineering, Pusan National University, Busan, 609-735 (Korea, Republic of); Kim, Sang Cheol [HVDC Research Division, Korea Electrotechnology Research Institute, Changwon, 642-120 (Korea, Republic of); Kim, Eun Dong [Creative and Fundamental Research Division, Korea Electrotechnology Research Institute, Changwon, 642-120 (Korea, Republic of)
2013-07-31
Thermal-cured hybrid materials were synthesized from homogenous hybrid sols of epoxy resins and organoalkoxysilane-functionalized silica. The chemical structures of raw materials and obtained hybrid materials were characterized using Fourier transform infrared spectroscopy. The thermal resistance of the hybrids was enhanced by hybridization. The interaction between epoxy matrix and the silica particles, which caused hydrogen bonding and van der Waals force was strengthened by organoalkoxysilane. The degradation temperature of the hybrids was improved by approximately 30 °C over that of the parent epoxy material. The hybrid materials were formed into uniformly coated thin films of about 50 nm-thick using a spin coater. An optimum mixing ratio was used to form smooth-surfaced hybrid films. The electrical property of the hybrid film was characterized, and the leakage current was found to be well below 10{sup −6} A cm{sup −2}. - Highlights: • Preparation of thermal-curable hybrid materials using epoxy resin and silica. • The thermal stability was enhanced through hybridization. • The insulation property of hybrid film was investigated as gate dielectrics.
Scaled density functional theory correlation functionals.
Ghouri, Mohammed M; Singh, Saurabh; Ramachandran, B
2007-10-18
We show that a simple one-parameter scaling of the dynamical correlation energy estimated by the density functional theory (DFT) correlation functionals helps increase the overall accuracy for several local and nonlocal functionals. The approach taken here has been described as the "scaled dynamical correlation" (SDC) method [Ramachandran, J. Phys. Chem. A 2006, 110, 396], and its justification is the same as that of the scaled external correlation (SEC) method of Brown and Truhlar. We examine five local and five nonlocal (hybrid) DFT functionals, the latter group including three functionals developed specifically for kinetics by the Truhlar group. The optimum scale factors are obtained by use of a set of 98 data values consisting of molecules, ions, and transition states. The optimum scale factors, found with a linear regression relationship, are found to differ from unity with a high degree of correlation in nearly every case, indicating that the deviation of calculated results from the experimental values are systematic and proportional to the dynamic correlation energy. As a consequence, the SDC scaling of dynamical correlation decreases the mean errors (signed and unsigned) by significant amounts in an overwhelming majority of cases. These results indicate that there are gains to be realized from further parametrization of several popular exchange-correlation functionals.
Alipour, Mojtaba; Karimi, Niloofar
2017-06-01
Organic light emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) emitters are an attractive category of materials that have witnessed a booming development in recent years. In the present contribution, we scrutinize the accountability of parameterized and parameter-free single-hybrid (SH) and double-hybrid (DH) functionals through the two formalisms, full time-dependent density functional theory (TD-DFT) and Tamm-Dancoff approximation (TDA), for the estimation of photophysical properties like absorption energy, emission energy, zero-zero transition energy, and singlet-triplet energy splitting of TADF molecules. According to our detailed analyses on the performance of SHs based on TD-DFT and TDA, the TDA-based parameter-free SH functionals, PBE0 and TPSS0, with one-third of exact-like exchange turned out to be the best performers in comparison to other functionals from various rungs to reproduce the experimental data of the benchmarked set. Such affordable SH approximations can thus be employed to predict and design the TADF molecules with low singlet-triplet energy gaps for OLED applications. From another perspective, considering this point that both the nonlocal exchange and correlation are essential for a more reliable description of large charge-transfer excited states, applicability of the functionals incorporating these terms, namely, parameterized and parameter-free DHs, has also been evaluated. Perusing the role of exact-like exchange, perturbative-like correlation, solvent effects, and other related factors, we find that the parameterized functionals B2π-PLYP and B2GP-PLYP and the parameter-free models PBE-CIDH and PBE-QIDH have respectable performance with respect to others. Lastly, besides the recommendation of reliable computational protocols for the purpose, hopefully this study can pave the way toward further developments of other SHs and DHs for theoretical explorations in the field of OLEDs technology.
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...... spectrum at ambient pressure relate, for some parameter choices, well to peak positions in the calculated density of states function of Am-I....
Thompson, Joshua A.
2012-05-22
Zeolitic imidazolate frameworks (ZIFs) are a subclass of nanoporous metal-organic frameworks (MOFs) that exhibit zeolite-like structural topologies and have interesting molecular recognition properties, such as molecular sieving and gate-opening effects associated with their pore apertures. The synthesis and characterization of hybrid ZIFs with mixed linkers in the framework are described in this work, producing materials with properties distinctly different from the parent frameworks (ZIF-8, ZIF-90, and ZIF-7). NMR spectroscopy is used to assess the relative amounts of the different linkers included in the frameworks, whereas nitrogen physisorption shows the evolution of the effective pore size distribution in materials resulting from the framework hybridization. X-ray diffraction shows these hybrid materials to be crystalline. In the case of ZIF-8-90 hybrids, the cubic space group of the parent frameworks is continuously maintained, whereas in the case of the ZIF-7-8 hybrids there is a transition from a cubic to a rhombohedral space group. Nitrogen physisorption data reveal that the hybrid materials exhibit substantial changes in gate-opening phenomena, either occurring at continuously tunable partial pressures of nitrogen (ZIF-8-90 hybrids) or loss of gate-opening effects to yield more rigid frameworks (ZIF-7-8 hybrids). With this synthetic approach, significant alterations in MOF properties may be realized to suit a desired separation or catalytic process. © 2012 American Chemical Society.
A New Hybrid Model of Amino Acid Substitution for Protein Functional Classification
Institute of Scientific and Technical Information of China (English)
Ke Long WANG; Zhi Ning WEN; Fu Sheng NIE; Meng Long LI
2005-01-01
In this paper, a new hybrid model of amino acid substitution is developed and compared with the others in previous works. The results show that the new hybrid model can characterize the protein sequences very well by calculating Fisher weights, which can denote how much the variants contribute to the classification.
Directory of Open Access Journals (Sweden)
Tarek El-Bialy
2010-03-01
Full Text Available Tarek El-Bialy1, Ali Hasan2, Ahmad Janadas3, Tarik Albaghdadi41Division of Orthodontics, Department of Dentistry, University of Alberta, Edmonton, Alberta, Canada; 2Division of Orthodontics, Department of Preventive Dental Sciences, Faculty of Dentistry; 3Division of Oral and Maxillofacial Surgery, Department of Oral and Maxillofacial Surgery, Faculty of Dentistry; 4Division of Radiology, Faculty of Medicine, King Abdul Aziz University, Jeddah, Saudi ArabiaAim: Conventional treatment of patients with hemifacial microsomia involves orthognathic surgery and/or distraction osteogenesis of the mandible. Previous reports showed that low-intensity pulsed ultrasound (LIPUS enhances mandibular growth in growing rabbits and monkeys. In monkeys, LIPUS enhanced mandibular growth when combined with functional jaw orthopedic appliances. The purpose of this pilot study was to investigate if LIPUS could enhance mandibular growth in children with hemifacial microsomia.Methods: Five children (age range 3–11 years with hemifacial microsomia were treated with hybrid jaw orthopedic functional appliances and treatment of the affected mandibular condyle by LIPUS for 20 minutes per day.Results: The results showed that after one year of treatment, significant improvement of the underdeveloped side of patients’ faces and mandibles was recognized both clinically and radiographically.Discussion: Although improvement took a longer time than did a surgical approach, optimizing this technique may achieve better results in a shorter treatment time. A randomized controlled clinical trial to investigate the effect of optimized LIPUS application or functional appliances in the treatment of hemifacial microsomia is warranted.Keywords: hemifacial microsomia, LIPUS, non-surgical treatment, children
Range-separated meta-GGA functional designed for noncovalent interactions
Modrzejewski, Marcin; Szczęśniak, Małgorzata M
2014-01-01
The accuracy of applying density functional theory to noncovalent interactions is hindered by errors arising from low-density regions of interaction-induced change in the density gradient, error compensation between correlation and exchange functionals, and dispersion double counting. A new exchange-correlation functional designed for noncovalent interactions is proposed to address these problems. The functional consists of the range-separated PBEsol exchange considered in two variants, pure and hybrid, and the semilocal correlation functional of Modrzejewski et al. [J. Chem. Phys. 137, 204121 (2012)] designed with the constraint satisfaction technique to smoothly connect with a dispersion term. Two variants of dispersion correction are appended to the correlation functional: the atom-atom pairwise additive DFT-D3 model and the density-dependent many-body dispersion with self-consistent screening (MBD-rsSCS). From these building blocks a set of four functionals is created to systematically examine the role of...
Towards efficient orbital-dependent density functionals for weak and strong correlation
Zhang, Igor Ying; Perdew, John P; Scheffler, Matthias
2016-01-01
We present a new paradigm for the design of exchange-correlation functionals in density-functional theory. Electron pairs are correlated explicitly by means of the recently developed second order Bethe-Goldstone equation (BGE2) approach. Here we propose a screened BGE2 (sBGE2) variant that efficiently regulates the coupling of a given electron pair. sBGE2 correctly dissociates H$_2$ and H$_2^+$, a problem that has been regarded as a great challenge in density-functional theory for a long time. The sBGE2 functional is then taken as a building block for an orbital-dependent functional, termed ZRPS, which is a natural extension of the PBE0 hybrid functional. While worsening the good performance of sBGE2 in H$_2$ and H$_2^{+}$, ZRPS yields a remarkable and consistent improvement over other density functionals across various chemical environments from weak to strong correlation.
Engineering of a bio-functionalized hybrid off-the-shelf heart valve.
Hinderer, Svenja; Seifert, Jan; Votteler, Miriam; Shen, Nian; Rheinlaender, Johannes; Schäffer, Tilman E; Schenke-Layland, Katja
2014-02-01
Currently available heart valve replacements are limited in long-term performance or fail due to leaflet thickening, lack of growth or remodeling potential. In order to address these issues, it is necessary to mimic multiple factors of the native valvular extracellular matrix (ECM) such as architecture, mechanical behavior and biochemical signals. Here, we successfully generated an electrospun PEGdma-PLA scaffold adapted to the structure and mechanical properties of native valve leaflets. Valvular interstitial cells (VICs) and valvular endothelial cells (VECs) were seeded on the scaffold and when cultured under physiological conditions in a bioreactor, the construct performed like a native leaflet. Atomic force microscopy (AFM) was employed to obtain detailed mechanical information from the leaflets, which enabled the first layer-specific measurement of the Young's modulus. Interestingly, spongiosa stiffness was much lower compared to the fibrosa and ventricularis. Moreover, investigations into human fetal heart valve development identified collagen type I and versican as important structural proteins. As a proof of principle, these proteins were introduced to the scaffold, demonstrating the ability to bio-functionalize the hybrid valve based on natures' blueprint.
Uncertain Quality Function Deployment Using a Hybrid Group Decision Making Model
Directory of Open Access Journals (Sweden)
Ze-Ling Wang
2016-11-01
Full Text Available Quality function deployment (QFD is a widely used quality system tool for translating customer requirements (CRs into the engineering design requirements (DRs of products or services. The conventional QFD analysis, however, has been criticized as having some limitations such as in the assessment of relationships between CRs and DRs, the determination of CR weights and the prioritization of DRs. This paper aims to develop a new hybrid group decision-making model based on hesitant 2-tuple linguistic term sets and an extended QUALIFLEX (qualitative flexible multiple criteria method approach for handling QFD problems with incomplete weight information. First, hesitant linguistic term sets are combined with interval 2-tuple linguistic variables to express various uncertainties in the assessment information of QFD team members. Borrowing the idea of grey relational analysis (GRA, a multiple objective optimization model is constructed to determine the relative weights of CRs. Then, an extended QUALIFLEX approach with an inclusion comparison method is suggested to determine the ranking of the DRs identified in QFD. Finally, an analysis of a market segment selection problem is conducted to demonstrate and validate the proposed QFD approach.
Predictive functional control of temperature in a pharmaceutical hybrid nonlinear batch reactor
Directory of Open Access Journals (Sweden)
Štampar Simon
2013-01-01
Full Text Available These days, in times of recession, we are forced by competitiveness and the optimization of production to lower the costs of the temperature control in pharmaceutical batch reactors and increase the quantity and quality of the produced pharmaceutical product (active pharmaceutical substances. Therefore, a control algorithm is needed which provides us rapid and precise temperature control. This paper deals with the development of a control algorithm, where two predictive functional controllers are connected in a cascade for heating and cooling the content of the hybrid batch reactor. The algorithm has to be designed to cope with the constraints and the mixed discrete and continuous nature of the process of heating and cooling. The main goal of the control law is to achieve rapid and exact tracking of the reference temperature, good disturbance rejection and, in particular, a small number of heating and cooling medium switchings. The simulation results of the proposed algorithm give us much better performance compared to a conventional cascade PI algorithm.
Marangos, P J; Zis, A P; Clark, R L; Goodwin, F K
1978-07-07
Three forms of the glycolytic enzyme, enolase [2-phospho-D-glycerate hydrolase (E.C. No. 4.2.1.11)] have been prepared from rat whole brain extract. The most acidic enolase form is neuron specific enolase (NSE) which had previously been designated neuron specific protein (NSP). The least acidic form designated non-neuronal enolase (NNE) has been purified and compared structurally, immunologically and functionally to NSE. NNE is a dimer of 86,500 M.W. consistint of two very similar subunits. The data establish that NNE is larger than NSE which has been shown to be composed of two apparently identical 39,000 molecular weight subunits (78,000). NNE is less acidic than NSE having a pI of 5.9 compared to the value of 4.7 for NSE. Structural and immunological analysis establishes that the NNE subunit is distinct from the NSE subunit, and are therfore products of two separate genes. The structural designation of NSE is (gammagamma) and that of NNE (alpha' alpha'). NSE is strictly localized in neurons indicating that the gene coding for the gamma subunit is only expressed in neuronal cells. The intermediate brain enolase form has been partially purified; structural and immunological evidence indicate that it is a hybrid molecule consisting of one NNE subunit and one NSE subunit (alpha'gamma).
Preparation and characterization of functional material based on hybrid polymer composites
Agusu, La; Amiruddin; Taswito, Chen Chen; Herdianto; Zamrun, Muh.
2016-08-01
The microstructures and properties of hybrid polymer composites based on polyaniline (PANi)/γ-Fe2O3 nanoparticles/TiO2/carbon have been investigated for multifunctional applications such as heavy metal removal and initial study for radar absorbing material application. γ-Fe2O3 nanoparticles with spherical shape were synthetized by a coprecipitation method from iron sand. By activating the polyethylene glycol (PEG-400) coated carbon of coconut shell, the homogenous shape and size of carbon was achieved. Then, γ- Fe2O3, TiO2, and carbon were mixed with PANi by an in situ polymerization method at low temperature 0-5 oC. Characterization process involved XRD, SEM, FTIR, VSM, and DC conductivity measurements. For radar absorber application, the functionalized polymer composites showed good electrical conductivity 0.45 S/cm to absorb the incoming electromagnetic energy. An efficient and effective reduction of Pb2+ ion from the water has been achieved by using this material.
Huang, Huisheng; Zhang, Tonglai; Zhang, Jianguo; Wang, Liqiong
2010-07-15
The molecular geometry, electronic structure, infrared spectra and thermochemical properties of cobalt and nickel tris(carbohydrazide) perchlorates (CoCP and NiCP) as well as copper bis(carbohydrazide) perchlorate (CuCP) were investigated using the Heyd-Scuseria-Ernzerhof (HSE) screened hybrid density functional. The results show that both perchlorate ions coordinate with the copper atom, and the interactions between copper and perchlorate are ionic, whereas all the metal-carbohydrazide interactions are covalent. Due to the delocalization from the sigma(N-H) bond orbital to the n*(M) antibond orbital, the amino stretching vibrations of these complexes show considerable red-shift compared with those of free carbohydrazide ligand. The calculated heats of reaction and formation indicate that the formations of these complexes are exothermic, and the order of their thermal stability is NiCP>CoCP>CuCP. These agree well with the experimental results. Finally, we find that there is a relationship between the energy gap and impact sensitivity.
Hematite(001)-liquid water interface from hybrid density functional-based molecular dynamics
Falk von Rudorff, Guido; Jakobsen, Rasmus; Rosso, Kevin M.; Blumberger, Jochen
2016-10-01
The atom-scale characterisation of interfaces between transition metal oxides and liquid water is fundamental to our mechanistic understanding of diverse phenomena ranging from crystal growth to biogeochemical transformations to solar fuel production. Here we report on the results of large-scale hybrid density functional theory-based molecular dynamics simulations for the hematite(001)-liquid water interface. A specific focus is placed on understanding how different terminations of the same surface influence surface solvation. We find that the two dominant terminations for the hematite(001) surface exhibit strong differences both in terms of the active species formed on the surface and the strength of surface solvation. According to present simulations, we find that charged oxyanions (-O-) and doubly protonated oxygens (-OH2+ ) can be formed on the iron terminated layer via autoionization of neutral -OH groups. No such charged species are found for the oxygen terminated surface. In addition, the missing iron sublayer in the iron terminated surface strongly influences the solvation structure, which becomes less well ordered in the vicinity of the interface. These pronounced differences are likely to affect the reactivity of the two surface terminations, and in particular the energetics of excess charge carriers at the surface.
Calculation of point defects in rutile TiO2 by the Screened Exchange Hybrid Functional
Lee, Hsin-Yi; Robertson, John
2012-01-01
The formation energies of the oxygen vacancy and titanium interstitial in rutile TiO2 were calculated by the screened exchange (sX) hybrid density functional method, which gives a band gap of 3.1 eV, close to the experimental value. The O vacancy gives rise to a gap state lying 0.7 eV below the conduction band edge, whose charge density is localised around the two of three Ti atoms next to the vacancy. The Ti interstitial generates four defect states in the gap, whose unpaired electrons lie on the interstitial and the adjacent Ti 3d orbitals. The formation energy for the neutral O vacancy is 1.9 eV for the O-poor chemical potential, and similar to that of the neutral Ti interstitial, and has a lower formation energy for Ti interstitial under O-rich conditions. This indicates that both the O vacancy and Ti interstitial are relevant for oxygen deficiency in rutile TiO2 but the O vacancy will dominate under O-rich conditions. This resolves the questions about defect localisation and defect predominance in the li...
Energy Technology Data Exchange (ETDEWEB)
Xu, Jun [Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China); Jia, Lei [Department of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000 (China); Ma, Yufei; Liu, Xiao; Tian, Hao; Liu, Weisheng [Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China); Tang, Yu, E-mail: tangyu@lzu.edu.cn [Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000 (China)
2012-09-14
Functional luminescent hybrid materials have emerged as fascinating and promising materials for their versatile applications. In this report, novel efficient luminescent lanthanide (Tb{sup 3+}, Eu{sup 3+}) hybrid materials with a new kind of amide-type {beta}-diketone ligands covalently bonded to the silica gels have been assembled through the sol-gel progresses. The hybrid materials have been characterized by the Fourier transform infrared (FTIR) spectra, UV-vis absorption spectra, powder X-ray diffraction (PXRD), scanning electron microscope (SEM), and thermal analyses. The relationship between structures and photophysical behaviors of these materials was discussed in detail. The materials assembled by the precursors containing aromatic end group (Si-L{sup 1}-Ln) exhibited longer luminescence lifetimes and higher quantum efficiencies, suggesting that the existence of a suitable conjugated system should allow a more efficient energy transfer. Under UV irradiation, the materials emitted either bright green light or red light with different intensity which may lead to potential functional applications in optical devices and electronic devices. Highlights: Black-Right-Pointing-Pointer A new kind of efficient luminescent lanthanide hybrid materials has been assembled. Black-Right-Pointing-Pointer The materials can efficiently emit green or red light under UVA irradiation. Black-Right-Pointing-Pointer The relationship between photophysical behaviors and structures was discussed. Black-Right-Pointing-Pointer A suitable conjugated system should allow a more efficient energy transfer.
Energy Technology Data Exchange (ETDEWEB)
Xu, Ting; Zhao, Xin; Zhang, Junxian; Dong, Jie; Zhang, Qinghua, E-mail: qhzhang@dhu.edu.cn
2016-04-30
Highlights: • PS/PDA with well-defined core/shell structures was prepared in aqueous solution. • Au NPs were coated on PS/PDA by in-situ reduction and self-assembly approach. • PS/PDA/Au had homogeneous and dense Au coatings with different shape. • Hierarchical spheres exhibited a well-defined core/shell structure maintaining the spherical morphology. - Abstract: Two kinds of ternary hybrids were prepared by anchoring different shapes and loadings of Au nanoparticles (NPs) on poly(dopamine) (PDA) functionalized polystyrene (PS) microspheres with two different strategies, i.e., in situ reduction and self-assembly approach. PDA coatings were firstly introduced to functionalize the hydrophobic PS surface with sufficient amino and hydroxyl groups, which enhanced the interaction between Au NPs and the polymer spheres. Thus, Au NPs could be easily immobilized onto the surface of the PDA/PS microspheres, and the hierarchical composite microspheres exhibited a well-defined core/shell structure without sacrificing the spherical PS morphology. PS/PDA/Au-R and PS/PDA/Au-A microspheres fabricated by in situ reduction and self-assembly approach showed different distinct Au nano-shell morphology with the corresponding optical, catalytic and electrochemical properties. Field emission scanning electron microscopy and transmission electronic microscopy verified these hierarchical structures with the ultrathin PDA film incorporating between the inner PS core and the outer Au NPs shell. X-ray diffraction and X-ray photoelectron spectroscopy confirmed the presence of PDA and Au layer on the surface of the composite particles. These green and facile methods with mild experimental conditions can extend to fabricate other polymer or inorganic substrates coated by various noble metals.
Excitation Gaps of Finite-Sized Systems from Optimally Tuned Range-Separated Hybrid Functionals.
Kronik, Leeor; Stein, Tamar; Refaely-Abramson, Sivan; Baer, Roi
2012-05-08
Excitation gaps are of considerable significance in electronic structure theory. Two different gaps are of particular interest. The fundamental gap is defined by charged excitations, as the difference between the first ionization potential and the first electron affinity. The optical gap is defined by a neutral excitation, as the difference between the energies of the lowest dipole-allowed excited state and the ground state. Within many-body perturbation theory, the fundamental gap is the difference between the corresponding lowest quasi-hole and quasi-electron excitation energies, and the optical gap is addressed by including the interaction between a quasi-electron and a quasi-hole. A long-standing challenge has been the attainment of a similar description within density functional theory (DFT), with much debate on whether this is an achievable goal even in principle. Recently, we have constructed and applied a new approach to this problem. Anchored in the rigorous theoretical framework of the generalized Kohn-Sham equation, our method is based on a range-split hybrid functional that uses exact long-range exchange. Its main novel feature is that the range-splitting parameter is not a universal constant but rather is determined from first principles, per system, based on satisfaction of the ionization potential theorem. For finite-sized objects, this DFT approach mimics successfully, to the best of our knowledge for the first time, the quasi-particle picture of many-body theory. Specifically, it allows for the extraction of both the fundamental and the optical gap from one underlying functional, based on the HOMO-LUMO gap of a ground-state DFT calculation and the lowest excitation energy of a linear-response time-dependent DFT calculation, respectively. In particular, it produces the correct optical gap for the difficult case of charge-transfer and charge-transfer-like scenarios, where conventional functionals are known to fail. In this perspective, we overview
Redox levels in aqueous solution: Effect of van der Waals interactions and hybrid functionals
Ambrosio, Francesco; Miceli, Giacomo; Pasquarello, Alfredo
2015-12-01
We investigate redox levels in aqueous solution using a combination of ab initio molecular dynamics (MD) simulations and thermodynamic integration methods. The molecular dynamics are performed with both the semilocal Perdew-Burke-Ernzerhof functional and a nonlocal functional (rVV10) accounting for van der Waals (vdW) interactions. The band edges are determined through three different schemes, namely, from the energy of the highest occupied and of the lowest unoccupied Kohn-Sham states, from total-energy differences, and from a linear extrapolation of the density of states. It is shown that the latter does not depend on the system size while the former two are subject to significant finite-size effects. For the redox levels, we provide a formulation in analogy to the definition of charge transition levels for defects in crystalline materials. We consider the H+/H2 level defining the standard hydrogen electrode, the OH-/OH∗ level corresponding to the oxidation of the hydroxyl ion, and the H2O/OH∗ level for the dehydrogenation of water. In spite of the large structural modifications induced in liquid water, vdW interactions do not lead to any significant structural effect on the calculated band gap and band edges. The effect on the redox levels is also small since the solvation properties of ionic species are little affected by vdW interactions. Since the electronic properties are not significantly affected by the underlying structural properties, it is justified to perform hybrid functional calculations on the configurations of our MD simulations. The redox levels calculated as a function of the fraction α of Fock exchange are found to remain constant, reproducing a general behavior previously observed for charge transition levels of defects. Comparison with experimental values shows very good agreement. At variance, the band edges and the band gap evolve linearly with α. For α ≃ 0.40, we achieve a band gap, band-edge positions, and redox levels in overall
Redox levels in aqueous solution: Effect of van der Waals interactions and hybrid functionals
Energy Technology Data Exchange (ETDEWEB)
Ambrosio, Francesco, E-mail: Francesco.Ambrosio@epfl.ch; Miceli, Giacomo; Pasquarello, Alfredo [Chaire de Simulation à l’Echelle Atomique (CSEA), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)
2015-12-28
We investigate redox levels in aqueous solution using a combination of ab initio molecular dynamics (MD) simulations and thermodynamic integration methods. The molecular dynamics are performed with both the semilocal Perdew-Burke-Ernzerhof functional and a nonlocal functional (rVV10) accounting for van der Waals (vdW) interactions. The band edges are determined through three different schemes, namely, from the energy of the highest occupied and of the lowest unoccupied Kohn-Sham states, from total-energy differences, and from a linear extrapolation of the density of states. It is shown that the latter does not depend on the system size while the former two are subject to significant finite-size effects. For the redox levels, we provide a formulation in analogy to the definition of charge transition levels for defects in crystalline materials. We consider the H{sup +}/H{sub 2} level defining the standard hydrogen electrode, the OH{sup −}/OH{sup ∗} level corresponding to the oxidation of the hydroxyl ion, and the H{sub 2}O/OH{sup ∗} level for the dehydrogenation of water. In spite of the large structural modifications induced in liquid water, vdW interactions do not lead to any significant structural effect on the calculated band gap and band edges. The effect on the redox levels is also small since the solvation properties of ionic species are little affected by vdW interactions. Since the electronic properties are not significantly affected by the underlying structural properties, it is justified to perform hybrid functional calculations on the configurations of our MD simulations. The redox levels calculated as a function of the fraction α of Fock exchange are found to remain constant, reproducing a general behavior previously observed for charge transition levels of defects. Comparison with experimental values shows very good agreement. At variance, the band edges and the band gap evolve linearly with α. For α ≃ 0.40, we achieve a band gap, band
Tunable functionalization of graphene nanosheets for graphene-organic hybrid photodetectors
Kim, Seong Jun; Song, Wooseok; Kim, Sungho; Kang, Min-A.; Myung, Sung; Lee, Sun Sook; Lim, Jongsun; An, Ki-Seok
2016-02-01
Graphene-organic hybrid thin films are promising candidates for use as advanced transparent electrodes and high-performance photodetectors. In this work, we fabricated hybrid thin film structures consisting of graphene and either tetraphenyl-porphyrin (H2TPP) or metalloporphyrins such as aluminum (III) tetraphenyl-porphyrin (Al(III)TPP) and zinc tetraphenyl-porphyrin (ZnTPP). The optical and electrical characteristics of ultrathin photodetectors based on the graphene-organic hybrid layers were subsequently evaluated. A hybrid deposition system capable of both thermal evaporation and vapor phase metalation was employed to synthesize the tunable metalloporphyrin-based thin films. As a proof of concept, we successfully fabricated various graphene-based photodetectors via the simple and efficient vapor-phase metalation of porphyrin. This work may facilitate the development of new architectures for flexible graphene-organic devices.
Santra, Biswajit; Michaelides, Angelos; Fuchs, Martin; Tkatchenko, Alexandre; Filippi, Claudia; Scheffler, Matthias
2008-01-01
Second order Møller–Plesset perturbation theory at the complete basis set limit and diffusion quantum Monte Carlo are used to examine several low energy isomers of the water hexamer. Both approaches predict the so-called prism to be the lowest energy isomer, followed by cage, book, and cyclic isomer
Magnetism in Sc-doped ZnO with zinc vacancies: A hybrid density functional and GGA + U approaches
Kanoun, Mohammed
2012-04-01
We investigate the zinc vacancy effects on the electronic structures and magnetic properties of Sc-doped ZnO, by performing first-principles calculations within both GGA + U and Heyd-Scuseria-Ernzerhof hybrid functional methods. We find that Sc impurities stabilize considerably Zn vacancies. The electronic and magnetic analysis shows a half metallic ferromagnetic character with a total magnetic moment of 2.01 μ B. The magnetism mainly stems from the O 2p states around the Zn vacancies. Calculations with the hybrid density functional agree with the GGA + U results but give an accurate description of the electronic structure for pure ZnO and Sc-doped ZnO with Zn vacancies. © 2012 Elsevier B.V. All rights reserved.
Berland, Kristian; Jiao, Yang; Lee, Jung-Hoon; Rangel, Tonatiuh; Neaton, Jeffrey B.; Hyldgaard, Per
2017-06-01
Two hybrid van der Waals density functionals (vdW-DFs) are developed using 25% Fock exchange with (i) the consistent-exchange vdW-DF-cx functional [K. Berland and P. Hyldgaard, Phys. Rev. B 89, 035412 (2014)] and (ii) with the vdW-DF2 functional [K. Lee et al., Phys. Rev. B 82, 081101 (2010)]. The ability to describe covalent and non-covalent binding properties of molecules is assessed. For properties related to covalent binding, atomization energies (G2-1 set), molecular reaction energies (G2RC set), and ionization energies (G21IP set) are benchmarked against experimental reference values. We find that hybrid-vdW-DF-cx yields results that are rather similar to those of the standard non-empirical hybrid PBE0 [C. Adamo and V. Barone, J. Chem. Phys. 110, 6158 (1999)], with mean average deviations (MADs) of 4.9 and 5.0 kcal/mol for the G2-1 set, respectively. In this comparison, experimental reference values are used, back corrected by wavefunction-based quantum-chemistry calculations of zero-point energies. Hybrid vdW-DF2 follows somewhat different trends, showing on average significantly larger deviations from the reference energies, with a MAD of 14.5 kcal/mol for the G2-1 set. Non-covalent binding properties of molecules are assessed using the S22 benchmark set of non-covalently bonded dimers and the X40 set of dimers of small halogenated molecules, using wavefunction-based quantum chemistry results as references. For the S22 set, hybrid-vdW-DF-cx performs better than standard vdW-DF-cx for the mostly hydrogen-bonded systems, with MAD dropping from 0.6 to 0.3 kcal/mol, but worse for purely dispersion-bonded systems, with MAD increasing from 0.2 to 0.6 kcal/mol. Hybrid-vdW-DF2 offers a slight improvement over standard vdW-DF2. Similar trends are found for the X40 set, with hybrid-vdW-DF-cx performing particularly well for binding energies involving the strongly polar hydrogen halides, but poorly for systems with tiny binding energies. Our study of the X40 set
A Hybrid Approach to Structure and Function Modeling of G Protein-Coupled Receptors.
Latek, Dorota; Bajda, Marek; Filipek, Sławomir
2016-04-25
The recent GPCR Dock 2013 assessment of serotonin receptor 5-HT1B and 5-HT2B, and smoothened receptor SMO targets, exposed the strengths and weaknesses of the currently used computational approaches. The test cases of 5-HT1B and 5-HT2B demonstrated that both the receptor structure and the ligand binding mode can be predicted with the atomic-detail accuracy, as long as the target-template sequence similarity is relatively high. On the other hand, the observation of a low target-template sequence similarity, e.g., between SMO from the frizzled GPCR family and members of the rhodopsin family, hampers the GPCR structure prediction and ligand docking. Indeed, in GPCR Dock 2013, accurate prediction of the SMO target was still beyond the capabilities of most research groups. Another bottleneck in the current GPCR research, as demonstrated by the 5-HT2B target, is the reliable prediction of global conformational changes induced by activation of GPCRs. In this work, we report details of our protocol used during GPCR Dock 2013. Our structure prediction and ligand docking protocol was especially successful in the case of 5-HT1B and 5-HT2B-ergotamine complexes for which we provide one of the most accurate predictions. In addition to a description of the GPCR Dock 2013 results, we propose a novel hybrid computational methodology to improve GPCR structure and function prediction. This computational methodology employs two separate rankings for filtering GPCR models. The first ranking is ligand-based while the second is based on the scoring scheme of the recently published BCL method. In this work, we prove that the use of knowledge-based potentials implemented in BCL is an efficient way to cope with major bottlenecks in the GPCR structure prediction. Thereby, we also demonstrate that the knowledge-based potentials for membrane proteins were significantly improved, because of the recent surge in available experimental structures.
Miglia, K.J.; McArthur, E.D.; Redman, R.S.; Rodriguez, R.J.; Zak, J.C.; Freeman, D.C.
2007-01-01
When addressing the nature of ecological adaptation and environmental factors limiting population ranges and contributing to speciation, it is important to consider not only the plant's genotype and its response to the environment, but also any close interactions that it has with other organisms, specifically, symbiotic microorganisms. To investigate this, soils and seedlings were reciprocally transplanted into common gardens of the big sagebrush hybrid zone in Salt Creek Canyon, Utah, to determine location and edaphic effects on the fitness of parental and hybrid plants. Endophytic symbionts and functional microbial diversity of indigenous and transplanted soils and sagebrush plants were also examined. Strong selection occurred against the parental genotypes in the middle hybrid zone garden in middle hybrid zone soil; F1 hybrids had the highest fitness under these conditions. Neither of the parental genotypes had superior fitness in their indigenous soils and habitats; rather F1 hybrids with the nonindigenous maternal parent were superiorly fit. Significant garden-by-soil type interactions indicate adaptation of both plant and soil microorganisms to their indigenous soils and habitats, most notably in the middle hybrid zone garden in middle hybrid zone soil. Contrasting performances of F1 hybrids suggest asymmetrical gene flow with mountain, rather than basin, big sagebrush acting as the maternal parent. We showed that the microbial community impacted the performance of parental and hybrid plants in different soils, likely limiting the ranges of the different genotypes.
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.
Mo, Yuxiang; Car, Roberto; Staroverov, Viktor N.; Scuseria, Gustavo E.; Tao, Jianmin
2017-01-01
Recently, Tao and Mo developed a semilocal exchange-correlation density functional. The exchange part of this functional is derived from a density-matrix expansion corrected to reproduce the fourth-order gradient expansion of the exchange energy in the slowly-varying-density limit, while the correlation part is based on the Tao-Perdew-Staroverov-Scuseria (TPSS) correlation functional, with a modification for the low-density limit. In the present paper, the Tao-Mo (TM) functional is assessed by computing various properties of solids and jellium surfaces. This includes 22 lattice constants and bulk moduli, 30 band gaps, seven cohesive energies, and jellium surface exchange and correlation energies for the density parameter rs in the range from 2 to 3 bohr. Our calculations show that the TM approximation can yield consistently high accuracy for most properties considered here, with mean absolute errors (MAEs) of 0.025 Å for lattice constants, 7.0 GPa for bulk moduli, 0.08 eV/atom for cohesive energies, and 35 erg /c m2 for surface exchange-correlation energies. The MAE in band gaps is larger than that of TPSS, but slightly smaller than the errors of the local spin-density approximation, Perdew-Burke-Ernzerhof generalized gradient approximation, and revised TPSS. However, band gaps are still underestimated, particularly for large-gap semiconductors, compared to the Heyd-Scuseria-Ernzerhof nonlocal screened hybrid functional.
Kumar, Sant; Yadav, Umesh K.; Maitra, T.; Singh, Ishwar
2016-02-01
Ground state magnetic properties of the spin-dependent Falicov-Kimball model (FKM) are studied by incorporating the intrasite exchange correlation J (between itinerant d- and localized f-electrons) and intersite (superexchange) correlation Jse (between localized f-electrons) on a triangular lattice for two different fillings. Numerical diagonalization and Monte-Carlo techniques are used to determine the ground state magnetic properties. Transitions from antiferromagnetic to ferromagnetic and again to re-entrant antiferromagnetic phase is observed in a wide range of parameter space. The magnetic moments of d- and f-electrons are observed to depend strongly on the value of J, Jse and also on the total number of d-electrons (Nd).
March, N H; Nagy, A
2008-11-21
Following some studies of integral(n)(r)inverted DeltaV(r)dr by earlier workers for the density functional theory (DFT) one-body potential V(r) generating the exact ground-state density, we consider here the special case of spherical atoms. The starting point is the differential virial theorem, which is used, as well as the Hiller-Sucher-Feinberg [Phys. Rev. A 18, 2399 (1978)] identity to show that the scalar quantity paralleling the above vector integral, namely, integral(n)(r) partial differential(V)(r)/partial differential(r)dr, is determined solely by the electron density n(0) at the nucleus for the s-like atoms He and Be. The force - partial differential(V)/ partial differential(r) is then related to the derivative of the exchange-correlation potential V(xc)(r) by terms involving only the external potential in addition to n(r). The resulting integral constraint should allow some test of the quality of currently used forms of V(xc)(r). The article concludes with results from the differential virial theorem and the Hiller-Sucher-Feinberg identity for the exact many-electron theory of spherical atoms, as well as for the DFT for atoms such as Ne with a closed p shell.
Energy Technology Data Exchange (ETDEWEB)
Tao, Jianmin [Los Alamos National Laboratory; Perdew, John P [TULANE UNIV; Staroverov, Viktor N [UNIV OF WESTERN ONTARIO; Scuseria, Gustavo E [RICE UNIV
2008-01-01
We construct a nonlocal density functional approximation with full exact exchange, while preserving the constraint-satisfaction approach and justified error cancellations of simpler semilocal functionals. This is achieved by interpolating between different approximations suitable for two extreme regions of the electron density. In a 'normal' region, the exact exchange-correlation hole density around an electron is semilocal because its spatial range is reduced by correlation and because it integrates over a narrow range to -1. These regions are well described by popular semilocal approximations (many of which have been constructed nonempirically), because of proper accuracy for a slowly-varying density or because of error cancellation between exchange and correlation. 'Abnormal' regions, where non locality is unveiled, include those in which exchange can dominate correlation (one-electron, nonuniform high-density, and rapidly-varying limits), and those open subsystems of fluctuating electron number over which the exact exchange-correlation hole integrates to a value greater than -1. Regions between these extremes are described by a hybrid functional mixing exact and semi local exchange energy densities locally (i.e., with a mixing fraction that is a function of position r and a functional of the density). Because our mixing fraction tends to 1 in the high-density limit, we employ full exact exchange according to the rigorous definition of the exchange component of any exchange-correlation energy functional. Use of full exact exchange permits the satisfaction of many exact constraints, but the nonlocality of exchange also requires balanced nonlocality of correlation. We find that this nonlocality can demand at least five empirical parameters (corresponding roughly to the four kinds of abnormal regions). Our local hybrid functional is perhaps the first accurate size-consistent density functional with full exact exchange. It satisfies other known
Ihrig, Arvid Conrad; Wieferink, Jürgen; Zhang, Igor Ying; Ropo, Matti; Ren, Xinguo; Rinke, Patrick; Scheffler, Matthias; Blum, Volker
2015-09-01
A key component in calculations of exchange and correlation energies is the Coulomb operator, which requires the evaluation of two-electron integrals. For localized basis sets, these four-center integrals are most efficiently evaluated with the resolution of identity (RI) technique, which expands basis-function products in an auxiliary basis. In this work we show the practical applicability of a localized RI-variant (‘RI-LVL’), which expands products of basis functions only in the subset of those auxiliary basis functions which are located at the same atoms as the basis functions. We demonstrate the accuracy of RI-LVL for Hartree-Fock calculations, for the PBE0 hybrid density functional, as well as for RPA and MP2 perturbation theory. Molecular test sets used include the S22 set of weakly interacting molecules, the G3 test set, as well as the G2-1 and BH76 test sets, and heavy elements including titanium dioxide, copper and gold clusters. Our RI-LVL implementation paves the way for linear-scaling RI-based hybrid functional calculations for large systems and for all-electron many-body perturbation theory with significantly reduced computational and memory cost.
Erisken, Cevat
Tissue engineering is the application of the principles of engineering and life sciences for the development of biological alternatives for improvement or regeneration of native tissues. Native tissues are complex structures with functions and properties changing spatially and temporally, and engineering of such structures requires functionally graded scaffolds with composition and properties changing systematically along various directions. Utilization of a new hybrid technology integrating the controlled feeding, compounding, dispersion, deaeration, and pressurization capabilities of extrusion process with electrospinning allows incorporation of liquids and solid particles/nanoparticles into polymeric fibers/nanofibers for fabrication of functionally graded non-woven meshes to be used as scaffolds in engineering of tissues. The capabilities of the hybrid technology were demonstrated with a series of scaffold fabrication and cell culturing studies along with characterization of biomechanical properties. In the first study, the hybrid technology was employed to generate concentration gradations of beta-tricalcium phosphate (beta-TCP) nanoparticles in a polycaprolactone (PCL) binder, between two surfaces of nanofibrous scaffolds. These scaffolds were seeded with pre-osteoblastic cell line (MC3T3-E1) to attempt to engineer cartilage-bone interface, and after four weeks, the tissue constructs revealed formation of continuous gradations in extracellular matrix akin to cartilage-bone interface in terms of distributions of mineral concentrations and biomechanical properties. In a second demonstration of the hybrid technology, graded differentiation of stem cells was attempted by using insulin, a known stimulator of chondrogenic differentiation, and beta-glycerol phosphate (beta-GP), for mineralization. Concentrations of insulin and beta-GP in PCL were controlled to monotonically increase and decrease, respectively, along the length of scaffolds, which were then seeded
Directory of Open Access Journals (Sweden)
Jacky Even
2014-01-01
Full Text Available Potentialities of density functional theory (DFT based methodologies are explored for photovoltaic materials through the modeling of the structural and optoelectronic properties of semiconductor hybrid organic-inorganic perovskites and GaAs/GaP heterostructures. They show how the properties of these bulk materials, as well as atomistic relaxations, interfaces, and electronic band-lineups in small heterostructures, can be thoroughly investigated. Some limitations of available standard DFT codes are discussed. Recent improvements able to treat many-body effects or based on density-functional perturbation theory are also reviewed in the context of issues relevant to photovoltaic technologies.
Huyal, Ilkem Ozge; Ozel, Tuncay; Koldemir, Unsal; Nizamoglu, Sedat; Tuncel, Donus; Demir, Hilmi Volkan
2008-01-21
We develop and demonstrate high-quality white light generation that relies on the use of a single-type simple conjugated polymer of polyfluorene functionalized with azide groups (PFA) integrated on a near-UV LED platform. The high-quality white emission from the polyfluorene is achieved by using the azide functionalization to facilitate cross-linking intentionally when cast into solid-state form. Hybridized on n-UV InGaN/GaN LED at 378 nm, the PFA emitters collectively generate a very broad down-converting photoluminescence at longer wavelengths across the entirety of the visible spectrum, yielding high color rendering indices up to 91.
Functional stability of endothelial cells on a novel hybrid scaffold for vascular tissue engineering
Energy Technology Data Exchange (ETDEWEB)
Pankajakshan, Divya; Krishnan, Lissy K [Thrombosis Research Unit, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Poojapura, Trivandrum 695 012 (India); Krishnan V, Kalliyana, E-mail: lissykk@sctimst.ac.i [Division of Polymer Technology, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Poojapura, Trivandrum 695 012 (India)
2010-12-15
Porous and pliable conduits made of biodegradable polymeric scaffolds offer great potential for the development of blood vessel substitutes but they generally lack signals for cell proliferation, survival and maintenance of a normal phenotype. In this study we have prepared and evaluated porous poly({epsilon}-caprolactone) (PCL) integrated with fibrin composite (FC) to get a biomimetic hybrid scaffold (FC PCL) with the biological properties of fibrin, fibronectin (FN), gelatin, growth factors and glycosaminoglycans. Reduced platelet adhesion on a human umbilical vein endothelial cell-seeded hybrid scaffold as compared to bare PCL or FC PCL was observed, which suggests the non-thrombogenic nature of the tissue-engineered scaffold. Analysis of real-time polymerase chain reaction (RT-PCR) after 5 days of endothelial cell (EC) culture on a hybrid scaffold indicated that the prothrombotic von Willebrand factor and plasminogen activator inhibitor (PAI) were quiescent and stable. Meanwhile, dynamic expressions of tissue plasminogen activator (tPA) and endothelial nitric oxide synthase indicated the desired cell phenotype on the scaffold. On the hybrid scaffold, shear stress could induce enhanced nitric oxide release, which implicates vaso-responsiveness of EC grown on the tissue-engineered construct. Significant upregulation of mRNA for extracellular matrix (ECM) proteins, collagen IV and elastin, in EC was detected by RT-PCR after growing them on the hybrid scaffold and FC-coated tissue culture polystyrene (FC TCPS) but not on FN-coated TCPS. The results indicate that the FC PCL hybrid scaffold can accomplish a remodeled ECM and non-thrombogenic EC phenotype, and can be further investigated as a scaffold for cardiovascular tissue engineering. (communication)
Functional cationic nanomagnet-porphyrin hybrids for the photoinactivation of microorganisms.
Carvalho, Carla M B; Alves, Eliana; Costa, Liliana; Tomé, João P C; Faustino, Maria A F; Neves, Maria G P M S; Tomé, Augusto C; Cavaleiro, José A S; Almeida, Adelaide; Cunha, Angela; Lin, Zhi; Rocha, João
2010-12-28
Cationic nanomagnet-porphyrin hybrids were synthesized and their photodynamic therapy capabilities were investigated against the Gram (-) Escherichia coli bacteria, the Gram (+) Enterococcus faecalis bacteria and T4-like phage. The synthesis, structural characterization, photophysical properties, and antimicrobial activity of these new materials are discussed. The results show that these new multicharged nanomagnet-porphyrin hybrids are very stable in water and highly effective in the photoinactivation of bacteria and phages. Their remarkable antimicrobial activity, associated with their easy recovery, just by applying a magnetic field, makes these materials novel photosensitizers for water or wastewater disinfection.
Institute of Scientific and Technical Information of China (English)
Zha Qi-Lao; Sirendaoreji
2006-01-01
Some new exact solitary wave solutions of the Hybrid lattice and discrete mKdV lattice are obtained by using a hyperbolic function approach.This approach can also be applied to other nonlinear differential-difference equations.
Genovese, Luigi; Ospici, Matthieu; Deutsch, Thierry; Méhaut, Jean-François; Neelov, Alexey; Goedecker, Stefan
2009-07-21
We present the implementation of a full electronic structure calculation code on a hybrid parallel architecture with graphic processing units (GPUs). This implementation is performed on a free software code based on Daubechies wavelets. Such code shows very good performances, systematic convergence properties, and an excellent efficiency on parallel computers. Our GPU-based acceleration fully preserves all these properties. In particular, the code is able to run on many cores which may or may not have a GPU associated, and thus on parallel and massive parallel hybrid machines. With double precision calculations, we may achieve considerable speedup, between a factor of 20 for some operations and a factor of 6 for the whole density functional theory code.
Hassan Omar, Omar; la Gatta, Simona; Tangorra, Rocco Roberto; Milano, Francesco; Ragni, Roberta; Operamolla, Alessandra; Argazzi, Roberto; Chiorboli, Claudio; Agostiano, Angela; Trotta, Massimo; Farinola, Gianluca M
2016-07-20
The photosynthetic reaction center (RC) from the Rhodobacter sphaeroides bacterium has been covalently bioconjugated with a NIR-emitting fluorophore (AE800) whose synthesis was specifically tailored to act as artificial antenna harvesting light in the entire visible region. AE800 has a broad absorption spectrum with peaks centered in the absorption gaps of the RC and its emission overlaps the most intense RC absorption bands, ensuring a consistent increase of the protein optical cross section. The covalent hybrid AE800-RC is stable and fully functional. The energy collected by the artificial antenna is transferred to the protein via FRET mechanism, and the hybrid system outperforms by a noteworthy 30% the overall photochemical activity of the native protein under the entire range of visible light. This improvement in the optical characteristic of the photoenzyme demonstrates the effectiveness of the bioconjugation approach as a suitable route to new biohybrid materials for energy conversion, photocatalysis, and biosensing.
Liu, Zhen-Fei; Egger, David A.; Refaely-Abramson, Sivan; Kronik, Leeor; Neaton, Jeffrey B.
2017-03-01
The alignment of the frontier orbital energies of an adsorbed molecule with the substrate Fermi level at metal-organic interfaces is a fundamental observable of significant practical importance in nanoscience and beyond. Typical density functional theory calculations, especially those using local and semi-local functionals, often underestimate level alignment leading to inaccurate electronic structure and charge transport properties. In this work, we develop a new fully self-consistent predictive scheme to accurately compute level alignment at certain classes of complex heterogeneous molecule-metal interfaces based on optimally tuned range-separated hybrid functionals. Starting from a highly accurate description of the gas-phase electronic structure, our method by construction captures important nonlocal surface polarization effects via tuning of the long-range screened exchange in a range-separated hybrid in a non-empirical and system-specific manner. We implement this functional in a plane-wave code and apply it to several physisorbed and chemisorbed molecule-metal interface systems. Our results are in quantitative agreement with experiments, the both the level alignment and work function changes. Our approach constitutes a new practical scheme for accurate and efficient calculations of the electronic structure of molecule-metal interfaces.
Ingrosso, Chiara; Bianco, Giuseppe V; Corricelli, Michela; Comparelli, Roberto; Altamura, Davide; Agostiano, Angela; Striccoli, Marinella; Losurdo, Maria; Curri, M Lucia; Bruno, Giovanni
2015-02-25
A simple and facile solution-based procedure is implemented for decorating a large area, monolayer graphene film, grown by chemical vapor deposition, with size-tunable light absorbing colloidal PbS nanocrystals (NCs). The hybrid is obtained by exposing a large area graphene film to a solution of 1-pyrene butyric acid surface coated PbS NCs, obtained by a capping exchange procedure onto presynthesized organic-capped NCs. The results demonstrate that at the interface, multiple and cooperative π-π stacking interactions promoted by the pyrene ligand coordinating the NC surface lead to a successful anchoring of the nano-objects on the graphene platform which concomitantly preserves its aromatic structure. Interligand interactions provide organization of the nano-objects in highly interconnected nanostructured multilayer coatings, where the NCs retain geometry and composition. The resulting hybrid exhibits a sheet resistance lower than that of bare graphene, which is explained in terms of electronic communication in the hybrid, due to the interconnection of the NC film and to a hole transfer from photoexcited PbS NCs to graphene, channelled at the interface by pyrene. Such a direct electron coupling makes the manufactured hybrid material an interesting component for optoelectronics, sensors and for optical communication and information technology.
Kartsan, I. N.; Tyapkin, V. N.; Dmitriev, D. D.; Goncharov, A. E.; Zelenkov, P. V.; Kovalev, I. V.
2016-11-01
This paper considers the simulation of adaptive nulling mechanism patterns in hybrid reflector antenna systems with a 19-element feed element, in which the radiation pattern is formed as a cluster. Incidents of broadband and narrowband interference are studied in the article.
Xu, Guohui; Wang, Xiaolin; Deng, Chao; Teng, Xiaomei; Suuronen, Erik J; Shen, Zhenya; Zhong, Zhiyuan
2015-03-01
Injectable biodegradable hybrid hydrogels were designed and developed based on thiolated collagen (Col-SH) and multiple acrylate containing oligo(acryloyl carbonate)-b-poly(ethylene glycol)-b-oligo(acryloyl carbonate) (OAC-PEG-OAC) copolymers for functional cardiac regeneration. Hydrogels were readily formed under physiological conditions (37°C and pH 7.4) from Col-SH and OAC-PEG-OAC via a Michael-type addition reaction, with gelation times ranging from 0.4 to 8.1 min and storage moduli from 11.4 to 55.6 kPa, depending on the polymer concentrations, solution pH and degrees of substitution of Col-SH. The collagen component in the hybrid hydrogels retained its enzymatic degradability against collagenase, and the degradation time of the hydrogels increased with increasing polymer concentration. In vitro studies showed that bone marrow mesenchymal stem cells (BMSCs) exhibited rapid cell spreading and extensive cellular network formation on these hybrid hydrogels. In a rat infarction model, the infarcted left ventricle was injected with PBS, hybrid hydrogels, BMSCs or BMSC-encapsulating hybrid hydrogels. Echocardiography demonstrated that the hybrid hydrogels and BMSC-encapsulating hydrogels could increase the ejection fraction at 28 days compared to the PBS control group, resulting in improved cardiac function. Histology revealed that the injected hybrid hydrogels significantly reduced the infarct size and increased the wall thickness, and these were further improved with the BMSC-encapsulating hybrid hydrogel treatment, probably related to the enhanced engraftment and persistence of the BMSCs when delivered within the hybrid hydrogel. Thus, these injectable hybrid hydrogels combining intrinsic bioactivity of collagen, controlled mechanical properties and enhanced stability provide a versatile platform for functional cardiac regeneration.
Liu, Zhongshan; Ou, Junjie; Lin, Hui; Wang, Hongwei; Dong, Jing; Zou, Hanfa
2014-05-16
A polyhedral oligomeric silsesquioxane (POSS) hybrid monolith was simply prepared by using octaglycidyldimethylsilyl POSS (POSS-epoxy) and cystamine dihydrochloride as monomers via ring-opening polymerization. The effects of composition of prepolymerization solution and polycondensation temperature on the morphology and permeability of monolithic column were investigated in detail. The obtained POSS hybrid monolithic column showed 3D skeleton morphology and exhibited high column efficiency of ∼71,000 plates per meter in reversed-phase mechanism. Owing to this POSS hybrid monolith essentially possessing a great number of disulfide bonds, the monolith surface would expose thiol groups after reduction with dithiothreitol (DTT), which supplied active sites to functionalize with various alkene monomers via thiol-ene click reaction. The results indicated that the reduction with DTT could not destroy the 3D skeleton of hybrid monolith. Both stearyl methylacrylate (SMA) and benzyl methacrylate (BMA) were selected to functionalize the hybrid monolithic columns for reversed-phase liquid chromatography (RPLC), while [2-(methacryloyloxy)ethyl]-dimethyl-(3-sulfopropyl)-ammonium hydroxide (MSA) was used to modify the hybrid monolithic column in hydrophilic interaction chromatography (HILIC). These modified hybrid monolithic columns could be successfully applied for separation of small molecules with high efficiency. It is demonstrated that thiol-ene click reaction supplies a facile way to introduce various functional groups to the hybrid monolith possessing thiol groups. Furthermore, due to good permeability of the resulting hybrid monoliths, we also prepared long hybrid monolithic columns in narrow-bore capillaries. The highest column efficiency reached to ∼70,000 plates using a 1-m-long column of 75μm i.d. with a peak capacity of 147 for isocratic chromatography, indicating potential application in separation and analysis of complex biosamples. Copyright © 2014
El-Mellouhi, Fadwa; Lucero, Melissa J; Scuseria, Gustavo E
2011-01-01
We have calculated the properties of SrTiO3 (STO) using a wide array of density functionals ranging from standard semi-local functionals to modern range-separated hybrids, combined with several basis sets of varying size/quality. We show how these combination's predictive ability varies signi?cantly, both for STO's cubic and antiferrodistortive (AFD) phases, with the greatest variation in functional/basis set e?cacy seen in modeling the AFD phase. The screened hybrid functionals we utilized predict the structural properties of both phases in very good agreement with experiment, especially if used with large (but still computationally tractable) basis sets. The most accurate results presented in this study, namely those from HSE06/modi?ed-def2-TZVP, stand as the most accurate modeling of STO to date when compared to the literature; these results agree well with experimental structural and electronic properties as well as providing insight into the band structure alteration during the phase transition.
Directory of Open Access Journals (Sweden)
Rajiv Ranjan
Full Text Available BACKGROUND: Development of novel synthetic promoters with enhanced regulatory activity is of great value for a diverse range of plant biotechnology applications. METHODOLOGY: Using the Figwort mosaic virus full-length transcript promoter (F and the sub-genomic transcript promoter (FS sequences, we generated two single shuffled promoter libraries (LssF and LssFS, two multiple shuffled promoter libraries (LmsFS-F and LmsF-FS, two hybrid promoters (FuasFScp and FSuasFcp and two hybrid-shuffled promoter libraries (LhsFuasFScp and LhsFSuasFcp. Transient expression activities of approximately 50 shuffled promoter clones from each of these libraries were assayed in tobacco (Nicotiana tabacum cv. Xanthi protoplasts. It was observed that most of the shuffled promoters showed reduced activity compared to the two parent promoters (F and FS and the CaMV35S promoter. In silico studies (computer simulated analyses revealed that the reduced promoter activities of the shuffled promoters could be due to their higher helical stability. On the contrary, the hybrid promoters FuasFScp and FSuasFcp showed enhanced activities compared to F, FS and CaMV 35S in both transient and transgenic Nicotiana tabacum and Arabidopsis plants. Northern-blot and qRT-PCR data revealed a positive correlation between transcription and enzymatic activity in transgenic tobacco plants expressing hybrid promoters. Histochemical/X-gluc staining of whole transgenic seedlings/tissue-sections and fluorescence images of ImaGene Green™ treated roots and stems expressing the GUS reporter gene under the control of the FuasFScp and FSuasFcp promoters also support the above findings. Furthermore, protein extracts made from protoplasts expressing the human defensin (HNP-1 gene driven by hybrid promoters showed enhanced antibacterial activity compared to the CaMV35S promoter. SIGNIFICANCE/CONCLUSION: Both shuffled and hybrid promoters developed in the present study can be used as molecular tools to
Functionalized fatty-acid vesicles as soft-matter/polymer hybrid nanocontainers
DEFF Research Database (Denmark)
Löffler, Richard J.G.; Hansen, Per Lyngs; Klösgen, Beate Maria
2014-01-01
Delivery and removal of delicate material in controlled amounts to or from cellular targets is still a challenge in nanomedicine. A suggestion for a new soft-matter/polymer hybrid container system is presented here. It is based on the self-assembly of fatty acids into bilayer membranes and stabil......Delivery and removal of delicate material in controlled amounts to or from cellular targets is still a challenge in nanomedicine. A suggestion for a new soft-matter/polymer hybrid container system is presented here. It is based on the self-assembly of fatty acids into bilayer membranes...... and stabilized by a polymer scaffold. The polymers exhibit a reversible thermotropic conformational transition. In toto, the composite system shall yield a novel delivery system with permeability properties that can controlled upon the thermally induced expansion/ shrinking of the polymers. The system bears...
Sadegh Mehdi Aghaei; Ingrid Torres; Irene Calizo
2016-01-01
Silicene, a novel graphene-like material, has attracted a significant attention because of its potential applications for nanoelectronics. In this paper, we have theoretically investigated the structural stability of edge-hydrogenated and edge-fluorinated silicene nanoribbons (SiNRs) via first-principles calculations. Various edge forms of SiNRs including armchair edge, zigzag edge, Klein edge, reconstructed Klein edge, reconstructed pentagon-heptagon edge, and hybrid edges have been consider...
Corn stover fractions as a function of hybrid, maturity, site and year
Energy Technology Data Exchange (ETDEWEB)
Lizotte, P.L. [Laval Univ., Quebec City, PQ (Canada). Dept. des sols et de genie agroalimentaire; Savoie, P. [Agriculture and Agri-Food Canada, Quebec City, PQ (Canada); Lefsrud, M. [McGill Univ., Macdonald College, Ste-Anne-de-Bellevue, PQ (Canada). Dept. of Biosystems Engineering
2010-07-01
Corn stover is usually left on the ground following corn harvest so that it can be incorporated into the soil as organic matter and to protect against erosion. Part of the corn stover is oxidized in the atmosphere. Corn stover represents between 40 and 50 per cent of the dry matter (DM) contained in the aerial biomass of corn plants. Recent studies have shown that half of the corn stover could be harvested sustainably on low-sloping land under no-till practice. In Quebec, where 400,000 ha of corn are planted each year, corn stover could provide one million t DM of currently neglected biomass. Various hybrids of corn were monitored from early September to late November at 4 different sites during 2007, 2008 and 2009. Whole plants cut at 100 mm above the ground were collected weekly and separated into 7 fractions, notably the grain, the cob, the husk, the stalk below the ear, the stalk above the ear, the leaves below the ear and the leaves above the ear. In 2007, corn ears on average, were at 0.96 m above the ground at a site with low crop heat units (CHU). Hybrids grown in a warmer site were taller and their ears were 1.21 m above the ground. The DM partitioned in 7 components was 54 per cent grain, 14 per cent bottom stalk, 6 per cent top stalk, 5 per cent bottom leaves, 7 per cent top leaves, 5 per cent husk and 9 per cent cob. The total mass of fibre during harvest decreased from 8.9 to 6.6 t DM/ha for a low CHU hybrid and from 9.3 to 8.3 t DM/ha for a high CHU hybrid. Grain yield increased in 2008 from 3.8 to 7.6 t DM/ha over a 12-week period.
Directory of Open Access Journals (Sweden)
Tao Tao
2014-01-01
Full Text Available A functional carbon nanotube/mesoporous carbon/MnO2 hybrid network has been developed successfully through a facile route. The resulting composites exhibited a high specific capacitance of 351 F/g at 1 A g−1, with intriguing charge/discharge rate performance and cycling stability due to a synergistic combination of large surface area and excellent electron-transport capabilities of MnO2 with the good conductivity of the carbon nanotube/mesoporous carbon networks. Such composite shows great potential to be used as electrodes for supercapacitors.
Hussain, Tanveer; Maark, Tuhina Adit; Pathak, Biswarup; Ahuja, Rajeev
2013-10-01
This study deals with the investigations of structural, electronic and thermodynamic properties of MgH2 doped with selected transition metals (TMs) by means of hybrid density functional theory (PBE0). On the structural side, the calculated lattice parameters and equilibrium volumes increase in case of Sc, Zr and Y opposite to all the other dopants indicating volumetrically increased hydrogen density. Except Fe, all the dopants improve the kinetics of MgH2 by reducing the heat of adsorption with Cu, Nb, Ni and V proving more efficient than others studied TM's. The electronic properties have been studied by density of states and correlated with hydrogen adsorption energies.
Lemal, Sébastien; Varignon, Julien; Bilc, Daniel I.; Ghosez, Philippe
2017-02-01
Using a combination of first-principles calculations based on density functional theory and Boltzmann semiclassical transport theory, we compute and study the properties of pristine layered calcium cobaltite Ca3Co4O9 . We model the system with the B1WC hybrid functional. Two supercells of increasing size which approximate the incommensurate crystallographic structure of the compound are studied and we determine their structural, magnetic, and electronic properties. It is found that the B1WC hybrid functional is appropriate to reproduce the structural, electronic, and magnetic properties, which are then extensively discussed. From the electronic band structure, the Seebeck (S ) and electrical resistivity (ρ ) tensors are computed using Boltzmann transport theory within the constant relaxation-time approximation. The differences between the diagonal components are detailed and reveal a strong in-plane anisotropy of the properties. The qualitative behavior of the averaged in-plane properties, S// and ρ//, is consistent with the measurements reported in the literature. Our calculation clarifies and provides a broad picture of the evolution of the thermoelectric properties with both carrier density and temperature, and suggests that the change in S// and ρ// around 100 K is not necessarily related to the magnetic transitions occurring around 100 K.
Directory of Open Access Journals (Sweden)
Huizheng Ji
2017-01-01
Full Text Available In the background of decreasing fossil fuels and increasing environmental pollution, the wind-photovoltaic energy storage and transmission hybrid power system (or called the wind-PV-ES and transmission hybrid system has become a strategic choice to achieve energy sustainability. However, the comprehensive benefit evaluation of such a combined power system is in a relatively blank state in China, which will hinder the reasonable and orderly development of this station. Four parts, the technical performance, economic benefit, ecological impact and social benefit, are considered in this paper, and a multi-angle evaluation index system of the wind-PV-ES and transmission system is designed. The projection pursuit model is used to evaluated system functionality conventionally; relative entropy theory is used to evaluate the system functionality simultaneously; and a comprehensive benefit evaluation model of the technique for order preference by similar to ideal solution (TOPSIS considering both system functionality and proportionality is constructed. Finally, the national demonstration station of the wind-PV-ES-transmission system is taken as an example to testify to the practicability and validity of the evaluation index system and model.
Patil, Avinash J.; Li, Mei; Mann, Stephen
2013-07-01
Synthesis of functional hybrid nanoscale objects has been a core focus of the rapidly progressing field of nanomaterials science. In particular, there has been significant interest in the integration of evolutionally optimized biological systems such as proteins, DNA, virus particles and cells with functional inorganic building blocks to construct mesoscopic architectures and nanostructured materials. However, in many cases the fragile nature of the biomolecules seriously constrains their potential applications. As a consequence, there is an on-going quest for the development of novel strategies to modulate the thermal and chemical stabilities, and performance of biomolecules under adverse conditions. This feature article highlights new methods of ``inorganic molecular wrapping'' of single or multiple protein molecules, individual double-stranded DNA helices, lipid bilayer vesicles and self-assembled organic dye superstructures using inorganic building blocks to produce bio-inorganic nanoconstructs with core-shell type structures. We show that spatial isolation of the functional biological nanostructures as ``armour-plated'' enzyme molecules or polynucleotide strands not only maintains their intact structure and biochemical properties, but also enables the fabrication of novel hybrid nanomaterials for potential applications in diverse areas of bionanotechnology.
Energy Technology Data Exchange (ETDEWEB)
Lu, Haiyan [Faculty of Engineering and Information Technology, University of Technology, Sydney, Broadway NSW 2007 (Australia); Sriyanyong, Pichet [Department of Teacher Training in Electrical Engineering, Faculty of Technical Education, King Mongkut' s University of Technology, North Bangkok (Thailand); Song, Yong Hua [Department of Electrical Engineering, Tsinghua University (China); Dillon, Tharam [Digital Ecosystems and Business Intelligence Institute, Curtin University of Technology, Western Australia (Australia)
2010-11-15
Particle swarm optimization (PSO) is a population-based evolutionary technique. Advancements in the PSO development over the last decade have made it one of the most promising optimization algorithms for a wide range of complex engineering optimization problems which traditional derivative-based optimization techniques cannot handle. The most attractive features of PSO are its algorithmic simplicity and fast convergence. However, PSO tends to suffer from premature convergence when applied to strongly multi-modal optimization problems. This paper proposes a method of incorporating a real-valued mutation (RVM) operator into the PSO algorithms, aimed at enhancing global search capability. Three variants of PSO algorithms are considered. The resultant hybrid PSO-RVM algorithms are experimentally investigated along with the PSO variants and an existing PSO with Gaussian mutation using six typical benchmark functions. It is interesting to see that the effectiveness of RVM varies for different PSO variants as well as different kinds of functions. It has been found that one of the hybrid algorithms, CBPSO-RVM, which is an integration of the PSO with the constriction factor and inertia weight (CBPSO) and the RVM operator, exhibits significantly better performance in most of the test cases compared to the other algorithms under consideration. Furthermore, this algorithm is superior to most of the existing algorithms used in this study when applied to two practical ED problems with non-smooth cost function considering the multiple fuel type and/or valve-point loading effects. (author)
Xu, Zejing
Silicon nanoparticles are attractive candidates for biological, photovoltaic and energy storage applications due to their size dependent optoelectronic properties. These include tunable light emission, high brightness, and stability against photo-bleaching relative to organic dyes (see Chapter 1). The preparation and characterization of silicon nanoparticle based hybrid nanomaterials and their relevance to photovoltaic and biological applications are described. The surface-passivated silicon nanoparticles were produced in one step from the reactive high-energy ball milling (RHEBM) of silicon wafers with various organic ligands. The surface structure and optical properties of the passivated silicon nanoparticles were systematically characterized. Fast approaches for purifying and at the same time size separating the silicon nanoparticles using a gravity GPC column were developed. The hydrodynamic diameter and size distribution of these size-separated silicon nanoparticles were determined using GPC and Diffusion Ordered NMR Spectroscopy (DOSY) as fast, reliable alternative approaches to TEM. Water soluble silicon nanoparticles were synthesized by grafting PEG polymers onto functionalized silicon nanoparticles with distal alkyne or azide moieties. The surface-functionalized silicon nanoparticles were produced from the reactive high-energy ball milling (RHEBM) of silicon wafers with a mixture of either 5-chloro-1-pentyne in 1-pentyne or 1,7 octadiyne in 1-hexyne to afford air and water stable chloroalkyl or alkynyl terminated nanoparticles, respectively. Nanoparticles with the ω-chloroalkyl substituents were easily converted to ω-azidoalkyl groups through the reaction of the silicon nanoparticles with sodium azide in DMF. The azido terminated nanoparticles were then grafted with monoalkynyl-PEG polymers using a copper catalyzed alkyne-azide cycloaddition (CuAAC) reaction to afford core-shell silicon nanoparticles with a covalently attached PEG shell. Covalently
Abhilash, Kochukunju Adisser Saraladevi; Deepthi, Thomas; Sadhana, Retnakumari Amma; Benny, K George
2015-08-19
Functionalized polysilsesquioxane-based hybrid silica materials are presented as solid amine sorbents for direct CO2 capture from air. The sorbent was synthesized from amine and vinyl functionalized alkoxysilanes by a simple, energy efficient, and cost-effective co-condensation method. The material, containing bound amine functionalities, was found to have a selective CO2 capturing capacity of 1.68 mmol/g from atmospheric air with an adsorption half time of 50 min. This material also showed a maximum adsorption capacity of 2.28 mmol/g in pure CO2 and 1.92 mmol/g in 10% CO2. Desorption started at a temperature as low as 60 °C, and complete desorption occurred at 80 °C. The sorbent exhibited high recycling ability, and 100 cycles of adsorption/desorption were demonstrated in pure CO2 and 50 cycles in ambient air without any loss in efficiency.
Mohammadpour, Mozhdeh; Jamshidi, Zahra
2016-05-01
The prospect of challenges in reproducing and interpretation of resonance Raman properties of molecules interacting with metal clusters has prompted the present research initiative. Resonance Raman spectra based on the time-dependent gradient approximation are examined in the framework of density functional theory using different methods for representing the exchange-correlation functional. In this work the performance of different XC functionals in the prediction of ground state properties, excitation state energies, and gradients are compared and discussed. Resonance Raman properties based on time-dependent gradient approximation for the strongly low-lying charge transfer states are calculated and compared for different methods. We draw the following conclusions: (1) for calculating the binding energy and ground state geometry, dispersion-corrected functionals give the best performance in comparison to ab initio calculations, (2) GGA and meta GGA functionals give good accuracy in calculating vibrational frequencies, (3) excited state energies determined by hybrid and range-separated hybrid functionals are in good agreement with EOM-CCSD calculations, and (4) in calculating resonance Raman properties GGA functionals give good and reasonable performance in comparison to the experiment; however, calculating the excited state gradient by using the hybrid functional on the hessian of GGA improves the results of the hybrid functional significantly. Finally, we conclude that the agreement of charge-transfer surface enhanced resonance Raman spectra with experiment is improved significantly by using the excited state gradient approximation.
Kitt, Jay P; Harris, Joel M
2016-09-01
Measuring lipid-membrane partitioning of small molecules is critical to predicting bioavailability and investigating molecule-membrane interactions. A stable model membrane for such studies has been developed through assembly of a phospholipid monolayer on n-alkane-modified surfaces. These hybrid bilayers have recently been generated within n-alkyl-chain (C18)-modified porous silica and used in chromatographic retention studies of small molecules. Despite their successful application, determining the structure of hybrid bilayers within chromatographic silica is challenging because they reside at buried interfaces within the porous structure. In this work, we employ confocal Raman microscopy to investigate the formation and temperature-dependent structure of hybrid-phospholipid bilayers in C18-modified, porous-silica chromatographic particles. Porous silica provides sufficient surface area within a confocal probe volume centered in an individual particle to readily measure, with Raman microscopy, the formation of an ordered hybrid bilayer of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) with the surface C18 chains. The DMPC surface density was quantified from the relative Raman scattering intensities of C18 and phospholipid acyl chains and found to be ∼40% of a DMPC vesicle membrane. By monitoring Raman spectra acquired versus temperature, the bilayer main phase transition was observed to be broadened and shifted to higher temperature compared to a DMPC vesicle, in agreement with differential scanning calorimetry (DSC) results. Raman scattering of deuterated phospholipid was resolved from protonated C18 chain scattering, showing that the lipid acyl and C18 chains melt simultaneously in a single phase transition. The surface density of lipid in the hybrid bilayer, the ordering of both C18 and lipid acyl chains upon bilayer formation, and decoupling of C18 methylene C-H vibrations by deuterated lipid acyl chains all suggest an interdigitated acyl chain
Khiterer, Mariya
2007-05-01
This dissertation describes the design, fabrication, and characterization of organic-inorganic hybrid materials. Several classes of bridged polysilsesquioxanes are presented. The first class is a membrane material suitable for fuel cell technology as a proton conducting polyelectrolyte. The second class includes hybrid nanoparticles for display device applications and chromatographic media. Chapter 1 is an introduction to hybrid organic-inorganic materials. Sol-gel chemistry is discussed, followed by a survey of prominent examples of silica hybrids. Examples of physical organic-silica blends and covalent organo-silicas, including ORMOCERSRTM, polyhedral oligomeric silsesquioxanes, and bridged polysilsesquioxanes are discussed. Bridged polysilsesquioxanes are described in great detail. Monomer synthesis, sol-gel chemistry, processing, characterization, and physical properties are included. Chapter 2 describes the design of polyelectrolyte bridged polysilsesquioxane membranes. The materials contain covalently bound sulfonic acid groups originating from the corresponding disulfides. These organic-inorganic hybrid materials integrate a network supporting component which is systematically changed to fine-tune their physical properties. The membranes are characterized as PEM fuel cell electrolytes, where proton conductivities of 4-6 mS cm-1 were measured. In Chapter 3 techniques for the preparation of bridged polysilsesquioxane nanoparticles are described. An inverse water-in-oil microemulsion polymerization method is developed to prepare cationic nanoparticles, including viologen-bridged materials with applications in electrochromic display devices. An aqueous ammonia system is used to prepare neutral nanoparticles containing hydrocarbon bridging groups, which have potential applications as chromatographic media. Chapter 4 describes electrochromic devices developed in collaboration with the Heflin group of Virginia Tech, which incorporate viologen bridged nanoparticles
Huang, Wei; Oh, Sung-Kwun; Pedrycz, Witold
2014-12-01
In this study, we propose Hybrid Radial Basis Function Neural Networks (HRBFNNs) realized with the aid of fuzzy clustering method (Fuzzy C-Means, FCM) and polynomial neural networks. Fuzzy clustering used to form information granulation is employed to overcome a possible curse of dimensionality, while the polynomial neural network is utilized to build local models. Furthermore, genetic algorithm (GA) is exploited here to optimize the essential design parameters of the model (including fuzzification coefficient, the number of input polynomial fuzzy neurons (PFNs), and a collection of the specific subset of input PFNs) of the network. To reduce dimensionality of the input space, principal component analysis (PCA) is considered as a sound preprocessing vehicle. The performance of the HRBFNNs is quantified through a series of experiments, in which we use several modeling benchmarks of different levels of complexity (different number of input variables and the number of available data). A comparative analysis reveals that the proposed HRBFNNs exhibit higher accuracy in comparison to the accuracy produced by some models reported previously in the literature.
Raman signatures of strong Kitaev exchange correlations in (Na1-xLix)2IrO3: Experiments and theory
Nath Gupta, Satyendra; Sriluckshmy, P. V.; Mehlawat, Kavita; Balodhi, Ashiwini; Mishra, Dileep K.; Hassan, S. R.; Ramakrishnan, T. V.; Muthu, D. V. S.; Singh, Yogesh; Sood, A. K.
2016-05-01
Inelastic light scattering studies on single crystals of (Na1-x Li x )2IrO3 (x = 0, 0.05 and 0.15) show a polarization-independent broad band at ˜ 2750 cm-1 with a large band-width ˜ 1800 \\text{cm}-1 . For Na2IrO3 the broad band is seen for temperatures ≤ 200 \\text{K} and persists inside the magnetically ordered state. For Li samples, the intensity of this mode increases, shifts to lower wave numbers, and persists to higher temperatures. Such a mode has recently been predicted (by Knolle et al.) as a signature of the Kitaev spin liquid. We assign the observation of the broad band to be a signature of strong Kitaev exchange correlations. The fact that the broad band persists even inside the magnetically ordered state suggests that dynamically fluctuating moments survive even below T N . This is further supported by our mean-field calculations. The Raman response calculated in mean-field theory shows that the broad band predicted for the SL state survives in the magnetically ordered state near the zigzag-spin liquid phase boundary. A comparison with the theoretical model gives an estimate of the Kitaev exchange interaction parameter to be J_K≈ 57 \\text{meV} .
Alcaire Martín, María
2015-01-01
In general, functional materials are categorized as those materials which possess particular native properties and functions of their own. Examples of these properties are: ferroelectricity, piezoelectricity, magnetism, temperature variations, pressure variations and optical functions. There exists an immense range of functional materials. For instance, optical materials, including lasers, Raman scattering, fluorescence and phosphorescence, are functional materials. Moreover, electrical, magn...
Petretto, Guido; Bruneval, Fabien
2015-12-01
The identification of defect levels from photoluminescence spectroscopy is a useful but challenging task. Density-functional theory (DFT) is a highly valuable tool to this aim. However, the semilocal approximations of DFT that are affected by a band gap underestimation are not reliable to evaluate defect properties, such as charge transition levels. It is now established that hybrid functional approximations to DFT improve the defect description in semiconductors. Here we demonstrate that the use of hybrid functionals systematically stabilizes donor defect states in the lower part of the band gap for many defects, impurities or vacancies, in III-V and in II-VI semiconductors, even though these defects are usually considered as acceptors. These donor defect states are a very general feature and, to the best of our knowledge, have been overlooked in previous studies. The states we identify here may challenge the older assignments to photoluminescent peaks. Though appealing to screen quickly through the possible stable charge states of a defect, semilocal approximations should not be trusted for that purpose.
A Hybrid Knowledge-Based and Empirical Scoring Function for Protein-Ligand Interaction: SMoG2016.
Debroise, Théau; Shakhnovich, Eugene I; Chéron, Nicolas
2017-03-27
We present the third generation of our scoring function for the prediction of protein-ligand binding free energy. This function is now a hybrid between a knowledge-based potential and an empirical function. We constructed a diversified set of ∼1000 complexes from the PDBBinding-CN database for the training of the function, and we show that this number of complexes generates enough data to build the potential. The occurrence of 420 different types of atomic pairwise interactions is computed in up to five different ranges of distances to derive the knowledge-based part. All of the parameters were optimized, and we were able to considerably improve the accuracy of the scoring function with a Pearson correlation coefficient against experimental binding free energies of up to 0.57, which ranks our new scoring function as one of the best currently available and the second-best in terms of standard deviation (SD = 1.68 kcal/mol). The function was then further improved by inclusion of different terms taking into account repulsion and loss of entropy upon binding, and we show that it is capable of recovering native binding poses up to 80% of the time. All of the programs, tools, and protein sets are released in the Supporting Information or as open-source programs.
Directory of Open Access Journals (Sweden)
Hahnbeom Park
Full Text Available Protein loop modeling is a tool for predicting protein local structures of particular interest, providing opportunities for applications involving protein structure prediction and de novo protein design. Until recently, the majority of loop modeling methods have been developed and tested by reconstructing loops in frameworks of experimentally resolved structures. In many practical applications, however, the protein loops to be modeled are located in inaccurate structural environments. These include loops in model structures, low-resolution experimental structures, or experimental structures of different functional forms. Accordingly, discrepancies in the accuracy of the structural environment assumed in development of the method and that in practical applications present additional challenges to modern loop modeling methods. This study demonstrates a new strategy for employing a hybrid energy function combining physics-based and knowledge-based components to help tackle this challenge. The hybrid energy function is designed to combine the strengths of each energy component, simultaneously maintaining accurate loop structure prediction in a high-resolution framework structure and tolerating minor environmental errors in low-resolution structures. A loop modeling method based on global optimization of this new energy function is tested on loop targets situated in different levels of environmental errors, ranging from experimental structures to structures perturbed in backbone as well as side chains and template-based model structures. The new method performs comparably to force field-based approaches in loop reconstruction in crystal structures and better in loop prediction in inaccurate framework structures. This result suggests that higher-accuracy predictions would be possible for a broader range of applications. The web server for this method is available at http://galaxy.seoklab.org/loop with the PS2 option for the scoring function.
Mo, Chongjie; Yang, Yu; Kang, Wei; Zhang, Ping
2016-04-01
The electronic structure and optical properties for the (U,Th)O2 compound are systematically studied by employing the Heyd-Scuseria-Ernzerh method (HSE) of screened hybrid density functional. The electronic band gap of (U,Th)O2 is predicted to be 3.06 eV, in the middle of the values of UO2 and ThO2. Based on wavefunction analysis, we conclude (U,Th)O2 to be a Mott insulator in its ground state. The frequency dependent dielectric functions and optical properties are then calculated and compared with those of ThO2 and UO2. At the visible light frequency range, the adsorption coefficients for ThO2, UO2 and (U,Th)O2 are totally different, which gives an accessible method to predict the proportion of U atoms in an arbitrary unknown (U,Th)O2 compounds from the adsorption spectrum of visible lights.
Energy Technology Data Exchange (ETDEWEB)
AbouZeid, Khaled Mohamed [Virginia Commonwealth University, Department of Chemistry (United States); Mohamed, Mona Bakr [Cairo University, National Institute of Laser Enhanced Science (NILES) (Egypt); El-Shall, M. Samy, E-mail: mselshal@vcu.edu [Virginia Commonwealth University, Department of Chemistry (United States)
2016-01-15
This work introduces a series of molecular bridging bi-functional linkers to produce laterally self-assembled nanostructures of the Au–CdSe nanoflowers on different length scales ranging from 10 nm to 100 microns. Assembly of Au nanocrystals within amorphous CdSe rods is found in the early stages of the growth of the Au–CdSe nanoflowers. The Au–CdSe nanoflowers are formed through a one-pot low temperature (150 °C) process where CdSe clusters are adsorbed on the surface of the Au cores, and they then start to form multiple arms and branches resulting in flower-shaped hybrid nanostructures. More complex assembly at a micron length scale can be achieved by means of bi-functional capping agents with appropriate alkyl chain lengths, such as 1,12-diaminododecane.
Zheng, Ming-Ming; Ruan, Ge-Deng; Feng, Yu-Qi
2009-11-06
A hybrid organic-inorganic silica monolith with hydrophobic and strong cation-exchange functional groups was prepared and used as a sorbent for micro-solid phase extraction (micro-SPE). The hybrid silica monolith functionalized with octyl and thiol groups was conveniently synthesized by hydrolysis and polycondensation of a mixture of tetraethoxysilane (TEOS), n-octyltriethoxysilane (C8-TEOS) and 3-mercaptopropyltrimethoxysilane (MPTMS) via a two-step catalytic sol-gel process. Due to the favorable chemical reactivity of mercapto pendant moieties, the obtained hybrid monolith was oxidized using hydrogen peroxide (30%, w/w) to yield sulfonic acid groups, which provided strong cation-exchange sites. The obtained hybrid monolith was characterized by diffused infrared spectroscopy, elemental analysis, scanning electron microscopy and mercury intrusion porosimetry. The results show that the resulting monolith contains much higher carbon (31.6%) and sulfur (4.8%) contents than traditionally bonded silica materials. The extraction performance of the hybrid monolith was evaluated using sulfonamides as testing analytes by micro-SPE on-line coupled to HPLC. The results show that the hybrid monolith with hydrophobic and strong cation-exchange functional groups exhibits high extraction efficiency towards the testing analytes. The column-to-column RSD values were 1.3-9.8% for the extraction of SAs investigated. The extraction performance of the hybrid silica monolith remained practically unchanged after treated with acid (pH 1.0) and basic solutions (pH 10.5). Finally, the application of the hybrid monolith was demonstrated by micro-SPE of sulfonamide residues from milk followed by HPLC-UV analysis. The limits of detection (S/N=3) for eight SAs were found to be 1.0-3.0ng/mL in milk. The recoveries of eight SAs spiked in milk sample ranged from 80.2% to 115.6%, with relative standard deviations less than 11.8%.
Cho, Seulki; Kim, Nahae; Lee, Soonjae; Lee, Hoseok; Lee, Sang-Hyup; Kim, Juyoung; Choi, Jae-Woo
2016-08-01
In this study, we present new inorganic-organic hybrid particles and their possible application as an adsorbent for simultaneous removal of hydrophobic and hydrophilic pollutants from water. These hybrid particles were prepared using tailor-made alkoxysilane-functionalized amphiphilic polymer precursors (M-APAS), which have amphiphilic polymers and reactive alkoxysilane groups attached to the same backbone. Through a single conventional sol-gel process, the polymerization of M-APAS and the chemical conjugation of M-APAS onto silica nanoparticles was simultaneous, resulting in the formation of hybrid particles (M-APAS-SiO2) comprised of hyperbranch-like amphiphilic polymers bonded onto silica nanoparticles with a relatively high grafting efficiency. A test for the adsorption of water-soluble dye (organe-16) and water insoluble dye (solvent blue-35) onto the hybrid particles was performed to evaluate the possibility of adsorbing hydrophilic and hydrophobic compound within the same particle. The hybrid particle was also evaluated as an adsorbent for the removal of contaminated water containing various pollutants by wastewater treatment test. The hybrid particle could remove phenolic compounds from wastewater and the azo dye reactive orange-16 from aqueous solutions, and it was easily separated from the treated wastewater because of the different densities involved. These results demonstrate that the hybrid particles are a promising sorbent for hydrophilic and/or hydrophobic pollutants in water.
Zhao, Lingzhou; Mei, Shenglin; Chu, Paul K; Zhang, Yumei; Wu, Zhifen
2010-07-01
Hierarchical hybrid micro/nano-textured titanium surface topographies with titania nanotubes were produced by simple acid etching followed by anodization to mimic the hierarchical structure of bone tissues. Primary rat osteoblasts were used to evaluate the bioactivity. The microtopography formed by acid etching of titanium induced inconsistent osteoblast functions with initial cell adhesion and osteogenesis-related gene expression being dramatically enhanced while other cell behaviors such as proliferation, intracellular total protein synthesis and alkaline phosphatase activity, collagen secretion, and extracellular matrix mineralization being depressed. In comparison, addition of nanotubes to the microtopography led to enhancement of multiple osteoblast functions. Nearly all the cell functions investigated in this study were retained or promoted. Compared to a microtopography, the enhancement of multiple cell functions observed from the hierarchical micro/nano-textured surfaces is expected to lead to faster bone maturation around the titanium implants without compromising the bone mass. In addition, the hierarchical micro/nano-textured surfaces still retain the mechanical interlocking ability of the microtopography thereby boding well for osseointegration. Our study reveals a synergistic role played by the micro and nanotopographies in osteoblast functions and provides insight to the design of better biomedical implant surfaces.
Li, Guixin; Yu, Xiuxia; Liu, Danqing; Liu, Xiaoying; Li, Fang; Cui, Hua
2015-11-03
The electrochemiluminescence (ECL) behavior of N-(aminobutyl)-N-(ethylisoluminol)/hemin dual-functionalized graphene hybrids (A-H-GNs) and luminol-functionalized silver/graphene oxide composite (luminol-AgNPs-GO) was investigated under cyclic voltammetry and pulse potential. It was found that A-H-GNs and luminol-AgNPs-GO exhibited excellent ECL activity. On this basis, a label-free ECL aptasensor for 2,4,6-trinitrotoluene (TNT) detection was developed based on bilayer structure of luminescence functionalized graphene hybrids consisting of A-H-GNs and luminol-AgNPs-GO. First, positively charged chitosan-coated A-H-GNs were modified on the surface of indium-doped tin oxide electrode by simple dripping and drying in the air; after that, the modified electrode was immersed in negatively charged luminol-AgNPs-GO modified with aptamer (apta-biotin-SA-luminol-AgNPs-GO) to form apta-biotin-SA-luminol-AgNPs-GO/CS-A-H-GNs/ITO electrode (i.e., aptasensor) by electrostatic interaction. In the presence of TNT, a remarkable decrease in ECL signals was observed due to the formation of aptamer-TNT complex. TNT could be detected based on the inhibition effect. The aptasensor exhibits a wide dynamic range from 1.0 × 10(-12) to 1.0 × 10(-9) g/mL, with a low detection limit of 6.3 × 10(-13) g/mL for the determination of TNT, which is superior to most previously reported bioassays for TNT. Moreover, the proposed aptasensor has been successfully applied to the detection of TNT in environmental water. It is sensitive, selective, and simple, avoiding complicated labeling and purification procedures. Due to the wide target recognition range of aptamer, this strategy provides a promising way to develop new aptasensor for other analytes.
Cunha, C.; Panseri, S.; Iannazzo, D.; Piperno, A.; Pistone, A.; Fazio, M.; Russo, A.; Marcacci, M.; Galvagno, S.
2012-11-01
A straightforward technique for functionalization of multiwalled carbon nanotubes (MWCNTs) with magnetite (Fe3O4) nanoparticles was developed. Iron oxide nanoparticles were deposited on MWCNT surfaces by a deposition-precipitation method using Fe3+/Fe2+ salts precursors in basic solution. The characterizations by HRTEM, XRD, SEM/EDX, AAS and TPR analyses confirmed the successful formation of magnetic iron oxide nanoparticles on the MWCNT surface. Fe3O4/MWCNT hybrid composites were analysed in vitro by incubation with mesenchymal stem cells for 1, 3 and 7 days, either in the presence or absence of a static magnetic field. Analysis of cell proliferation was performed by the MTT assay, quantification of cellular stress was performed by the Lactate Dehydrogenase assay and analysis of cell morphology was performed by actin immunofluorescence and scanning electron microscopy. Results demonstrate that the introduction of magnetite into the MWCNT structure increases biocompatibility of oxidized MWCNTs. In addition, the presence of a static magnetic field further increases Fe3O4/MWCNT influence on cell behaviour. These results demonstrate this novel Fe3O4/MWCNT hybrid composite has good potential for tissue engineering applications.
Energy Technology Data Exchange (ETDEWEB)
Hopkins, M.B. (Dublin City Univ. (Ireland). Dept. of Physics); Bacal, M. (Ecole Polytechnique, 91 - Palaiseau (France). Lab. de Physique des Milieux Ionises); Graham, W.G. (Queen' s Univ., Belfast, Northern Ireland (UK). School of Mathematics and Physics)
1991-03-14
The second derivative of a Langmuir probe characteristic is used to establish the electron energy distribution function (EEDF) in both a tandem and hybrid multicusp H{sup -} ion source. Moveable probes are used to establish the spatial variation of the EEDF. The negative ion density is measured by laser induced photo-detachment. In the case of the hybrid source the EEDF consists of a cold Maxwellian in the central region of the source; the electron temperature increases with increasing discharge current (rising from 0.3 eV at 1 A to 1.2 eV at 50 A when the pressure is 0.4 Pa). A hot electron tail exists in the EEDF of the driver region adjacent to each filament which is shown to consist of a distinct group of primary electrons at low pressure (0.08 Pa) but becomes degraded mainly through inelastic collisions at higher pressures (0.27 Pa). The tandem source, on the other hand, has a single driver region which extends throughout the central region. The primary electron confinement times are much longer so that even at the lowest pressure considered (0.07 Pa) the primaries are degraded. In both cases the measured EEDF at specific locations and values of discharge operating parameters are used to establish the rate coefficients for the processes of importance in H{sup -} production and destruction. (author).
Wang, Jing; Wang, Yuanming; Zhang, Yatao; Uliana, Adam; Zhu, Junyong; Liu, Jindun; Van der Bruggen, Bart
2016-09-28
Inspired by the rational design concept, a novel antimicrobial agent zeolitic imidazolate framework-8 (ZIF-8)/graphene oxide (GO) was synthesized and utilized as a novel and efficient bactericidal agent to fabricate antimicrobial thin film nanocomposite (TFN) membranes via interfacial polymerization. The resultant hybrid nanosheets not only integrates the merits of both ZIF-8 and GO but also yields a uniform dispersion of ZIF-8 onto GO nanosheets simultaneously, thus effectively eliminating the agglomeration of ZIF-8 in the active layer of membranes. A ZIF-8/GO thin film nanocomposite (TFN-ZG) membrane with typical water permeability (40.63 L m(-2) h(-1) MPa(-1)) allows for efficient bivalent salt removal (rejections of Na2SO4 and MgSO4 were 100% and 77%, respectively). Furthermore, the synthesized ZIF-8/GO nanocomposites were verified to have an optimal antimicrobial activity (MIC,128 μg/mL) in comparison with ZIF-8 and GO separately, which sufficiently endowed the TFN-ZG membrane with excellent antimicrobial activity (84.3% for TFN-ZG3). Besides, the antimicrobial mechanisms of ZIF-8/GO hybrid nanosheets and TFN-ZG membranes were proposed. ZIF-8/GO functionalized membrane with high antimicrobial activity and salt retention denoted its great potential in water desalination, and we suggest that ZIF-8 based crystal may offer a new pathway for the synthesis of a multifunctional bactericide.
Directory of Open Access Journals (Sweden)
Li Ying
2010-01-01
Full Text Available Abstract Novel organic–inorganic mesoporous luminescent hybrid material N, N′-bis(salicylidene-thiocarbohydrazide (BSTC-SBA-15 has been obtained by co-condensation of tetraethyl orthosilicate and the organosilane in the presence of Pluronic P123 surfactant as a template. N,N′-bis(salicylidene-thiocarbohydrazide (BSTC grafted to the coupling agent 3-(triethoxysilyl-propyl isocyanate (TESPIC was used as the precursor for the preparation of mesoporous materials. In addition, for comparison, SBA-15 doped with organic ligand BSTC was also synthesized, denoted as BSTC/SBA-15. This organic–inorganic hybrid material was well-characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy (HRTEM, and photoluminescence spectra, which reveals that they all have high surface area, uniformity in the mesostructure. The resulting materials (BSTC-SBA-15 and BSTC/SBA-15 exhibit regular uniform microstructures, and no phase separation happened for the organic and the inorganic compounds was covalently linked through Si–O bonds via a self-assemble process. Furthermore, the two materials have different luminescence range: BSTC/SBA-15 presents the strong dominant green luminescence, while BSTC-functionalized material BSTC-SBA-15 shows the dominant blue emission.
Nishihara, S.; Otani, M.
2017-09-01
We present two hybrid solvation models for the calculation of the solvation structure with model 1 in a confined nanospace in bulk materials and model 2 at solid/liquid interfaces where an electrode is in contact with an electrolyte and a membrane is immersed into a solution. The hybrid theory is based on the reference interaction site method (RISM) for the solvent region. The electronic structure of a bulk material, an electrode, and a membrane is treated by density functional theory with the plane-wave basis and pseudopotentials technique. For model 1, we use the three-dimensional RISM (3D-RISM) by imposing a 3D periodic boundary condition on the system. However, for model 2, we reformulate the RISM by means of a two-dimensional boundary condition parallel to the surface and an open boundary condition normal to the surface. Four benchmark calculations are performed for the formaldehyde-water system, water packed into a zeolite framework, a NaCl solution in contact with an Al electrode, and an Al thin film immersed in a NaCl solution with different concentrations. The calculations are shown to be efficient and stable. Because of the flexibility of the RISM theory, the models are considered to be applicable to a wide range of solid/liquid interfaces.
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Lhassane Idoumghar
2011-01-01
When a local optimal solution is reached with PSO, all particles gather around it, and escaping from this local optima becomes difficult. To avoid premature convergence of PSO, we present a new hybrid evolutionary algorithm, called HPSO-SA, based on the idea that PSO ensures fast convergence, while SA brings the search out of local optima because of its strong local-search ability. The proposed HPSO-SA algorithm is validated on ten standard benchmark multimodal functions for which we obtained significant improvements. The results are compared with these obtained by existing hybrid PSO-SA algorithms. In this paper, we provide also two versions of HPSO-SA (sequential and distributed for minimizing the energy consumption in embedded systems memories. The two versions, of HPSO-SA, reduce the energy consumption in memories from 76% up to 98% as compared to Tabu Search (TS. Moreover, the distributed version of HPSO-SA provides execution time saving of about 73% up to 84% on a cluster of 4 PCs.
Sun, Lili; Wan, Kun; Hu, Xueyuan; Zhang, Yonghong; Yan, Zijun; Feng, Jiao; Zhang, Jingqing
2016-02-01
The purpose of this study was to assess the enhanced physicochemical characteristics, in vitro release behavior, anti-lung cancer activity, gastrointestinal absorption, in vivo bioavailability and bioequivalence of functional nanoemulsion-hybrid lipid nanocarriers containing diferuloylmethane (DNHLNs). The DNHLNs were first fabricated by loading water-in-oil nanoemulsions into hybrid lipid nanosystems using nanoemulsion-thin film-sonication dispersion technologies. The in situ absorption and in vitro and in vivo kinetic features of DNHLNs were measured using an in situ unidirectional perfusion method, a dynamic dialysis method and a plasma concentration-time profile-based method, respectively. The cytotoxic effects of DNHLNs in lung adenocarcinoma A549 cells were examined using MTT colorimetric analysis. The absorptive constants and permeabilities of DNHLNs in four gastrointestinal sections increased by 1.43-3.23 times and by 3.10-7.76 times that of diferuloylmethane (DIF), respectively. The relative bioavailability of DNHLNs to free DIF was 855.02%. DNHLNs inhibited cancer cell growth in a time- and dose-dependent manner. DNHLNs markedly improved the absorption and bioavailability of DIF after oral administration. DNHLNs had stronger inhibitory effects on the viability of A549 cells than that of free DIF. DNHLNs might be potentially promising nanocarriers for DIF delivery via the oral route to address unmet clinical needs.
Weber, Valéry; Tymczak, Christopher J; Challacombe, Matt
2006-06-14
The application of theoretical methods based on density-functional theory is known to provide atomic and cell parameters in very good agreement with experimental values. Recently, construction of the exact Hartree-Fock exchange gradients with respect to atomic positions and cell parameters within the Gamma-point approximation has been introduced. In this article, the formalism is extended to the evaluation of analytical Gamma-point density-functional atomic and cell gradients. The infinite Coulomb summation is solved with an effective periodic summation of multipole tensors. While the evaluation of Coulomb and exchange-correlation gradients with respect to atomic positions are similar to those in the gas phase limit, the gradients with respect to cell parameters needs to be treated with some care. The derivative of the periodic multipole interaction tensor needs to be carefully handled in both direct and reciprocal space and the exchange-correlation energy derivative leads to a surface term that has its origin in derivatives of the integration limits that depend on the cell. As an illustration, the analytical gradients have been used in conjunction with the QUICCA algorithm to optimize one-dimensional and three-dimensional periodic systems at the density-functional theory and hybrid Hartree-Fock/density-functional theory levels. We also report the full relaxation of forsterite supercells at the B3LYP level of theory.
Institute of Scientific and Technical Information of China (English)
S. Asaoka
2005-01-01
@@ 1Introduction: What are resin catalyst hybrids? There are typically two types of resin catalyst. One is acidic resin which representative is polystyrene sulfonic acid. The other is basic resin which is availed as metal complex support. The objective items of this study on resin catalyst are consisting of pellet hybrid, equilibrium hybrid and function hybrid of acid and base,as shown in Fig. 1[1-5].
Directory of Open Access Journals (Sweden)
Falko Schmidt
2017-01-01
Full Text Available We perform a comprehensive theoretical study of the structural and electronic properties of potassium niobate (KNbO3 in the cubic, tetragonal, orthorhombic, monoclinic, and rhombohedral phase, based on density-functional theory. The influence of different parametrizations of the exchange-correlation functional on the investigated properties is analyzed in detail, and the results are compared to available experimental data. We argue that the PBEsol and AM05 generalized gradient approximations as well as the RTPSS meta-generalized gradient approximation yield consistently accurate structural data for both the external and internal degrees of freedom and are overall superior to the local-density approximation or other conventional generalized gradient approximations for the structural characterization of KNbO3. Band-structure calculations using a HSE-type hybrid functional further indicate significant near degeneracies of band-edge states in all phases which are expected to be relevant for the optical response of the material.
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.
Krishnamurthy, Srini; Van Orden, Derek; Yu, Zhi-Gang
2016-09-01
We have developed a hybrid method that can be applied to study isolated defects in semiconductor compounds and superlattices. The method is a combination of (1) a long-range tight-binding (TB) Hamiltonian, (2) a first-principles Hamiltonian, and (3) a Green's function (GF) formalism. The calculation of the GF requires accurate energy band structure, wave functions, and defect potentials. The TB Hamiltonian with sp 3 orbitals basis ensures accurate band gaps and band masses while providing the functional form for the wave functions. We calculated the band gaps of InAs/GaSb and InAs/InAsSb strained-layer superlattices and found them to agree well with measurements. The change in potentials caused by native point defects (NPDs) was obtained from a first-principles method using Spanish Initiative for Electronic Simulations with Thousands of Atoms, which also uses sp 3 basis. We describe the method of calculating NPD energy levels in compounds and superlattices, obtain some defect levels in GaAs, InAs, InSb, and GaSb compounds, and provide details of the NPD-level calculations.
Quang, Daniel; Xie, Xiaohui
2016-06-20
Modeling the properties and functions of DNA sequences is an important, but challenging task in the broad field of genomics. This task is particularly difficult for non-coding DNA, the vast majority of which is still poorly understood in terms of function. A powerful predictive model for the function of non-coding DNA can have enormous benefit for both basic science and translational research because over 98% of the human genome is non-coding and 93% of disease-associated variants lie in these regions. To address this need, we propose DanQ, a novel hybrid convolutional and bi-directional long short-term memory recurrent neural network framework for predicting non-coding function de novo from sequence. In the DanQ model, the convolution layer captures regulatory motifs, while the recurrent layer captures long-term dependencies between the motifs in order to learn a regulatory 'grammar' to improve predictions. DanQ improves considerably upon other models across several metrics. For some regulatory markers, DanQ can achieve over a 50% relative improvement in the area under the precision-recall curve metric compared to related models. We have made the source code available at the github repository http://github.com/uci-cbcl/DanQ.
Li, Yan; Calder, Steven; Yaffe, Omer; Cahen, David; Haick, Hossam; Kronik, Leeor; Zuilhof, Han
2012-07-03
Since the first report of Si-C bound organic monolayers on oxide-free Si almost two decades ago, a substantial amount of research has focused on studying the fundamental mechanical and electronic properties of these Si/molecule surfaces and interfaces. This feature article covers three closely related topics, including recent advances in achieving high-density organic monolayers (i.e., atomic coverage >55%) on oxide-free Si(111) substrates, an overview of progress in the fundamental understanding of the energetics and electronic properties of hybrid Si/molecule systems, and a brief summary of recent examples of subsequent functionalization on these high-density monolayers, which can significantly expand the range of applicability. Taken together, these topics provide an overview of the present status of this active area of research.
Directory of Open Access Journals (Sweden)
Tanveer Hussain
2013-10-01
Full Text Available This study deals with the investigations of structural, electronic and thermodynamic properties of MgH2 doped with selected transition metals (TMs by means of hybrid density functional theory (PBE0. On the structural side, the calculated lattice parameters and equilibrium volumes increase in case of Sc, Zr and Y opposite to all the other dopants indicating volumetrically increased hydrogen density. Except Fe, all the dopants improve the kinetics of MgH2 by reducing the heat of adsorption with Cu, Nb, Ni and V proving more efficient than others studied TM’s. The electronic properties have been studied by density of states and correlated with hydrogen adsorption energies.
Yoosefian, Mehdi; Etminan, Nazanin
2016-07-01
In order to explore a new novel L-amino acid/transition metal doped single walled carbon nanotube based biosensor, density functional theory calculations were studied. These hybrid structures of organic-inorganic nanobiosensors are able to detect the smallest amino acid building block of proteins. The configurations of amine and carbonyl group coordination of tryptophan aromatic amino acid adsorbed on Pd/doped single walled carbon nanotube were compared. The frontier molecular orbital theory, quantum theory atom in molecule and natural bond orbital analysis were performed. The molecular electrostatic potential and the electron density surfaces were constructed. The calculations indicated that the Pd/SWCNT was sensitive to tryptophan suggesting the importance of interaction with biological molecule and potential detecting application. The proposed nanobiosensor represents a highly sensitive detection of protein at ultra-low concentration in diagnosis applications.
Directory of Open Access Journals (Sweden)
Yu-Chieh Wu
Full Text Available BACKGROUND: Type I insulin-like growth factor receptor (IGF-1R and insulin receptor (INSR are highly homologous molecules, which can heterodimerize to form an IGF-1R/INSR hybrid (Hybrid-R. The presence and biological significance of the Hybrid-R in human corneal epithelium has not yet been established. In addition, while nuclear localization of IGF-1R was recently reported in cancer cells and human corneal epithelial cells, the function and profile of nuclear IGF-1R is unknown. In this study, we characterized the nuclear localization and function of the Hybrid-R and the role of IGF-1/IGF-1R and Hybrid-R signaling in the human corneal epithelium. METHODOLOGY/PRINCIPLE FINDINGS: IGF-1-mediated signaling and cell growth were examined in a human telomerized corneal epithelial (hTCEpi cell line using co-immunoprecipitation, immunoblotting and cell proliferation assays. The presence of Hybrid-R in hTCEpi and primary cultured human corneal epithelial cells was confirmed by immunofluorescence and reciprocal immunoprecipitation of whole cell lysates. We found that IGF-1 stimulated Akt and promoted cell growth through IGF-1R activation, which was independent of the Hybrid-R. The presence of Hybrid-R, but not IGF-1R/IGF-1R, was detected in nuclear extracts. Knockdown of INSR by small interfering RNA resulted in depletion of the INSR/INSR and preferential formation of Hybrid-R. Chromatin-immunoprecipitation sequencing assay with anti-IGF-1R or anti-INSR was subsequently performed to identify potential genomic targets responsible for critical homeostatic regulatory pathways. CONCLUSION/SIGNIFICANCE: In contrast to previous reports on nuclear localized IGF-1R, this is the first report identifying the nuclear localization of Hybrid-R in an epithelial cell line. The identification of a nuclear Hybrid-R and novel genomic targets suggests that IGF-1R traffics to the nucleus as an IGF-1R/INSR heterotetrameric complex to regulate corneal epithelial homeostatic
Directory of Open Access Journals (Sweden)
Lemos Bernardo
2010-12-01
Full Text Available Abstract Background Hybrid male sterility (HMS is a usual outcome of hybridization between closely related animal species. It arises because interactions between alleles that are functional within one species may be disrupted in hybrids. The identification of genes leading to hybrid sterility is of great interest for understanding the evolutionary process of speciation. In the current work we used marked P-element insertions as dominant markers to efficiently locate one genetic factor causing a severe reduction in fertility in hybrid males of Drosophila simulans and D. mauritiana. Results Our mapping effort identified a region of 9 kb on chromosome 3, containing three complete and one partial coding sequences. Within this region, two annotated genes are suggested as candidates for the HMS factor, based on the comparative molecular characterization and public-source information. Gene Taf1 is partially contained in the region, but yet shows high polymorphism with four fixed non-synonymous substitutions between the two species. Its molecular functions involve sequence-specific DNA binding and transcription factor activity. Gene agt is a small, intronless gene, whose molecular function is annotated as methylated-DNA-protein-cysteine S-methyltransferase activity. High polymorphism and one fixed non-synonymous substitution suggest this is a fast evolving gene. The gene trees of both genes perfectly separate D. simulans and D. mauritiana into monophyletic groups. Analysis of gene expression using microarray revealed trends that were similar to those previously found in comparisons between whole-genome hybrids and parental species. Conclusions The identification following confirmation of the HMS candidate gene will add another case study leading to understanding the evolutionary process of hybrid incompatibility.
Metal-insulator transition at the LaAlO3/SrTiO3 interface revisited: A hybrid functional study
Cossu, Fabrizio
2013-07-17
We investigate the electronic properties of the LaAlO3/SrTiO3 interface using density functional theory. In contrast to previous studies, which relied on (semi-)local functionals and the GGA+U method, we here use a recently developed hybrid functional to determine the electronic structure. This approach offers the distinct advantage of accessing both the metallic and insulating multilayers on a parameter-free equal footing. As compared to calculations based on semilocal GGA functionals, our hybrid functional calculations lead to a considerably increased band gap for the insulating systems. The details of the electronic structure show substantial deviations from those obtained by GGA calculations. This casts severe doubts on all previous results based on semilocal functionals. In particular, corrections using rigid band shifts (“scissors operator”) cannot lead to valid results.
Structural and magnetic properties of TlTF{sub 3} (T=Fe, Co and Ni) by hybrid functional theory
Energy Technology Data Exchange (ETDEWEB)
Zeb, Raham [Center for Computational Materials Science, University of Malakand, Chakdara, Dir (Lower) (Pakistan); Department of Physics, University of Malakand, Chakdara, Dir (Lower) (Pakistan); Ali, Zahid, E-mail: zahidf82@gmail.com [Center for Computational Materials Science, University of Malakand, Chakdara, Dir (Lower) (Pakistan); Department of Physics, University of Malakand, Chakdara, Dir (Lower) (Pakistan); Ahmad, Iftikhar; Khan, Imad [Center for Computational Materials Science, University of Malakand, Chakdara, Dir (Lower) (Pakistan); Department of Physics, University of Malakand, Chakdara, Dir (Lower) (Pakistan)
2015-08-15
DFT studies are performed to investigate the structural, mechanical and magneto-electronic properties of the TlTF{sub 3} (T=Fe, Co and Ni) perovskites for the first time using GGA, GGA+U and hybrid density functional theory (HF). Our calculations show that HF give better results than GGA and GGA+U and more consistent with the experiments. The comparison of the lattice constants calculated by HF with experiments shows a maximum underestimation less than 0.2%. The chemical bonding between different ions in these compounds is explained on the bases of electronic clouds, which reveals that in TlFeF{sub 3}, Fe has more ionic character with F than the rest. The mechanical properties explain the hardness of these compounds and show that TlFeF{sub 3} is more ductile. Spin-dependent electronic band profiles show that TlFeF{sub 3} and TlCoF{sub 3} are metallic, whereas TlNiF{sub 3} is pseudo direct wide bandgap semiconductor. The stable magnetic phase optimizations and the calculated magnetic susceptibility confirm that TlFeF{sub 3} and TlNiF{sub 3} are ferromagnetic whereas TlCoF{sub 3} is anti-ferromagnetic material. - Highlights: • TlTF{sub 3} (T=Fe, Co and Ni) perovskites are investigated theoretically by hybrid density functional theory. • Mechanical properties explain the hardness of these compounds and show that TlFeF{sub 3} is more ductile. • The bandgap calculations show that TlFeF{sub 3} and TlCoF{sub 3} are metallic, whereas TlNiF{sub 3} is a wide bandgap semiconductor. • Magnetic optimizations and magnetic susceptibility confirm that TlFeF{sub 3} and TlNiF{sub 3} are ferromagnetic whereas TlCoF{sub 3} is anti-ferromagnetic material.
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Cristin N. Bock
2017-06-01
Full Text Available Infections by the soil-transmitted threadworm Strongyloides stercoralis affect 30–100 million people worldwide, predominantly in tropic and sub-tropic regions. Here we assessed the T helper cell phenotypes in threadworm-infected patients and experimental murine infections with focus on CD4+ T cells co-expressing markers of Th2 and Th1 differentiation. We show that mice infected with the close relative S. ratti generate strong Th2 responses characterized by the expansion of CD4+ GATA-3+ cells expressing IL-4/-5/-13 in blood, spleen, gut-draining lymph nodes, lung and gut tissue. In addition to conventional Th2 cells, significantly increased frequencies of GATA-3+T-bet+ Th2/1-hybrid cells were detected in all organs and co-expressed Th2- and Th1-cytokines at intermediate levels. Assessing the phenotype of blood-derived CD4+ T cells from South Indian patients infected with S. stercoralis and local uninfected control donors we found that GATA-3 expressing Th2 cells were significantly increased in the patient cohort, coinciding with elevated eosinophil and IgE/IgG4 levels. A fraction of IL-4+CD4+ T cells simultaneously expressed IFN-γ hence displaying a Th2/1 hybrid phenotype. In accordance with murine Th2/1 cells, human Th2/1 cells expressed intermediate levels of Th2 cytokines. Contrasting their murine counterparts, human Th2/1 hybrids were marked by high levels of IFN-γ and rather low GATA-3 expression. Assessing the effector function of murine Th2/1 cells in vitro we found that Th2/1 cells were qualified for driving the classical activation of macrophages. Furthermore, Th2/1 cells shared innate, cytokine-driven effector functions with Th1 cells. Hence, the key findings of our study are that T helper cells with combined characteristics of Th2 and Th1 cells are integral to immune responses of helminth-infected mice, but also occur in helminth-infected humans and we suggest that Th2/1 cells are poised for the instruction of balanced immune
Richardson, T B; Kaspers, J; Porter, C D
2004-05-01
Transcriptional targeting is an important aspect of developing gene therapy vectors in order to restrict transgene expression to selected target cells. One approach, when using retroviral vectors, is to replace viral transcriptional control elements within the long terminal repeat (LTR) with sequences imparting the desired specificity. We have developed such hybrid LTR retroviruses, incorporating sequences from each of the human promoters for flt-1, ICAM-2 and KDR, as part of our antivascular cancer gene therapy strategy targeting tumour endothelial cells. The chosen fragments were used to replace the enhancer or combined enhancer and proximal promoter regions of the viral LTR. All showed activity in primary human breast microvascular endothelial cells, with viruses incorporating ICAM-2 sequences exhibiting the greatest specificity versus nonendothelial cells in vitro and a marked alteration of specificity towards endothelial cells in a subcutaneous xenograft model in vivo. Moreover, our study documents the effect of enhancer and/or proximal promoter deletion on LTR activity and reports that differential dependence in different cell lines can give the false impression of specificity if experiments are not adequately controlled. This finding also has implications for other retroviral vector designs seeking to provide transcriptional specificity and for their safety with respect to prevention of gene activation at sites of proviral integration.
Xing, Yuxiu; Peng, Jun; Xu, Kai; Lin, Weihong; Gao, Shuxi; Ren, Yuanyuan; Gui, Xuefeng; Liang, Shengyuan; Chen, Mingcai
2016-02-01
We prepared core-shell polymer-silsesquioxane hybrid microcapsules from cage-like methacryloxypropyl silsesquioxanes (CMSQs) and styrene (St). The presence of CMSQ can moderately reduce the interfacial tension between St and water and help to emulsify the monomer prior to polymerization. Dynamic light scattering (DLS) and TEM analysis demonstrated that uniform core-shell latex particles were achieved. The polymer latex particles were subsequently transformed into well-defined hollow nanospheres by removing the polystyrene (PS) core with 1:1 ethanol/cyclohexane. High-resolution TEM and nitrogen adsorption-desorption analysis showed that the final nanospheres possessed hollow cavities and had porous shells; the pore size was approximately 2-3 nm. The nanospheres exhibited large surface areas (up to 486 m(2) g(-1) ) and preferential adsorption, and they demonstrated the highest reported methylene blue adsorption capacity (95.1 mg g(-1) ). Moreover, the uniform distribution of the methacryloyl moiety on the hollow nanospheres endowed them with more potential properties. These results could provide a new benchmark for preparing hollow microspheres by a facile one-step template-free method for various applications.
A hybrid method for the parallel computation of Green’s functions
DEFF Research Database (Denmark)
Petersen, Dan Erik; Li, Song; Stokbro, Kurt;
2009-01-01
Quantum transport models for nanodevices using the non-equilibrium Green’s function method require the repeated calculation of the block tridiagonal part of the Green’s and lesser Green’s function matrices. This problem is related to the calculation of the inverse of a sparse matrix. Because...
Shiba, K; Sugiyama, T; Takei, T; Yoshikawa, G
2015-11-11
Silica/titania-based functional nanoparticles were prepared through controlled nucleation of titania and subsequent encapsulation by silica through a multistep microfluidic approach, which was successfully applied to obtaining aminopropyl-functionalized silica/titania nanoparticles for a highly sensitive humidity sensor.
The role of exchange and correlation in time-dependent density-functional theory for photoionization
Stener, M.; Decleva, P.; Görling, A.
2001-05-01
Atomic photoionization cross sections are calculated by time-dependent density-functional (TDDF) methods using different exchange-correlation potentials including the exact one. The exchange-correlation kernel is treated in the adiabatic local density approximation (ALDA). Results for the exact full and the exact exchange-only Kohn-Sham (KS) potential are very similar, the calculated photo cross section agree very well with experimental data. Thus the exact correlation potential seems to have no influence on photoionization and the ALDA for the exchange-correlation kernel seems to be sufficient for most features of the cross sections. The TDDF method employing the exact exchange-only KS potential in combination with the ALDA exchange-correlation kernel therefore is a promising approach to describe photoionization. Deviations from experiment are observed for the widths and shape of the autoionization resonances and have to be attributed to deficiencies of the ALDA exchange-correlation kernel. The calculation of widths and shapes of autoionization resonances therefore may serve as a severe test for new approximate exchange-correlation density-functionals. The asymptotically exact exchange-correlation potential of van Leeuwen and Baerends also leads to quite good photo cross section, which, however, shows deficiencies close to the ionization threshold and in the energetic position of the autoionization resonances. Supplementation of the exact exchange potential with the LDA correlation potential leads to a worsening of the photo cross section because the LDA correlation potential is too attractive.
Guthmuller, Julien; Champagne, Benoît
2007-10-28
The absorption and resonance Raman spectra have been investigated for the first excited state of the julolidinemalononitrile push-pull chromophore in cyclohexane, dichloromethane, and acetonitrile by means of time dependent density functional theory calculations. The effect of nonlocal exchange has been considered by using three different hybrid exchange-correlation functionals containing 20%, 35%, and 50% of exact Hartree-Fock exchange. The interactions with the solvent have been described by the polarizable continuum model. The short-time approximation expression has been used to evaluate the resonance Raman intensities, while the vibronic theory of resonance Raman spectroscopy has been employed to determine both the intensities and the excitation profiles. It is shown that a consistent description of the vibronic structure of the excited state and resonance Raman spectra can be obtained provided that an adequate amount, close to 35%, of exact exchange is included in the exchange-correlation functional. The effect of increasing the polarity of the solvent is well represented by the polarizable continuum model, both for the absorption spectra and resonance Raman intensities. In particular, these simulations can reproduce the observed variations of the 1560 cm(-1) band intensity and attribute them to elongations of a CC double bond upon electronic excitation. Moreover, the short-time approximation has been found sufficient to reproduce most of the results of the more evolved vibronic theory of resonance Raman spectroscopy, which includes summations over vibrational excited states, for both the spectral signatures and their solvent dependencies.
Tanchuk, Vsevolod Yu; Tanin, Volodymyr O; Vovk, Andriy I; Poda, Gennady
2016-04-01
Automated docking is one of the most important tools for structure-based drug design that allows prediction of ligand binding poses and also provides an estimate of how well small molecules fit in the binding site of a protein. A new scoring function based on AutoDock and AutoDock Vina has been introduced. The new hybrid scoring function is a linear combination of the two scoring function components derived from a multiple linear regression fitting procedure. The scoring function was built on a training set of 2412 protein-ligand complexes from pdbbind database (www.pdbbind.org.cn, version 2012). A test set of 313 complexes that appeared in the 2013 version was used for validation purposes. The new hybrid scoring function performed better than the original functions, both on training and test sets of protein-ligand complexes, as measured by the non-parametric Pearson correlation coefficient, R, mean absolute error (MAE), and root-mean-square error (RMSE) between the experimental binding affinities and the docking scores. The function also gave one of the best results among more than 20 scoring functions tested on the core set of the pdbbind database. The new AutoDock hybrid scoring function will be implemented in modified version of AutoDock. © 2015 John Wiley & Sons A/S.
A hybrid Monte Carlo model for the energy response functions of X-ray photon counting detectors
Wu, Dufan; Xu, Xiaofei; Zhang, Li; Wang, Sen
2016-09-01
In photon counting computed tomography (CT), it is vital to know the energy response functions of the detector for noise estimation and system optimization. Empirical methods lack flexibility and Monte Carlo simulations require too much knowledge of the detector. In this paper, we proposed a hybrid Monte Carlo model for the energy response functions of photon counting detectors in X-ray medical applications. GEANT4 was used to model the energy deposition of X-rays in the detector. Then numerical models were used to describe the process of charge sharing, anti-charge sharing and spectral broadening, which were too complicated to be included in the Monte Carlo model. Several free parameters were introduced in the numerical models, and they could be calibrated from experimental measurements such as X-ray fluorescence from metal elements. The method was used to model the energy response function of an XCounter Flite X1 photon counting detector. The parameters of the model were calibrated with fluorescence measurements. The model was further tested against measured spectrums of a VJ X-ray source to validate its feasibility and accuracy.
A hybrid Monte Carlo model for the energy response functions of X-ray photon counting detectors
Energy Technology Data Exchange (ETDEWEB)
Wu, Dufan; Xu, Xiaofei [Key Laboratory of Particle & Radiation Imaging, Tsinghua University, Ministry of Education (China); Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Zhang, Li, E-mail: zli@mail.tsinghua.edu.cn [Key Laboratory of Particle & Radiation Imaging, Tsinghua University, Ministry of Education (China); Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Wang, Sen [Key Laboratory of Particle & Radiation Imaging, Tsinghua University, Ministry of Education (China); Department of Engineering Physics, Tsinghua University, Beijing 100084 (China)
2016-09-11
In photon counting computed tomography (CT), it is vital to know the energy response functions of the detector for noise estimation and system optimization. Empirical methods lack flexibility and Monte Carlo simulations require too much knowledge of the detector. In this paper, we proposed a hybrid Monte Carlo model for the energy response functions of photon counting detectors in X-ray medical applications. GEANT4 was used to model the energy deposition of X-rays in the detector. Then numerical models were used to describe the process of charge sharing, anti-charge sharing and spectral broadening, which were too complicated to be included in the Monte Carlo model. Several free parameters were introduced in the numerical models, and they could be calibrated from experimental measurements such as X-ray fluorescence from metal elements. The method was used to model the energy response function of an XCounter Flite X1 photon counting detector. The parameters of the model were calibrated with fluorescence measurements. The model was further tested against measured spectrums of a VJ X-ray source to validate its feasibility and accuracy.
Sun, Yi-Yang; Zhang, Shengbai
2016-07-01
Bulk black phosphorus has two optical phonon modes labeled as Ag2 and B2u, respectively, that are nearly degenerate in frequency. However, density functional theory calculations using local or semi-local functionals cannot reproduce this degeneracy. Here, we propose a hybrid functional approach aided by van der Waals (vdW) force fields, which can accurately describe the lattice dynamic and electronic properties of both bulk and few-layer black phosphorus (phosphorene). Using this approach we show that in bilayer phosphorene, the two Raman modes derived from the B2u and Ag2 modes could exhibit strong resonance as a result of the accidental degeneracy so that both modes could be observed in Raman experiment. Without the mode degeneracy, however, the Raman intensity of the B2u-derived mode would be too weak to be observed. We further show that the accidental degeneracy is correlated to the applied strain, which enables Raman spectroscopy to be a powerful tool for characterizing built-in strains in 2D materials, e.g., due to the interaction with substrates, which has emerged as an important issue in vdW epitaxy.
Sun, Yi-Yang; Zhang, Shengbai
2016-07-14
Bulk black phosphorus has two optical phonon modes labeled as Ag (2) and B2u, respectively, that are nearly degenerate in frequency. However, density functional theory calculations using local or semi-local functionals cannot reproduce this degeneracy. Here, we propose a hybrid functional approach aided by van der Waals (vdW) force fields, which can accurately describe the lattice dynamic and electronic properties of both bulk and few-layer black phosphorus (phosphorene). Using this approach we show that in bilayer phosphorene, the two Raman modes derived from the B2u and Ag (2) modes could exhibit strong resonance as a result of the accidental degeneracy so that both modes could be observed in Raman experiment. Without the mode degeneracy, however, the Raman intensity of the B2u-derived mode would be too weak to be observed. We further show that the accidental degeneracy is correlated to the applied strain, which enables Raman spectroscopy to be a powerful tool for characterizing built-in strains in 2D materials, e.g., due to the interaction with substrates, which has emerged as an important issue in vdW epitaxy.
Directory of Open Access Journals (Sweden)
Toshiyuki Fujiwara
2017-01-01
Full Text Available Hybrid Assistive Neuromuscular Dynamic Stimulation (HANDS therapy is one of the neurorehabilitation therapeutic approaches that facilitates the use of the paretic upper extremity (UE in daily life by combining closed-loop electromyography- (EMG- controlled neuromuscular electrical stimulation (NMES with a wrist-hand splint. This closed-loop EMG-controlled NMES can change its stimulation intensity in direct proportion to the changes in voluntary generated EMG amplitudes recorded with surface electrodes placed on the target muscle. The stimulation was applied to the paretic finger extensors. Patients wore a wrist-hand splint and carried a portable stimulator in an arm holder for 8 hours during the daytime. The system was active for 8 hours, and patients were instructed to use their paretic hand as much as possible. HANDS therapy was conducted for 3 weeks. The patients were also instructed to practice bimanual activities in their daily lives. Paretic upper extremity motor function improved after 3 weeks of HANDS therapy. Functional improvement of upper extremity motor function and spasticity with HANDS therapy is based on the disinhibition of the affected hemisphere and modulation of reciprocal inhibition. HANDS therapy may offer a promising option for the management of the paretic UE in patients with stroke.
Honaga, Kaoru; Tochikura, Michi; Abe, Kaoru
2017-01-01
Hybrid Assistive Neuromuscular Dynamic Stimulation (HANDS) therapy is one of the neurorehabilitation therapeutic approaches that facilitates the use of the paretic upper extremity (UE) in daily life by combining closed-loop electromyography- (EMG-) controlled neuromuscular electrical stimulation (NMES) with a wrist-hand splint. This closed-loop EMG-controlled NMES can change its stimulation intensity in direct proportion to the changes in voluntary generated EMG amplitudes recorded with surface electrodes placed on the target muscle. The stimulation was applied to the paretic finger extensors. Patients wore a wrist-hand splint and carried a portable stimulator in an arm holder for 8 hours during the daytime. The system was active for 8 hours, and patients were instructed to use their paretic hand as much as possible. HANDS therapy was conducted for 3 weeks. The patients were also instructed to practice bimanual activities in their daily lives. Paretic upper extremity motor function improved after 3 weeks of HANDS therapy. Functional improvement of upper extremity motor function and spasticity with HANDS therapy is based on the disinhibition of the affected hemisphere and modulation of reciprocal inhibition. HANDS therapy may offer a promising option for the management of the paretic UE in patients with stroke. PMID:28191352
Malik, Suheel Abdullah; Qureshi, Ijaz Mansoor; Amir, Muhammad; Malik, Aqdas Naveed; Haq, Ihsanul
2015-01-01
In this paper, a new heuristic scheme for the approximate solution of the generalized Burgers'-Fisher equation is proposed. The scheme is based on the hybridization of Exp-function method with nature inspired algorithm. The given nonlinear partial differential equation (NPDE) through substitution is converted into a nonlinear ordinary differential equation (NODE). The travelling wave solution is approximated by the Exp-function method with unknown parameters. The unknown parameters are estimated by transforming the NODE into an equivalent global error minimization problem by using a fitness function. The popular genetic algorithm (GA) is used to solve the minimization problem, and to achieve the unknown parameters. The proposed scheme is successfully implemented to solve the generalized Burgers'-Fisher equation. The comparison of numerical results with the exact solutions, and the solutions obtained using some traditional methods, including adomian decomposition method (ADM), homotopy perturbation method (HPM), and optimal homotopy asymptotic method (OHAM), show that the suggested scheme is fairly accurate and viable for solving such problems. PMID:25811858
Heavy-impurity resonance, hybridization, and phonon spectral functions in Fe1-xMxSi (M =Ir , Os )
Delaire, O.; Al-Qasir, I. I.; May, A. F.; Li, C. W.; Sales, B. C.; Niedziela, J. L.; Ma, J.; Matsuda, M.; Abernathy, D. L.; Berlijn, T.
2015-03-01
The vibrational behavior of heavy substitutional impurities (M = Ir,Os) in Fe1-xMxSi (x =0 ,0.02 ,0.04 ,0.1 ) was investigated with a combination of inelastic neutron scattering (INS), transport measurements, and first-principles simulations. Our INS measurements on single crystals mapped the four-dimensional dynamical structure factor, S (Q ,E ) , for several compositions and temperatures. Our results show that both Ir and Os impurities lead to the formation of a weakly dispersive resonance vibrational mode, in the energy range of the acoustic phonon dispersions of the FeSi host. We also show that Ir doping, which introduces free carriers, leads to softened interatomic force constants compared to doping with Os, which is isoelectronic to Fe. We analyze the phonon S (Q ,E ) from INS through a Green's-function model incorporating the phonon self-energy based on first-principles density functional theory simulations, and we study the disorder-induced lifetimes on large supercells. Calculations of the quasiparticle spectral functions in the doped system reveal the hybridization between the resonance and the acoustic phonon modes. Our results demonstrate a strong interaction of the host acoustic dispersions with the resonance mode, likely leading to the large observed suppression in lattice thermal conductivity.
Directory of Open Access Journals (Sweden)
Suheel Abdullah Malik
Full Text Available In this paper, a new heuristic scheme for the approximate solution of the generalized Burgers'-Fisher equation is proposed. The scheme is based on the hybridization of Exp-function method with nature inspired algorithm. The given nonlinear partial differential equation (NPDE through substitution is converted into a nonlinear ordinary differential equation (NODE. The travelling wave solution is approximated by the Exp-function method with unknown parameters. The unknown parameters are estimated by transforming the NODE into an equivalent global error minimization problem by using a fitness function. The popular genetic algorithm (GA is used to solve the minimization problem, and to achieve the unknown parameters. The proposed scheme is successfully implemented to solve the generalized Burgers'-Fisher equation. The comparison of numerical results with the exact solutions, and the solutions obtained using some traditional methods, including adomian decomposition method (ADM, homotopy perturbation method (HPM, and optimal homotopy asymptotic method (OHAM, show that the suggested scheme is fairly accurate and viable for solving such problems.
Distributed-parameter problem solved on a hybrid computer by a modified function storage technique
DEFF Research Database (Denmark)
Poulsen, N.J.
1969-01-01
Describes a method which is based on a function storage technique improved by a number of modifications; it fulfils the two main demands: the solution is based directly on the physical equations, and is accurate within 1%......Describes a method which is based on a function storage technique improved by a number of modifications; it fulfils the two main demands: the solution is based directly on the physical equations, and is accurate within 1%...
Energy Technology Data Exchange (ETDEWEB)
Daikopoulos, Chris [Department of Materials Science and Engineering, University of Ioannina, Ioannina 45110 (Greece); Bourlinos, Athanasios B. [Institute of Materials Science, NCSR “Demokritos”, Ag. Paraskevi Attikis, Athens 15310 (Greece); Georgiou, Yiannis [Laboratory of Physical Chemistry, Department of Environmental and Natural Resources Management, University of Patras, Seferi 2, Agrinio 30100 (Greece); Deligiannakis, Yiannis, E-mail: ideligia@cc.uoi.gr [Laboratory of Physical Chemistry, Department of Environmental and Natural Resources Management, University of Patras, Seferi 2, Agrinio 30100 (Greece); Zboril, Radek [Regional Centre of Advanced Technologies and Materials, Faculty of Science, Department of Physical Chemistry and Experimental Physics, Palacky University, Olomouc 77146 (Czech Republic); Karakassides, Michael A. [Department of Materials Science and Engineering, University of Ioannina, Ioannina 45110 (Greece)
2014-04-01
Highlights: • Novel phosphonate-rich organosilica layered hybrid material (PSLM) fabricated through a mild xerogel process. • Surface Complexation Modeling reveals that PSLM bears 2 types of functional groups able to bind heavy metal. • Maximum metal uptake capacities were found 2.72 mmol g{sup −1} for Cu{sup 2+}, 1.67 mmol g{sup −1} for Pb{sup 2+} and 1.00 mmol g{sup −1} for Cd{sup 2+} at pH 7. • EPR spectroscopy reveals local coordination environment for Cu{sup 2+} ions. - Abstract: A phosphonate-rich organosilica layered hybrid material (PSLM) made of 3-(trihydroxysilyl)propyl methylphosphonate, monosodium salt, as the single silica source, has been obtained from its aqueous solution through a xerogel process and mild thermal aging. The method is simple, affording bulk quantities of powdered PSLM in a single-step. The hybrid is stable in water and possesses a high content of phosphonate groups fixed on the solid matrix. In addition, PSLM shows good thermal stability, which exceeds 300 °C in air. The material was characterized using SEM, TEM, XRD, FT-IR and TGA techniques. Potentiometric titrations show that PSLM bears high-surface density of phosphonate groups (3 mmol g{sup −1}). As a result, the material displays high metal uptake capacity for heavy metal ions such as Cu{sup 2+} (2.72 mmol g{sup −1}), Pb{sup 2+} (1.67 mmol g{sup −1}) and Cd{sup 2+} (1.00 mmol g{sup −1}) at neutral pH values e.g. the pH of natural waters. Detailed theoretical modeling using a Surface Complexation Model combined with Electron Paramagnetic Resonance (EPR) spectroscopy shows that the surface distribution of surface bound Cu{sup 2+} ions is rather homogeneous e.g. copper-binding phosphonate sites are arranged in average distances 5–8 Å.
Liu, Yuekun; Liu, Xuegang; Ye, Gang; Song, Yang; Liu, Fei; Huo, Xiaomei; Chen, Jing
2017-05-09
Mesoporous silica/polymer hybrids with well-preserved mesoporosity were prepared by integrating the initiators for continuous activator regeneration (ICAR) atom transfer radical polymerization (ATRP) technique with the bio-inspired polydopamine (PDA) chemistry. By manipulating the auto-oxidative polymerization of dopamine, uniform PDA layers were deposited on the surfaces and pore walls of ordered mesoporous silicas (OMSs), thereby promoting the immobilization of ATRP initiators. Poly(glycidyl methacrylate) (PGMA) brushes were then grown from the OMSs by using the ICAR ATRP technique. The evolution of the mesoporous silica/polymer hybrids during synthesis, in terms of morphology, structure, surface and porous properties, was detailed. And, parameters influencing the controlled growth of polymer chains in the ICAR ATRP system were studied. Taking advantage of the abundant epoxy groups in the PGMA platform, post-functionalization of the mesoporous silica/polymer hybrids by the covalent attachment of macrocyclic ligands for the adsorptive separation of lithium isotopes was realized. Adsorption behavior of the functionalized hybrids toward lithium ions was fully investigated, highlighting the good selectivity, and effects of temperature, solvent and counter ions. The ability for lithium isotope separation was evaluated. A higher separation factor could be obtained in systems with softer counter anions and lower polarity solvents. More importantly, due to the versatility of the ICAR ATRP technique, combined with the non-surface specific PDA chemistry, the methodology established in this work would provide new opportunities for the preparation of advanced organic-inorganic porous hybrids for broadened applications.
Ambade, Swapnil B.; Ambade, Rohan B.; Eom, Seung Hun; Baek, Myung-Jin; Bagde, Sushil S.; Mane, Rajaram S.; Lee, Soo-Hyoung
2016-02-01
In an unprecedented attempt, we present an interesting approach of coupling solution processed ZnO planar nanorods (NRs) by an organic small molecule (SM) with a strong electron withdrawing cyano moiety and the carboxylic group as binding sites by a facile co-functionalization approach. Direct functionalization by SMs (SM-ZnO NRs) leads to higher aggregation owing to the weaker solubility of SMs in solutions of ZnO NRs dispersed in chlorobenzene (CB). A prior addition of organic 2-(2-methoxyethoxy)acetic acid (MEA) over ZnO NRs not only inhibits aggregation of SMs over ZnO NRs, but also provides enough sites for the SM to strongly couple with the ZnO NRs to yield transparent SM-MEA-ZnO NRs hybrids that exhibited excellent capability as electron transporting layers (ETLs) in inverted organic solar cells (iOSCs) of P3HT:PC60BM bulk-heterojunction (BHJ) photoactive layers. A strongly coupled SM-MEA-ZnO NR hybrid reduces the series resistance by enhancing the interfacial area and tunes the energy level alignment at the interface between the (indium-doped tin oxide, ITO) cathode and BHJ photoactive layers. A significant enhancement in power conversion efficiency (PCE) was achieved for iOSCs comprising ETLs of SM-MEA-ZnO NRs (3.64%) advancing from 0.9% for pristine ZnO NRs, while the iOSCs of aggregated SM-ZnO NRs ETL exhibited a much lower PCE of 2.6%, thus demonstrating the potential of the co-functionalization approach. The superiority of the co-functionalized SM-MEA-ZnO NRs ETL is also evident from the highest PCE of 7.38% obtained for the iOSCs comprising BHJ of PTB7-Th:PC60BM compared with extremely poor 0.05% for non-functionalized ZnO NRs.In an unprecedented attempt, we present an interesting approach of coupling solution processed ZnO planar nanorods (NRs) by an organic small molecule (SM) with a strong electron withdrawing cyano moiety and the carboxylic group as binding sites by a facile co-functionalization approach. Direct functionalization by SMs (SM
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Lallier François H
2007-09-01
Full Text Available Abstract Background Since its discovery around deep sea hydrothermal vents of the Galapagos Rift about 30 years ago, the chemoautotrophic symbiosis between the vestimentiferan tubeworm Riftia pachyptila and its symbiotic sulfide-oxidizing γ-proteobacteria has been extensively studied. However, studies on the tubeworm host were essentially targeted, biochemical approaches. We decided to use a global molecular approach to identify new proteins involved in metabolite exchanges and assimilation by the host. We used a Subtractive Suppression Hybridization approach (SSH in an unusual way, by comparing pairs of tissues from a single individual. We chose to identify the sequences preferentially expressed in the branchial plume tissue (the only organ in contact with the sea water and in the trophosome (the organ housing the symbiotic bacteria using the body wall as a reference tissue because it is supposedly not involved in metabolite exchanges in this species. Results We produced four cDNA libraries: i body wall-subtracted branchial plume library (BR-BW, ii and its reverse library, branchial plume-subtracted body wall library (BW-BR, iii body wall-subtracted trophosome library (TR-BW, iv and its reverse library, trophosome-subtracted body wall library (BW-TR. For each library, we sequenced about 200 clones resulting in 45 different sequences on average in each library (58 and 59 cDNAs for BR-BW and TR-BW libraries respectively. Overall, half of the contigs matched records found in the databases with good E-values. After quantitative PCR analysis, it resulted that 16S, Major Vault Protein, carbonic anhydrase (RpCAbr, cathepsin and chitinase precursor transcripts were highly represented in the branchial plume tissue compared to the trophosome and the body wall tissues, whereas carbonic anhydrase (RpCAtr, myohemerythrin, a putative T-Cell receptor and one non identified transcript were highly specific of the trophosome tissue. Conclusion Quantitative PCR
A hybrid radial basis function-pseudospectral method for thermal convection in a 3-D spherical shell
Wright, G. B.
2010-07-01
A novel hybrid spectral method that combines radial basis function (RBF) and Chebyshev pseudospectral methods in a "2 + 1" approach is presented for numerically simulating thermal convection in a 3-D spherical shell. This is the first study to apply RBFs to a full 3-D physical model in spherical geometry. In addition to being spectrally accurate, RBFs are not defined in terms of any surface-based coordinate system such as spherical coordinates. As a result, when used in the lateral directions, as in this study, they completely circumvent the pole issue with the further advantage that nodes can be "scattered" over the surface of a sphere. In the radial direction, Chebyshev polynomials are used, which are also spectrally accurate and provide the necessary clustering near the boundaries to resolve boundary layers. Applications of this new hybrid methodology are given to the problem of convection in the Earth\\'s mantle, which is modeled by a Boussinesq fluid at infinite Prandtl number. To see whether this numerical technique warrants further investigation, the study limits itself to an isoviscous mantle. Benchmark comparisons are presented with other currently used mantle convection codes for Rayleigh number (Ra) 7 × 10^{3} and 10^{5}. Results from a Ra = 10^{6} simulation are also given. The algorithmic simplicity of the code (mostly due to RBFs) allows it to be written in less than 400 lines of MATLAB and run on a single workstation. We find that our method is very competitive with those currently used in the literature. Copyright 2010 by the American Geophysical Union.
Linker, Gerrit-Jan; Loosdrecht , van Paul H.M.; van Duijnen, Piet Th.; Broer, Ria
2015-01-01
The insulating and conducting phases of (EDO-TTF)(2)PF6 were studied by all electron, periodic Hartre-Fock and hybrid density functional calculations. Electronic properties, such as the electronic band structure, the density of states and the Fermi surface are discussed in relation to the metal-insu
2017-04-04
has components that have complex microstructure, such as textile composite, interpenetrating max phase and SMA, and material with vascular...microchannels fabricated by replication of sacrificial components ,” Submitted to Advanced Functional Materials . 7. Benitez R, Proust G, Radovic M...for Multifunctional Nanocomposites", Invited Talk, Seminario de la Unidad de Materiales ( Materials Department Seminar); Centro de Investigacion
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Cheng-Fu Yang
2015-01-01
Full Text Available The new class of multiwalled carbon nanotube (MWCNT/titania nanocomposites was prepared using a sol-gel technique. The addition of titania to MWCNTs has the potential to provide new capability for the development of electrical devices by taking advantage of the favorable electric characteristics of MWCNTs. MWCNTs were first functionalized with carboxyl, acyl chloride, amine, and hydroxyl groups and were then dispersed in a tetraisopropyl titanate (TIPT solution via ultrasonic processing. After gelation, well-dispersed titania in the MWCNT/titania nanocomposites was obtained. Functionalized MWCNTs with varied functional groups were proved by Fourier transform infrared spectroscopy (FT-IR. For the nanocomposites, the degree of the sol-gel process were proved by Raman spectroscopy and wide-angle X-ray diffraction (WAXD. Furthermore, the morphology of the MWCNT/titania nanocomposites was observed using transmission electron microscopy (TEM. In the sol-gel process, the functionalized MWCNTs with carboxyl, acyl chloride, amine, and hydroxyl groups have resulted in the carbon nanotube-graft-titania nanocomposites with a network structure of titania between the carbon nanotubes.
A hybrid microfluidic chip with electrowetting functionality using ultraviolet (UV)-curable polymer
Gu, H.; Duits, Michael H.G.; Mugele, Friedrich Gunther
2010-01-01
Electrowetting (EW) is widely used in digital microfluidics for the manipulation of drops sandwiched between two parallel plates. In contrast, demonstrations of closed microfluidic channels enhanced with EW functionality are scarce. Here, we report a simple, low-cost method to construct such
A hybrid microfluidic chip with electrowetting functionality using ultraviolet (UV)-curable polymer
Gu, Hao; Duits, Michel H.G.; Mugele, Frieder
2010-01-01
Electrowetting (EW) is widely used in digital microfluidics for the manipulation of drops sandwiched between two parallel plates. In contrast, demonstrations of closed microfluidic channels enhanced with EW functionality are scarce. Here, we report a simple, low-cost method to construct such microch
Westerveld, A.J.
2014-01-01
Reach, grasp and release is part of many functional movements. Graying of society leads to more stroke victims and fewer health care professionals. Technology might be a solution to support certain rehabilitation therapies in future health care. Robotic systems have been developed for support of arm
Westerveld, Ard
2014-01-01
Reach, grasp and release is part of many functional movements. Graying of society leads to more stroke victims and fewer health care professionals. Technology might be a solution to support certain rehabilitation therapies in future health care. Robotic systems have been developed for support of arm
Directory of Open Access Journals (Sweden)
Giao Ngoc Nguyen
2017-08-01
Full Text Available Reproductive barriers are commonly observed in both animals and plants, in which they maintain species integrity and contribute to speciation. This report shows that a combination of loss-of-function alleles at two duplicated loci, DUPLICATED GAMETOPHYTIC STERILITY 1 (DGS1 on chromosome 4 and DGS2 on chromosome 7, causes pollen sterility in hybrid progeny derived from an interspecific cross between cultivated rice, Oryza sativa, and an Asian annual wild rice, O. nivara. Male gametes carrying the DGS1 allele from O. nivara (DGS1-nivaras and the DGS2 allele from O. sativa (DGS2-T65s were sterile, but female gametes carrying the same genotype were fertile. We isolated the causal gene, which encodes a protein homologous to DNA-dependent RNA polymerase (RNAP III subunit C4 (RPC4. RPC4 facilitates the transcription of 5S rRNAs and tRNAs. The loss-of-function alleles at DGS1-nivaras and DGS2-T65s were caused by weak or nonexpression of RPC4 and an absence of RPC4, respectively. Phylogenetic analysis demonstrated that gene duplication of RPC4 at DGS1 and DGS2 was a recent event that occurred after divergence of the ancestral population of Oryza from other Poaceae or during diversification of AA-genome species.
Shu, Jian; Qiu, Zhenli; Wei, Qiaohua; Zhuang, Junyang; Tang, Dianping
2015-10-01
5,10,15,20-Tetraphenyl-21H,23H-porphine cobalt flat stacking on the reduced graphene oxide with platinum nanoparticles (PtNPs/CoTPP/rGO) were first synthesized and functionalized with monoclonal rabbit anti-aflatoxin B1 antibody (anti-AFB1) for highly efficient electrochemical immunoassay of aflatoxin B1 (AFB1) in this work. Transmission electron microscopy (TEM), atomic force microscope (AFM) and spectral techniques were employed to characterize the PtNPs/CoTPP/rGO hybrids. Using anti-AFB1-conjugated PtNPs/CoTPP/rGO as the signal-transduction tag, a novel non-enzymatic electrochemical immunosensing system was designed for detection of target AFB1 on the AFB1-bovine serum albumin-functionalized sensing interface. Experimental results revealed that the designed immunoassay could exhibit good electrochemical responses for target analyte and allowed the detection of AFB1 at a concentration as low as 5.0 pg mL-1 (5.0 ppt). Intra- and inter-assay coefficients of variation were below 10%. Importantly, the methodology was further validated for analyzing naturally contaminated or spiked blank peanut samples with consistent results obtained by AFB1 ELISA kit, thus providing a promising approach for quantitative monitoring of organic pollutants.
Shi, Haifeng; Lan, Benyue; Zhang, Chengliang; Ye, Enjia; Nie, Yanguang; Bian, Baoan
2016-10-01
The influences of a series of anion doping on the electronic structures of sodium niobate (NaNbO3) have been systematically investigated by density functional theory (DFT) calculations with the hybrid B3LYP functional. As for B(C,P)-doped NaNbO3, the isolated B 2p (C 2p, P 3p) states were formed above the valence band maximum (VBM) of NaNbO3, which were too weak to mix with O 2p states and thus produced band gap narrowing. While the band gap of NaNbO3 was slightly narrowed after F doping. As for S-doped NaNbO3, the S 3p states mixed with O 2p states well and thus reduced the band gap energy. According to the calculation results, we tentatively put forward that S doping would be appropriate for single anion doping NaNbO3, while the B(C,P) elements would be suitable candidates for co-doping NaNbO3.
Energy Technology Data Exchange (ETDEWEB)
LU,YUNFENG; FAN,HONGYOU; DOKE,NILESH; LOY,DOUGLAS A.; ASSINK,ROGER A.; LAVAN,DAVID A.; BRINKER,C. JEFFREY
2000-06-12
Since the discovery of surfactant-templated silica mesophases, the development of organic modification schemes to impart functionality to the pore surfaces has received much attention. Most recently, using the general class of compounds referred to as bridged silsesquioxanes (RO){sub 3}Si-R{prime}-Si(OR){sub 3} (Scheme 1), three research groups have reported the formation of a new class of poly(bridgedsilsesquioxane) mesophases BSQMs with integral organic functionality. In contrast to previous hybrid mesophases where organic ligands or molecules are situated on pore surfaces, this class of materials necessarily incorporates the organic constituents into the framework as molecularly dispersed bridging ligands. Although it is anticipated that this new mesostructural organization should result in synergistic properties derived from the molecular scale mixing of the inorganic and organic components, few properties of BSQMs have been measured. In addition samples prepared to date have been in the form of granular precipitates, precluding their use in applications like membranes, fluidics, and low k dielectric films needed for all foreseeable future generations of microelectronics.
Feiner, Ron; Engel, Leeya; Fleischer, Sharon; Malki, Maayan; Gal, Idan; Shapira, Assaf; Shacham-Diamand, Yosi; Dvir, Tal
2016-01-01
In cardiac tissue engineering approaches to treat myocardial infarction, cardiac cells are seeded within three-dimensional porous scaffolds to create functional cardiac patches. However, current cardiac patches do not allow for online monitoring and reporting of engineered-tissue performance, and do not interfere to deliver signals for patch activation or to enable its integration with the host. Here, we report an engineered cardiac patch that integrates cardiac cells with flexible, free-standing electronics and a 3D nanocomposite scaffold. The patch exhibited robust electronic properties, enabling the recording of cellular electrical activities and the on-demand provision of electrical stimulation for synchronizing cell contraction. We also show that electroactive polymers containing biological factors can be deposited on designated electrodes to release drugs in the patch microenvironment on-demand. We expect that the integration of complex electronics within cardiac patches will eventually provide therapeutic control and regulation of cardiac function. PMID:26974408
Aggregate Malanobis Distance Function Approach to Evolve a HYBRID AWALE Player
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Keneilwe Zuva
2012-08-01
Full Text Available The game of Awale is a member of the Mancala family.The problem of developing a good agent for playing Mancala games by a computer agent is an open issue. This study presents an agent that is based on the combination of Minimax search and Aggregate Malanobis Distance Function (AMDF, to evolve an agent that can play Awale at a competitive level. The result of the combination is appealing.
Energy Technology Data Exchange (ETDEWEB)
Aguayo, Aaron, E-mail: aguayo@uady.mx [Facultad de Matematicas, Universidad Autonoma de Yucatan, Apartado Postal 172, Cordemex, 97110 Merida, Yucatan (Mexico); Murrieta, Gabriel, E-mail: murrieta@uady.mx [Facultad de Matematicas, Universidad Autonoma de Yucatan, Apartado Postal 172, Cordemex, 97110 Merida, Yucatan (Mexico)
2011-12-15
The half-metallic state in the Heusler alloys Co{sub 2}MSn (M = Ti, Zr, Hf) was studied by means of first principles calculation, using both, the Local Spin Density Approximation (LSDA) and the Generalized Gradient Approximation (GGA) to the exchange-correlation energy. While the GGA calculation shows that the three alloys are half-metallic ferromagnets, the LSDA results show that they are ferromagnetic but not half-metallic systems. The difference between the exchange-correlation functionals is analyzed through the electronic structure of the alloys. The origin of the gap in the minority spin channel for GGA calculations is discussed. - Highlights: > In Co{sub 2}MSn (M = Ti, Zr, and Hf) LSDA and GGA act differently on the orbitals. > LSDA and GGA results about their half-metallic estate differ. GGA are half-metallic. > LSDA miscalculated the occupied and unoccupied Co d orbitals. > The calculated magnetic moment also shows differences between the two functionals. > The Co-Co hybridization is central to explain the half-metallic state in these alloys.
Rawolle, Monika; Niedermeier, Martin A; Kaune, Gunar; Perlich, Jan; Lellig, Philipp; Memesa, Mine; Cheng, Ya-Jun; Gutmann, Jochen S; Müller-Buschbaum, Peter
2012-08-07
Nanostructured titania films are of growing interest due to their application in future photovoltaic technologies. Therefore, a lot of effort has been put into the controlled fabrication and tailoring of titania nanostructures. The controlled sol-gel synthesis of titania, in particular in combination with block copolymer templates, is very promising because of its high control on the nanostructure, easy application and cheap processing possibilities. This tutorial review gives a short overview of the structural control of titania films gained by using templated sol-gel chemistry and shows how this approach is extended by the addition of further functionality to the films. Different expansions of the sol-gel templating are possible by the fabrication of gradient samples, by the addition of a homopolymer, by the combination with micro-fluidics and also by the application of novel precursors for low-temperature processing. Moreover, hierarchically structured titania films can be fabricated via the subsequent application of several sol-gel steps or via the inclusion of colloidal templates in a one-step process. Integrated function in the block copolymer used in the sol-gel synthesis allows for the fabrication of an integrated blocking layer or an integrated hole-conductor. Both approaches grant a one-step fabrication of two components of a working solar cell, which make them very promising towards a cheap solar cell production route. Looking to the complete solar cell, the top contact is also of great importance as it influences the function of the whole solar cell. Thus, the mechanisms acting in the top contact formation are also reviewed. For all these aspects, characterization techniques that allow for a structural investigation of nanostructures inside the active layers are important. Therefore, the characterization techniques that are used in real space as well as in reciprocal space are explained shortly as well.
Ramesh, Sivalingam; Kim, Gwang-Hoon; Kim, Heung-Soo; Kim, Jaehwan; Kim, Joo-Hyung
2013-04-01
The general class of organic-inorganic hybrid nanocomposites materials is a fast growing area of research. The significant effort is focused on the ability to control the nanoscale structures via organic functional synthetic approaches with inorganic metal oxides. The properties of nanocomposites material depends on the properties of their individual components but also their morphological and interfacial characteristics. This rapidly expanding field is generating many exciting new materials with novel properties. Mainly, cellulose is considered as the richest renewable materials are presently among the most promising candidates for use in photonics due to their versatility, flexibility, light weight, low cost and ease of modification. Cellulose-metal oxide nanomaterials were developed the technologies to manipulate selfassembly and multifunctionallity, of new technologies to the point where industry can produce advanced and costcompetitive cellulose metal oxide hybrid materials. Therefore, the present study is focused on cellulose-functionalized - 4, 4'-(propane-2, 2'-diyl) diphenol-SiO2/TiO2 hybrid nano-composites materials by in-situ sol-gel process. The chemical and morphological properties of cellulose-functionalized SiO2/TiO2 materials via covalent crosslinking hybrids were characterized by FTIR, XRD, TGA, DSC, SEM, TEM and optical properties.
Ko, Hsin-Yu; Santra, Biswajit; Distasio, Robert A., Jr.; Wu, Xifan; Car, Roberto
Hybrid functionals are known to alleviate the self-interaction error in density functional theory (DFT) and provide a more accurate description of the electronic structure of molecules and materials. However, hybrid DFT in the condensed-phase has a prohibitively high associated computational cost which limits their applicability to large systems of interest. In this work, we present a general-purpose order(N) implementation of hybrid DFT in the condensed-phase using Maximally localized Wannier function; this implementation is optimized for massively parallel computing architectures. This algorithm is used to perform large-scale ab initio molecular dynamics simulations of liquid water, ice, and aqueous ionic solutions. We have performed simulations in the isothermal-isobaric ensemble to quantify the effects of exact exchange on the equilibrium density properties of water at different thermodynamic conditions. We find that the anomalous density difference between ice I h and liquid water at ambient conditions as well as the enthalpy differences between ice I h, II, and III phases at the experimental triple point (238 K and 20 Kbar) are significantly improved using hybrid DFT over previous estimates using the lower rungs of DFT This work has been supported by the Department of Energy under Grants No. DE-FG02-05ER46201 and DE-SC0008626.
Nathan, R H; Ohry, A
1990-05-01
A new, computerized neuromuscular stimulation system was applied to the upper limbs of two patients with complete quadriplegia below the C4 level. The stimulation-generated movements were integrated and augmented by residual, voluntary shoulder girdle movements and mechanical splinting. Up to 12 muscles were stimulated individually with high-resolution surface electrodes; coordination and control of the stimulation was effected by microcomputer. Simple vocal commands to the computer triggered preprogrammed hand prehensions, arm motion, and other functions, giving the patient complete control over the system. In pilot clinical trials of six weeks, writing, eating, and drinking, including picking up and replacing the pen or cup, were achieved.
Cui, Wei; Lansac, Yves; Lee, Hochun; Hong, Seung-Tae; Jang, Yun Hee
2016-09-14
Complex formation between lithium (Li(+)) ions and electrolyte molecules would affect the ionic conductivity through the electrolyte in lithium-ion batteries (LIBs). We hence revisit the solvation number of Li(+) in the most commonly used ethylene carbonate (EC) electrolyte. The solvation number n of Li(+)(EC)n in the first solvation shell of Li(+) is estimated on the basis of the free energy calculated by the density functional theory combined with a hybrid solvation model where the explicit solvation shell of Li(+) is immersed in a free volume of an implicit bulk solvent. This new hybrid solvation (implicit and explicit) model predicts the most probable solvation number (n = 4) and solvation free energy (-91.3 kcal mol(-1)) of Li(+) in a good agreement with those predicted by calculations employing simpler solvation models (either implicit or explicit). The desolvation (n = 2) of Li(0)(EC)n upon reduction near anodes is also well described with this new hybrid model.
Energy Technology Data Exchange (ETDEWEB)
Ünal, Hatice; Mete, Ersen, E-mail: emete@balikesir.edu.tr [Deparment of Physics, Balikesir University, Balikesir 10145 (Turkey); Gunceler, Deniz [Deparment of Physics, Cornell University, Ithaca, New York 14853 (United States); Gülseren, Oğuz [Department of Physics, Bilkent University, Ankara 06800 (Turkey); Ellialtioğlu, Şinasi [Basic Sciences, TED University, Ankara 06420 (Turkey)
2015-11-21
The adsorption of two different organic molecules cyanidin glucoside (C{sub 21}O{sub 11}H{sub 20}) and TA-St-CA on anatase (101) and (001) nanowires has been investigated using the standard and the range separated hybrid density functional theory calculations. The electronic structures and optical spectra of resulting dye–nanowire combined systems show distinct features for these types of photochromophores. The lowest unoccupied molecular orbital of the natural dye cyanidin glucoside is located below the conduction band of the semiconductor while, in the case of TA-St-CA, it resonates with the states inside the conduction band. The wide-bandgap anatase nanowires can be functionalized for solar cells through electron-hole generation and subsequent charge injection by these dye sensitizers. The intermolecular charge transfer character of Donor-π-Acceptor type dye TA-St-CA is substantially modified by its adsorption on TiO{sub 2} surfaces. Cyanidin glucoside exhibits relatively stronger anchoring on the nanowires through its hydroxyl groups. The atomic structures of dye–nanowire systems re-optimized with the inclusion of nonlinear solvation effects showed that the binding strengths of both dyes remain moderate even in ionic solutions.
Huang, Guang; Sun, Zhen; Qin, Hongqiang; Zhao, Liang; Xiong, Zhichao; Peng, Xiaojun; Ou, Junjie; Zou, Hanfa
2014-05-07
Hydrazide chemistry is a powerful technique in glycopeptides enrichment. However, the low density of the monolayer hydrazine groups on the conventional hydrazine-functionalized magnetic nanoparticles limits the efficiency of glycopeptides enrichment. Herein, a novel magnetic nanoparticle grafted with poly(glycidyl methacrylate) (GMA) brushes was fabricated via reversible addition-fragmentation chain transfer (RAFT) polymerization, and a large amount of hydrazine groups were further introduced to the GMA brushes by ring-opening the epoxy groups with hydrazine hydrate. The resulting magnetic nanoparticles (denoted as Fe3O4@SiO2@GMA-NHNH2) demonstrated the high specificity of capturing glycopeptides from a tryptic digest of the sample comprising a standard non-glycosylated protein bovine serum albumin (BSA) and four standard glycoproteins with a weight ratio of 50 : 1, and the detection limit was as low as 130 fmol. In the analysis of a real complex biological sample, the tryptic digest of hepatocellular carcinoma, 179 glycosites were identified by the Fe3O4@SiO2@GMA-NHNH2 nanoparticles, surpassing that of 68 glycosites by Fe3O4@SiO2-single-NHNH2 (with monolayer hydrazine groups on the surface). It can be expected that the magnetic nanoparticles modified with hydrazine functionalized polymer brushes via RAFT technique will improve the specificity and the binding capacity of glycopeptides from complex samples, and show great potential in the analysis of protein glycosylation in biological samples.
Finding zeros of nonlinear functions using the hybrid parallel cell mapping method
Xiong, Fu-Rui; Schütze, Oliver; Ding, Qian; Sun, Jian-Qiao
2016-05-01
Analysis of nonlinear dynamical systems including finding equilibrium states and stability boundaries often leads to a problem of finding zeros of vector functions. However, finding all the zeros of a set of vector functions in the domain of interest is quite a challenging task. This paper proposes a zero finding algorithm that combines the cell mapping methods and the subdivision techniques. Both the simple cell mapping (SCM) and generalized cell mapping (GCM) methods are used to identify a covering set of zeros. The subdivision technique is applied to enhance the solution resolution. The parallel implementation of the proposed method is discussed extensively. Several examples are presented to demonstrate the application and effectiveness of the proposed method. We then extend the study of finding zeros to the problem of finding stability boundaries of potential fields. Examples of two and three dimensional potential fields are studied. In addition to the effectiveness in finding the stability boundaries, the proposed method can handle several millions of cells in just a few seconds with the help of parallel computing in graphics processing units (GPUs).
Sultana, Irin; Rahman, Md Mokhlesur; Ramireddy, Thrinathreddy; Sharma, Neeraj; Poddar, Debasis; Khalid, Abbas; Zhang, Hongzhou; Chen, Ying; Glushenkov, Alexey M
2015-09-23
A range of high-capacity Li-ion anode materials (conversion reactions with lithium) suffer from poor cycling stability and limited high-rate performance. These issues can be addressed through hybridization of multiple nanostructured components in an electrode. Using a Co3O4-Fe2O3/C system as an example, we demonstrate that the cycling stability and rate performance are improved in a hybrid electrode. The hybrid Co3O4-Fe2O3/C electrode exhibits long-term cycling stability (300 cycles) at a moderate current rate with a retained capacity of approximately 700 mAh g(-1). The reversible capacity of the Co3O4-Fe2O3/C electrode is still about 400 mAh g(-1) (above the theoretical capacity of graphite) at a high current rate of ca. 3 A g(-1), whereas Co3O4-Fe2O3, Fe2O3/C, and Co3O4/C electrodes (used as controls) are unable to operate as effectively under identical testing conditions. To understand the structure-function relationship in the hybrid electrode and the reasons for the enhanced cycling stability, we employed a combination of ex situ and in situ techniques. Our results indicate that the improvements in the hybrid electrode originate from the combination of sequential electrochemical activity of the transition metal oxides with an enhanced electronic conductivity provided by percolating carbon chains.
Directory of Open Access Journals (Sweden)
Anna Litvinenko
2013-05-01
Full Text Available The communication patterns of our society have undergone crucial changes due to the development of the digital public sphere and the formation of ‘hybrid media systems’ (Chadwick 2011. This transformation challenges professional journalism in its role as the fourth estate. It is obviously essential to re-think the role and functions of mass media in the modern ‘network society’ (Castells, 2010. Some experts even talk about the end of the “century of journalism” (Weischenberg, 2010, and others argue that it is just the end of the 20th century’s news-journalism and the beginning of the new kind of professional journalism that will still be able to fulfill its core functions of building the public sphere, in accordance with the conditions of the transformed society (Pöttker, 2012. For conventional mass media that means a major switch from ‘news’- journalism to ‘orientation’ journalism (Bruns, 2005. This transformation has been intensified in Russia by the protest movement that fueled a discussion among journalists about new standards of journalism: should they just be observers or are they allowed and even supposed be activists of social movements? This paper examines what this paradigmatic shift means to the profession and to the self-identification of journalists as it is being viewed in Russia and in Germany. The author presents arguments of journalism scholars and journalists from both countries and argues that this development brings along a number of serious challenges for the society, connected with an enormous rise of opinion writing that leads journalists back to the era of pre-professional and precommercial journalism. In order to preserve journalism as a profession with socially important functions, a revision of the concept and of the standards of journalism is needed, both in Germany and in Russia.
Peter, Katherine T; Johns, Adam J; Myung, Nosang V; Cwiertny, David M
2017-06-15
Via a single-pot electrospinning synthesis, we developed a functionalized polymer-metal oxide nanofiber filter for point of use (POU) water treatment of metal oxyanions (e.g., arsenate and chromate). Polyacrylonitrile (PAN) functionalization was accomplished by inclusion of surface-active, quaternary ammonium salts (QAS) [cetyltrimethylammonium bromide (CTAB) or tetrabutylammonium bromide (TBAB)] that provide strong base ion exchange sites. Embedded iron oxide [ferrihydrite (Fh)] nanoparticles were used for their established role as metal sorbents. We examined the influence of QAS and Fh loading on composite properties, including nanofiber morphology, surface area, surface chemical composition, and the accessibility of embedded nanoparticles to solution. Composite performance was then evaluated using kinetic, isotherm, and pH-edge sorption experiments with arsenate and chromate, and benchmarked to unmodified PAN nanofibers and freely dispersed Fh nanoparticles. We also assessed the long-term stability of QAS in the composite matrix. For composites containing QAS or Fh nanoparticles, increasing QAS/Fh nanoparticle loading generally yielded increasing metal oxyanion uptake. The optimized composite (PAN 7 wt%, Fh 3 wt%, TBAB 1 wt%) exhibited two distinct sites for simultaneous, non-competitive metal binding (i.e., iron oxide sites for arsenate removal via sorption and well-retained QAS sites for chromate removal via ion exchange). Moreover, surface-segregating QAS enriched Fh abundance at the nanofiber surface, allowing immobilized nanoparticles to exhibit reactivity comparable to that of unsupported (i.e., suspended or freely dispersed) nanoparticles. To simulate POU application, the optimized composite was tested in a dead-end, flow-through filtration system for arsenate and chromate removal at environmentally relevant concentrations (e.g., μg/L) in both idealized and simulated tap water matrices. Performance trends indicate that dual mechanisms for uptake are
Rigoni, F.; Pintossi, C.; Drera, G.; Pagliara, S.; Lanti, G.; Castrucci, P.; de Crescenzi, M.; Sangaletti, L.
2017-03-01
A combination of the functionalities of carbon nanotube (CNT)-Si hybrid heterojunctions is presented as a novel method to steer the efficiency of the photovoltaic (PV) cell based on these junctions, and to increase the selectivity and sensitivity of the chemiresistor gas sensor operated with the p-doped CNT layer. The electrical characteristics of the junctions have been tracked by exposing the devices to oxidizing (NO2) and reducing (NH3) molecules. It is shown that when used as PV cells, the cell efficiency can be reversibly steered by gas adsorption, providing a tool to selectively dope the p-type layer through molecular adsorption. Tracking of the current-voltage curve upon gas exposure also allowed to use these cells as gas sensors with an enhanced sensitivity as compared to that provided by a readout of the electrical signal from the CNT layer alone. In turn, the chemiresistive response was improved, both in terms of selectivity and sensitivity, by operating the system under illumination, as the photo-induced charges at the junction increase the p-doping of CNTs making them more sensitive to NH3 and less to NO2.
Ma, Li; Ray, Asok K.
2010-03-01
As a continuation of our studies of pure actinide metals using hybrid density functional theory,footnotetextR. Atta-Fynn and A. K. Ray, Europhysics Letters, 85, 27008-p1- p6 (2009); Chemical Physics Letters, 482, 223-227 (2009). we present here a systematic study of the electronic and geometric structure properties of mixed actinide dioxides, U0.5Pu0.5O2, U0.5Am0.5O2, Pu0.5Am0.5 O2 and U0.8Pu0.2O2. The fraction of exact Hartree-Fock exchange used was 40%. To investigate the effect of spin-orbit coupling on the ground state electronic and geometric structure properties, computations have been carried out at two theoretical levels, one at the scalar-relativistic level with no spin-orbit coupling and one at the fully relativistic level with spin-orbit coupling. Thermodynamic properties have been calculated by a coupling of first-principles calculation and lattice dynamics.
Institute of Scientific and Technical Information of China (English)
Xu Sun; You-song Gu; Xue-qiang Wang; Yue Zhang
2012-01-01
The electronic properties and stability of Li-doped ZnO with various defects have been studied by calculating the electronic structures and defect formation energies via first-principles calculations using hybrid Hartree-Fock and density functional methods.The results from formation energy calculations show that Li pair complexes have the lowest formation energy in most circumstances and they consume most of the Li content in Li doped ZnO,which make the p-type conductance hard to obtain.The formation of Li pair complexes is the main obstacle to realize p-type conductance in Li doped ZnO.However,the formation energy of Lizn decreases as environment changes from Zn-rich to O-rich and becomes more stable than that of Li-pair complexes at highly O-rich environment.Therefore,p-type conductance can be obtained by Li doped ZnO grown or post annealed in oxygen rich atmosphere.
Enkin, Natalie; Sharon, Etery; Golub, Eyal; Willner, Itamar
2014-08-13
Luminescent Ag nanoclusters (NCs) stabilized by nucleic acids are implemented as optical labels for the detection of the explosives picric acid, trinitrotoluene (TNT), and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). The sensing modules consist of two parts, a nucleic acid with the nucleic acid-stabilized Ag NCs and a nucleic acid functionalized with electron-donating units, including L-DOPA, L-tyrosine and 6-hydroxy-L-DOPA, self-assembled on a nucleic acid scaffold. The formation of donor-acceptor complexes between the nitro-substituted explosives, exhibiting electron-acceptor properties, and the electron-donating sites, associated with the sensing modules, concentrates the explosives in close proximity to the Ag NCs. This leads to the electron-transfer quenching of the luminescence of the Ag NCs by the explosive molecule. The quenching of the luminescence of the Ag NCs provides a readout signal for the sensing process. The sensitivities of the analytical platforms are controlled by the electron-donating properties of the donor substituents, and 6-hydroxy-L-DOPA was found to be the most sensitive donor. Picric acid, TNT, and RDX are analyzed with detection limits corresponding to 5.2 × 10(-12) M, 1.0 × 10(-12) M, and 3.0 × 10(-12) M, respectively, using the 6-hydroxy-L-DOPA-modified Ag NCs sensing module.
Removal of phosphate by Fe-coordinated amino-functionalized 3D mesoporous silicates hybrid materials
Institute of Scientific and Technical Information of China (English)
Jianda Zhang; Zhemin Shen; Zhijian Mei; Shanping Li; Wenhua Wang
2011-01-01
Phosphate removal from aqueous waste streams is an important approach to control the eutrophication downstream bodies of water.A Fe(Ⅲ) coordinated amino-functionalized silicate adsorbent for phosphate adsorption was synthesized by a post-grafting and metal cation incorporation process. The surface structure of the adsorbent was characterized by X-ray diffraction, N2 adsoropion/desoprotion technique, and Fourier transform infrared spectroscopy. The experimental results showed that the adsorption equilibrium data were well fitted to the Langmuir equation. The maximum adsorption capacity of the modified silicate material was 51.8 mg/g. The kinetic data from the adsorption of phosphate were fitted to pseudo second-order model. The phosphate adsorption was highly pH dependent and the relatively high removal of phosphate fell within the pH range 3.0-6.0. The coexistence of other anions in soiutions has an adverse effect on phosphate adsorption; a decrease in adsorption capacity followed the order of exogenous anions: F- ＞ SO42- ＞ NO3- ＞ Cl-. In addition, the adsorbed phosphate could be desorbed by NaOH solutions. This silicate adsorbent with a large adsorption capacity and relatively high selectivity could be utilized for the removal of phosphate from aqueous waste streams or in aquatic environment.
Photofunctional hybrids of lanthanide functionalized bio-MOF-1 for fluorescence tuning and sensing.
Shen, Xiang; Yan, Bing
2015-08-01
A series of luminescent Ln(3+)@bio-MOF-1 (Ln=Eu, Tb, bio-MOF-1=Zn8(ad)4(BPDC)6O⋅2Me2NH2 (ad=adeninate, BPDC=biphenyldicarboxylate)) are synthesized via postsynthetic cation exchange by encapsulating lanthanide ions into an anionic metal-organic framework (MOF), and their photophysical properties are studied. After loading 2-thenoyltrifluroacetone (TTA) as sensitized ligand by a gas diffusion ("ship-in-bottle") method, it is found that the luminescent intensity of Eu(3+) is enhanced. Especially, when loading two different lanthanide cations into bio-MOF-1, the luminescent color can be tuned to close white (light pink) light output. Additionally, bio-MOF-1 and Eu(3+)@bio-MOF-1 are selected as representative samples for sensing metal ions. When bio-MOF-1 is immersed in the aqueous solutions of different metal ions, it shows highly sensitive sensing for Fe(3+) as well as Eu(3+)@bio-MOF-1 immersed in the DMF solutions of different metal ion. The results are benefit for the further application of functionalized bio-MOFs in practical fields. Copyright © 2015 Elsevier Inc. All rights reserved.
A hybrid microfluidic chip with electrowetting functionality using ultraviolet (UV)-curable polymer.
Gu, Hao; Duits, Michel H G; Mugele, Frieder
2010-06-21
Electrowetting (EW) is widely used in digital microfluidics for the manipulation of drops sandwiched between two parallel plates. In contrast, demonstrations of closed microfluidic channels enhanced with EW functionality are scarce. Here, we report a simple, low-cost method to construct such microchannels enclosed between two glass plates, each of which comprises electrodes and insulating layers. Our method uses soft imprint lithography with thiolene precursors to design the channel geometry. UV exposure is used to seal the chips permanently and a silanization treatment renders all inner channel surfaces hydrophobic. Compared to earlier polydimethylsiloxane-based designs, this method allows us to make microchannels with smaller dimensions (down to 10 microns), lower aspect ratios (down to height/length=1/10), and symmetric electrodes both on the top and the bottom of the channel. We demonstrate the new capabilities with two examples: (i) EW-enhanced drop generation in a flow focusing geometry allows precise and continuous control on drop diameter in the range approximately 1-15 microns while maintaining monodispersity; (ii) EW allows tuning of the excess water pressure needed to displace oil in a microchannel, leading to spontaneous imbibition at EW number eta>0.89.
Curvature and Frontier Orbital Energies in Density Functional Theory.
Stein, Tamar; Autschbach, Jochen; Govind, Niranjan; Kronik, Leeor; Baer, Roi
2012-12-20
Perdew et al. discovered two different properties of exact Kohn-Sham density functional theory (DFT): (i) The exact total energy versus particle number is a series of linear segments between integer electron points. (ii) Across an integer number of electrons, the exchange-correlation potential "jumps" by a constant, known as the derivative discontinuity (DD). Here we show analytically that in both the original and the generalized Kohn-Sham formulation of DFT the two properties are two sides of the same coin. The absence of a DD dictates deviation from piecewise linearity, but the latter, appearing as curvature, can be used to correct for the former, thereby restoring the physical meaning of orbital energies. A simple correction scheme for any semilocal and hybrid functional, even Hartree-Fock theory, is shown to be effective on a set of small molecules, suggesting a practical correction for the infamous DFT gap problem. We show that optimally tuned range-separated hybrid functionals can inherently minimize both DD and curvature, thus requiring no correction, and that this can be used as a sound theoretical basis for novel tuning strategies.
Li, H.; Gillen, R.; Robertson, J.
2016-06-01
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.
A Mathematical Approach to Hybridization
Matthews, P. S. C.; Thompson, J. J.
1975-01-01
Presents an approach to hybridization which exploits the similarities between the algebra of wave functions and vectors. This method will account satisfactorily for the number of orbitals formed when applied to hybrids involving the s and p orbitals. (GS)
Cao, Dapeng; Jiang, Tao; Wu, Jianzhong
2006-04-28
A hybrid method is proposed to investigate the microstructure of various polymeric fluids confined between two parallel surfaces. The hybrid method combines a single-chain Monte Carlo (MC) simulation for the ideal-gas part of the Helmholtz energy and a density functional theory (DFT) for the excess part that arises from nonbonded intersegment interactions. The latter consists of a modified fundamental measure theory for excluded-volume effect, the first-order thermodynamics perturbation theory for chain connectivity, and a mean-field approximation for the van der Waals attraction. In comparison with a conventional DFT, the hybrid method avoids calculation of the time-consuming recursive functions and is directly applicable to polymers with arbitrary molecular architecture. Its numerical performance has been validated by extensive comparisons with MC data for the density distributions of totally flexible, semiflexible, or rigid polymers and those with starlike architecture. Special attention is also given to the formation of a nematic monolayer by rigid molecules laying perpendicular to a planar surface. The hybrid method predicts the surface pressure versus surface coverage in good agreement with experiment.
Hybrid density functional calculations of the defect properties of ZnO:Rh and ZnO:Ir
Energy Technology Data Exchange (ETDEWEB)
Muñoz Ramo, David, E-mail: dm586@cam.ac.uk; Bristowe, Paul D., E-mail: pdb1000@cam.ac.uk
2014-03-31
We report density functional calculations of the atomic and electronic structure of the spinel phases ZnRh{sub 2}O{sub 4} and ZnIr{sub 2}O{sub 4} as well as crystalline ZnO lightly doped (1 at.%) with Rh and Ir ions using the B3LYP hybrid functional. Calculations for the spinels show band gaps (∼ 3 eV) and lattice parameters (∼ 2% difference) in reasonable agreement with experimental data. Incorporation of the transition metals into ZnO induces local distortions in the lattice and the appearance of metal d levels in the low gap region and near the conduction band minimum, with a d–d splitting of about 2 eV, which reduces the effective transparency of the material. Addition of a hole to the simulation cell of both spinels and doped ZnO leads to charge localization in the neighbourhood of Rh/Ir accompanied by local lattice deformations to form a small polaron which may lead to low hole mobility. We calculate polaron diffusion barriers in the spinels and obtain values around 0.02–0.03 eV. These very low barrier energies suggest that at high Rh/Ir concentrations polaron hopping is not going to be detected at room temperature. - Highlights: • Rh/Ir incorporation into ZnO at low doping induces local distortions in the lattice. • Localized levels appear in the gap of ZnO:Rh/ZnO:Ir near band edges. • Hole trapping is found in ZnO:Rh/ZnO:Ir and in the ZnRh{sub 2}O{sub 4}/ZnIr{sub 2}O{sub 4} spinels. • Hole diffusion barriers in the spinels are very small.
Körzdörfer, Thomas
2014-11-18
Density functional theory (DFT) and its time-dependent extension (TD-DFT) are powerful tools enabling the theoretical prediction of the ground- and excited-state properties of organic electronic materials with reasonable accuracy at affordable computational costs. Due to their excellent accuracy-to-numerical-costs ratio, semilocal and global hybrid functionals such as B3LYP have become the workhorse for geometry optimizations and the prediction of vibrational spectra in modern theoretical organic chemistry. Despite the overwhelming success of these out-of-the-box functionals for such applications, the computational treatment of electronic and structural properties that are of particular interest in organic electronic materials sometimes reveals severe and qualitative failures of such functionals. Important examples include the overestimation of conjugation, torsional barriers, and electronic coupling as well as the underestimation of bond-length alternations or excited-state energies in low-band-gap polymers.In this Account, we highlight how these failures can be traced back to the delocalization error inherent to semilocal and global hybrid functionals, which leads to the spurious delocalization of electron densities and an overestimation of conjugation. The delocalization error for systems and functionals of interest can be quantified by allowing for fractional occupation of the highest occupied molecular orbital. It can be minimized by using long-range corrected hybrid functionals and a nonempirical tuning procedure for the range-separation parameter.We then review the benefits and drawbacks of using tuned long-range corrected hybrid functionals for the description of the ground and excited states of π-conjugated systems. In particular, we show that this approach provides for robust and efficient means of characterizing the electronic couplings in organic mixed-valence systems, for the calculation of accurate torsional barriers at the polymer limit, and for the
Liu, Jikun; Zhao, Jiangqin; Petrochenko, Peter; Zheng, Jiwen; Hewlett, Indira
2016-12-15
In an effort to develop new tools for diagnosing influenza in resource-limited settings, we fabricated a polycarbonate (PC)-polydimethylsiloxane (PDMS) hybrid microchip using a simple epoxy silica sol-gel coating/bonding method and employed it in sensitive detection of influenza virus with Europium nanoparticles (EuNPs). The incorporation of sol-gel material in device fabrication provided functionalized channel surfaces ready for covalent immobilization of primary antibodies and a strong bonding between PDMS substrates and PC supports without increasing background fluorescence. In microchip EuNP immunoassay (µENIA) of inactivated influenza viruses, replacing native PDMS microchips with hybrid microchips allowed the achievement of a 6-fold increase in signal-to-background ratio, a 12-fold and a 6-fold decreases in limit-of-detection (LOD) in influenza A and B tests respectively. Using influenza A samples with known titers, the LOD of influenza µENIA on hybrid microchips was determined to be ~10(4) TCID50 titer/mL and 10(3)-10(4) EID50 titer/mL. A comparison test indicated that the sensitivity of influenza µENIA enhanced using the hybrid microchips even surpassed that of a commercial laboratory influenza ELISA test. In addition to the sensitivity improvement, assay variation was clearly reduced when hybrid microchips instead of native PDMS microchips were used in the µENIA tests. Finally, infectious reference viruses and nasopharyngeal swab patient specimens were successfully tested using μENIA on hybrid microchip platforms, demonstrating the potential of this unique microchip nanoparticle assay in clinical diagnosis of influenza. Meanwhile, the tests showed the necessity of using nucleic acid confirmatory tests to clarify ambiguous test results obtained from prototype or developed point-of-care testing devices for influenza diagnosis.
Pressure Correction in Density Functional Theory Calculations
Lee, S H
2008-01-01
First-principles calculations based on density functional theory have been widely used in studies of the structural, thermoelastic, rheological, and electronic properties of earth-forming materials. The exchange-correlation term, however, is implemented based on various approximations, and this is believed to be the main reason for discrepancies between experiments and theoretical predictions. In this work, by using periclase MgO as a prototype system we examine the discrepancies in pressure and Kohn-Sham energy that are due to the choice of the exchange-correlation functional. For instance, we choose local density approximation and generalized gradient approximation. We perform extensive first-principles calculations at various temperatures and volumes and find that the exchange-correlation-based discrepancies in Kohn-Sham energy and pressure should be independent of temperature. This implies that the physical quantities, such as the equation of states, heat capacity, and the Gr\\"{u}neisen parameter, estimat...
Energy Technology Data Exchange (ETDEWEB)
Pezzella, Alessandro; Capelli, Luigia [Dept. of Chemical Sciences, Via Cintia 4, 80126 Napoli (Italy); Costantini, Aniello [Dept. of Materials and Production Engineering, Piazzale Tecchio 80, 80125 Napoli (Italy); Luciani, Giuseppina, E-mail: luciani@unina.it [Dept. of Materials and Production Engineering, Piazzale Tecchio 80, 80125 Napoli (Italy); Tescione, Fabiana; Silvestri, Brigida [Dept. of Materials and Production Engineering, Piazzale Tecchio 80, 80125 Napoli (Italy); Vitiello, Giuseppe [Dept. of Chemical Sciences, Via Cintia 4, 80126 Napoli (Italy); Branda, Francesco [Dept. of Materials and Production Engineering, Piazzale Tecchio 80, 80125 Napoli (Italy)
2013-01-01
A large number of recent literature data focus on modification/modulation of surface chemistry of inorganic materials in order to improve their functional properties. Melanins, a wide class of natural pigments, are recently emerging as a powerful organic component for developing bioinspired active material for a large number of applications from organoelectronics to bioactive compounds. Here we report the use of the approach referred as 'chimie douce', involving in situ formation of the hybrids through reactions of precursors under mild conditions, to prepare novel hybrid functional architectures based on eumelanin like 5,6 dihydroxyindole-2-carboxylic acid (DHICA) polymer and TiO{sub 2}. Two synthesis procedures were carried out to get DHICA-melanin coated TiO{sub 2} nanoparticles as well as mixed DHICA/TiO{sub 2} hybrid nanostructures. Such systems were characterized through EPR, FT-IR and fluorescence spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and TEM microscopy in order to assess the effect of synthesis path as well as of DHICA content on structural, morphological and optical properties of TiO{sub 2} nanostructures. In particular, EPR, FT-IR spectra and TGA analysis confirmed the presence of DHICA-melanin in these samples. TEM measurements indicated the formation of the nanoparticles having relatively narrow size distribution with average particle size of about 10 nm. DHICA-melanin does act as a morphological agent affecting morphology of hybrid nanostructures. XRD analysis proved that TiO{sub 2} hybrid nanoparticles kept anatase structures for DHICA-melanin contents within the range of investigated compositions, i.e. up to 50% wt/wt. - Highlights: Black-Right-Pointing-Pointer TiO{sub 2}/DHICA melanin blends are novel hybrid functional architectures. Black-Right-Pointing-Pointer Two synthetic approaches were explored to produce TiO{sub 2}/DHICA nanostructures. Black-Right-Pointing-Pointer TiO{sub 2} nanorods prepared
Energy Technology Data Exchange (ETDEWEB)
Wilde, Andreas
2009-10-27
Due to the relatively low energy density of electrical energy storage devices, the control strategy of hybrid electric vehicles has to fulfil a variety of requirements in order to provide both, the availability of hybrid functions, and their efficient execution. Energy consuming functions such as electric drive or electric boost need a high amount of energy stored in the battery. On the other hand for the optimum use of the energy regeneration function a lower state of charge is preferable in order to enable storage of the kinetic energy of the vehicle in all situations, including upon deceleration from high speeds or downhill driving. These diverging requirements yield a conflict of objectives for the charging strategy of hybrid electric vehicles. This work proposes a way to overcome the restrictions on efficiency in hybrid electric vehicles without deteriorating overall driving performance by charging or discharging the traction battery, and by setting the energy management parametres according to the current and forthcoming driving situation. Specific charging and electric drive strategies are presented for various driving situations which are identified by sensors such as navigation systems, cameras or radar. Necessary sensor data fusion methods for driving situation identification are described and a modular function architecture for predictive energy management is derived that is plug-and-play compatible with a broad fleet of vehicles. In order to evaluate its potential, this work also focuses on the simulation of the energy functions and their implementation into an experimental vehicle. This allows measurements under real traffic conditions and a sensivity analysis of the main module interactions within the architecture. (orig.)
Hosseini Largani, Sekineh; Akbarzadeh Pasha, Mohammad
2016-12-01
In this research, MWCNT-ZnO hybrid nanomaterials were synthesized by a simple sol-gel process using Zn(CH3COO)2·2H2O and functionalized MWCNT with carboxyl(COOH) and hydroxyl(OH) groups. Three different mass ratios of MWCNT:ZnO = 3:1, 1:1 and 1:3 were examined. The prepared nanomaterials were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR). Successful growth of MWCNT-ZnO hybrids for both COOH and OH functional groups and all the three mass ratios were obtained. The ZnO nanoparticles attached on the surfaces of CNTs have rather spherical shapes and hexagonal crystal structure. By increasing the concentration of ZnO, the number and average size of ZnO nanoparticles decorated the body of CNTs in hybrid structures increase. By increasing the ZnO precursor, the distribution of ZnO nanoparticles that appeared on the surface of CNTs becomes more uniform. The SEM observation beside EDX analysis revealed that at the same concentration ratio the amount of ZnO loading on the surface of MWCNT-COOH is more than MWCNT-OH. Moreover, the average size of ZnO nanoparticles attached on the surface of COOH functionalized CNTs is relatively smaller than that of OH functionalized ones.
Matsubara, Masahiko; Saniz, Rolando; Partoens, Bart; Lamoen, Dirk
2017-01-01
Abstract: We investigate the role of transition metal atoms of group V-b (V, Nb, and Ta) and VI-b (Cr, Mo, and W) as n- or p-type dopants in anatase TiO2 using thermodynamic principles and density functional theory with the HeydScuseriaErnzerhof HSE06 hybrid functional. The HSE06 functional provides a realistic value for the band gap, which ensures a correct classification of dopants as shallow or deep donors or acceptors. Defect formation energies and thermodynamic transition levels are calc...
Pezzella, Alessandro; Capelli, Luigia; Costantini, Aniello; Luciani, Giuseppina; Tescione, Fabiana; Silvestri, Brigida; Vitiello, Giuseppe; Branda, Francesco
2013-01-01
A large number of recent literature data focus on modification/modulation of surface chemistry of inorganic materials in order to improve their functional properties. Melanins, a wide class of natural pigments, are recently emerging as a powerful organic component for developing bioinspired active material for a large number of applications from organoelectronics to bioactive compounds. Here we report the use of the approach referred as "chimie douce", involving in situ formation of the hybrids through reactions of precursors under mild conditions, to prepare novel hybrid functional architectures based on eumelanin like 5,6 dihydroxyindole-2-carboxylic acid (DHICA) polymer and TiO2. Two synthesis procedures were carried out to get DHICA-melanin coated TiO2 nanoparticles as well as mixed DHICA/TiO2 hybrid nanostructures. Such systems were characterized through EPR, FT-IR and fluorescence spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and TEM microscopy in order to assess the effect of synthesis path as well as of DHICA content on structural, morphological and optical properties of TiO2 nanostructures. In particular, EPR, FT-IR spectra and TGA analysis confirmed the presence of DHICA-melanin in these samples. TEM measurements indicated the formation of the nanoparticles having relatively narrow size distribution with average particle size of about 10nm. DHICA-melanin does act as a morphological agent affecting morphology of hybrid nanostructures. XRD analysis proved that TiO2 hybrid nanoparticles kept anatase structures for DHICA-melanin contents within the range of investigated compositions, i.e. up to 50% wt/wt.
Requirements for Hybrid Cosimulation
2014-08-16
hybrid cosimulation version of the Functional Mockup Interface (FMI) standard. A cosimulation standard de nes interfaces that enable diverse simulation...cosimulation standards, and specifically provides guidance for development of a hybrid cosimulation version of the Functional Mockup Interface (FMI) standard...V. Peetz, and S. Wolf. The functional mockup interface for tool independent exchange of simulation models. In Proc. of the 8-th International
Mukhopadhyay, S.; Finnis, M. W.; Harrison, N. M.
2013-03-01
Hybrid-exchange density functional theory has been used to model the electronic structure of LaCoO3. Based on a rhombohedral unit cell of R3¯c symmetry containing two Co atoms we find a mixed spin phase, comprising alternating low and high spin Co+3 ions, with a total energy at 0 K just 57 meV per formula unit above that of a nonmagnetic semiconducting ground state. In the mixed spin phase the high-spin Co+3 ions have spin moments of 3.1μB and the state is insulating with a band gap of 2.2 eV. Our calculations suggest that the effective on-site Coulomb repulsion energy Ueff on Co+3 ions is spin dependent. The Ueff on Co+3 ions is 7.1 eV and 8.5 eV for the nonmagnetic ground state and for the magnetic high spin state, respectively. For the mixed spin state, two different Ueff are estimated for two Co+3 ions in the unit cell having different spin states, 8.0 eV for the high-spin Co+3 ion and 7.0 eV for the low-spin Co+3 ion. An estimate of the harmonic phonon free energy suggests that this mixed spin phase would become the more stable phase as the temperature increases, which is consistent with experimental evidence. An alternative intermediate spin state is higher in energy at all temperatures.
Collins, P.J.
2005-01-01
In this paper, we present a general framework for describing and studying hybrid systems. We represent the trajectories of the system as functions on a hybrid time domain, and the system itself by its trajectory space, which is the set of all possible trajectories. The trajectory space is given a na
Assessment of density functional methods with correct asymptotic behavior
Tsai, Chen-Wei; Li, Guan-De; Chai, Jeng-Da
2012-01-01
Long-range corrected (LC) hybrid functionals and asymptotically corrected (AC) model potentials are two distinct density functional methods with correct asymptotic behavior. They are known to be accurate for properties that are sensitive to the asymptote of the exchange-correlation potential, such as the highest occupied molecular orbital energies and Rydberg excitation energies of molecules. To provide a comprehensive comparison, we investigate the performance of the two schemes and others on a very wide range of applications, including the asymptote problems, self-interaction-error problems, energy-gap problems, charge-transfer problems, and many others. The LC hybrid scheme is shown to consistently outperform the AC model potential scheme. In addition, to be consistent with the molecules collected in the IP131 database [Y.-S. Lin, C.-W. Tsai, G.-D. Li, and J.-D. Chai, J. Chem. Phys. 136, 154109 (2012)], we expand the EA115 and FG115 databases to include, respectively, the vertical electron affinities and f...
Timón, V; Praveen, C S; Escamilla-Roa, E; Valant, M
2013-07-01
A hybrid density functional based study of a phyllosilicate (PS) is presented here for the first time. Using all-electron electronic structure calculations with the B3LYP hybrid functional, we have investigated the electronic and structural properties of a series of trioctahedral 1M-polytype K-bearing micas starting from phlogopite (the Mg-end member), ending with the annite (the Fe-end member), and passing through the biotite (a solid solution of the end members). Electronic band gap is calculated for all the compositions and nature of the electronic transition is discussed with the aid of band structure and density of states plots. An excellent agreement with the available experimental data has been observed. An insulator to semiconductor transition is explained on the basis of orbital hybridization. A further comparison is made using the pure GGA functional. For the completeness of the study, the dielectric properties of phlogopite are calculated using the coupled perturbed Kohn-Sham scheme, as implemented within the CRYSTAL09 code.
Wang, Tingting; Chen, Yihui; Ma, Junfeng; Chen, Mingliang; Nie, Chenggang; Hu, Minjie; Li, Ying; Jia, Zhijian; Fang, Jianghua; Gao, Haoqi
2013-09-20
A novel sorbent for solid-phase extraction (SPE) was synthesized by chemical immobilization of ampholine on hybrid organic-inorganic silica material. The ampholine-functionalized hybrid organic-inorganic silica sorbent is consisted of aliphatic amine groups, carboxyl groups and long carbon chains, allowing for extraction of both acidic and basic compounds. The retention properties of the developed sorbent were evaluated for 1-hydroxy-2-naphthoic acid (HNA), 1-naphthoic acid (NA), 3-hydroxybenzoic acid (HBA), benzoic acid (BA), sorbic acid (SA), vanillic aldehyde (VA), butyl 4-hydroxybenzoate (BHB), propyl 4-hydroxybenzoate (PHB), ethyl 4-hydroxybenzoate (EHB), and methyl 4-hydroxybenzoate (MHB). The results show that such a sorbent has three types of interaction, i.e., electrostatic interaction, hydrophobic interaction, and hydrogen bonding, exhibiting high extraction efficiency towards the compounds tested. The adsorption capacities of the analytes ranged from 0.61 to 6.54μgmg(-1). The reproducibility of the sorbent preparation was evaluated at three spiking concentration levels, with relative standard deviations (RSDs) of 1.0-10.5%. The recoveries of ten acidic and basic compounds spiked in beverage Coca-Cola(®) sample ranged from 82.5% to 98.2% with RSDs less than 5.8%. Under optimum conditions, the ampholine-functionalized hybrid organic-inorganic silica sorbent rendered higher extraction efficiency for acidic compounds than that of the commercially available ampholine-functionalized silica particles, and was comparable to that of the commercial Oasis WAX and Oasis WCX.
Lee, Noo Ri; Yoon, Na Young; Jung, Minyoung; Kim, Ji-Yun; Seo, Seong Jun; Wang, Hye-Young; Lee, Hyeyoung; Sohn, Young Bae; Choi, Eung Ho
2016-08-01
X-linked ichthyosis (XLI) is a recessively inherited ichthyosis. Skin barrier function of XLI patients reported in Western countries presented minimally abnormal or normal. Here, we evaluated the skin barrier properties and a skin barrier-related gene mutation in 16 Korean XLI patients who were diagnosed by fluorescence in situ hybridization and array comparative genomic hybridization analysis. Skin barrier properties were measured, cytokine expression levels in the stratum corneum (SC) were evaluated with the tape stripped specimen from skin surface, and a genetic test was done on blood. XLI patients showed significantly lower SC hydration, but normal basal trans-epidermal water loss and skin surface pH as compared to a healthy control group. Histopathology of ichthyosis epidermis showed no acanthosis, and levels of the pro-inflammatory cytokines in the corneal layer did not differ between control and lesional/non-lesional skin of XLI patients. Among the mutations in filaggrin (FLG), kallikrein 7 (KLK7), and SPINK5 genes, the prevalence of KLK7 gene mutations was significantly higher in XLI patients (50%) than in controls (0%), whereas FLG and SPINK5 prevalence was comparable. Korean XLI patients exhibited unimpaired skin barrier function and frequent association with the KLK7 gene polymorphism, which may differentiate them from Western XLI patients.
Azpiroz, Jon M; Ugalde, Jesus M; Infante, Ivan
2014-01-14
In this work, we build a benchmark data set of geometrical parameters, vibrational normal modes, and low-lying excitation energies for MX quantum dots, with M = Cd, Zn, and X = S, Se, Te. The reference database has been constructed by ab initio resolution-of-identity second-order approximate coupled cluster RI-CC2/def2-TZVPP calculations on (MX)6 model molecules in the wurtzite structure. We have tested 26 exchange-correlation density functionals, ranging from local generalized gradient approximation (GGA) and hybrid GGA to meta-GGA, meta-hybrid, and long-range corrected. The best overall functional is the hybrid PBE0 that outperforms all other functionals, especially for excited state energies, which are of particular relevance for the systems studied here. Among the DFT methodologies with no Hartree-Fock exchange, the M06-L is the best one. Local GGA functionals usually provide satisfactory results for geometrical structures and vibrational frequencies but perform rather poorly for excitation energies. Regarding the CdSe cluster, we also present a test of several basis sets that include relativistic effects via effective core potentials (ECPs) or via the ZORA approximation. The best basis sets in terms of computational efficiency and accuracy are the SBKJC and def2-SV(P). The LANL2DZ basis set, commonly employed nowadays on these types of nanoclusters, performs very disappointingly. Finally, we also provide some suggestions on how to perform calculations on larger systems keeping a balance between computational load and accuracy.
Institute of Scientific and Technical Information of China (English)
刘小君; 王宁; 程浩
2011-01-01
用含时密度泛函方法研究了具有推拉结构的有机发光材料3-(二氰亚甲基)-5,5-二甲基-1-(4-[9-咔唑基]-苯乙烯基)环己烯(DCDCC)的吸收和荧光光谱,并考虑了溶剂效应.通过与实验光谱的比较,重点评价了包括局域和长程在内的8种交换泛函.结果表明泛函的选择对结果的可靠性至关重要,在密度泛函和含时密度泛函理论框架下,包含44%Hartree Fock交换泛函的BMK杂化函数联同连续极化模型和中等大小的基组最适合研究DCDCC分子的光谱性质.此外,尽管DCDCC分子内电荷转移并没有强致发出双荧光,但仍然可以用平面分子内电荷转移和扭转分子内电荷转移模型解释DCDCC激发态的结构.BMK泛函计算的结果表明DCDCC的激发态结构支持平面分子内电荷转移模型.%The absorption and fluorescence spectra of 3-(dicyanomethylene)-5,5-dimethyl-1-(4-[9-carbazol]-styryl)cyclohexene (DCDCC), an organic light emitting material with pull-push structure, were investigated using a time-dependent density functional theory (TD-DFT) approach and bulk solvent effects were taken into account. The performance of eight exchange-correlation functionals including both local and long-range hybrids was assessed by comparing the calculated electron transition energies to experimental observations. It turns out that the appropriate choice of functionals is crucial to obtain an accurate value and BMK hybrids, which contain 44% Hartree Fock exchange, in the frame of DFT and TD-DFT with the polarizable continuum model and a medium sized basis set, emerges as an effective strategy for DCDCC. Moreover, the planar and twisted intramolecular charge transfer (PICT and TICT)models were used to interpret the excited state structure of DCDCC although the charge transfer character of the excited-state was not as intense as to emit obvious double fluorescence. The accurate structures were optimized by BMK and supported the PICT model.
Page, P R
2003-01-01
We review the status of hybrid baryons. The only known way to study hybrids rigorously is via excited adiabatic potentials. Hybrids can be modelled by both the bag and flux-tube models. The low-lying hybrid baryon is N 1/2^+ with a mass of 1.5-1.8 GeV. Hybrid baryons can be produced in the glue-rich processes of diffractive gamma N and pi N production, Psi decays and p pbar annihilation.
Kesharwani, Manoj K; Brauer, Brina; Martin, Jan M L
2015-03-05
We have obtained uniform frequency scaling factors λ(harm) (for harmonic frequencies), λ(fund) (for fundamentals), and λ(ZPVE) (for zero-point vibrational energies (ZPVEs)) for the Weigend-Ahlrichs and other selected basis sets for MP2, SCS-MP2, and a variety of DFT functionals including double hybrids. For selected levels of theory, we have also obtained scaling factors for true anharmonic fundamentals and ZPVEs obtained from quartic force fields. For harmonic frequencies, the double hybrids B2PLYP, B2GP-PLYP, and DSD-PBEP86 clearly yield the best performance at RMSD = 10-12 cm(-1) for def2-TZVP and larger basis sets, compared to 5 cm(-1) at the CCSD(T) basis set limit. For ZPVEs, again, the double hybrids are the best performers, reaching root-mean-square deviations (RMSDs) as low as 0.05 kcal/mol, but even mainstream functionals like B3LYP can get down to 0.10 kcal/mol. Explicitly anharmonic ZPVEs only are marginally more accurate. For fundamentals, however, simple uniform scaling is clearly inadequate.
Quantum electrostatic surface waves in a hybrid plasma waveguide: Effect of nano-sized slab
Shahmansouri, M.; Mahmodi Moghadam, M.
2017-10-01
The propagation properties of surface plasmon (SP) waves are studied in a hybrid plasma waveguide (consisting of plasma-gap-dielectric layers) with quantum effects including the Fermi-pressure, the Bohm potential and the exchange-correlation interaction. By using a quantum hydrodynamic model and Maxwell's equations, the dispersion relation of SP waves is derived, which describes the quantum corrected features of the dispersion properties of such surface waves. Previous results in this context are recovered. It is found that the exchange-correlation interactions and the presence of the second dielectric layer drastically modify the behaviors of the surface plasmon waves. The implications of our finding are discussed in some particular cases of interest. Our finding is applicable for understanding the surface wave behaviors in nano-scale systems.
Energy Technology Data Exchange (ETDEWEB)
Barbu, Eugen; Tsibouklis, John [School of Pharmacy and Biomedical Sciences, University of Portsmouth, St Michael' s Building, White Swan Road, Portsmouth PO1 2DT (United Kingdom); Verestiuc, Liliana [Faculty of Medical Bioengineering, University of Medicine and Pharmacy ' Gr T Popa' , 9-13 Kogalniceanu Street, Iasi, 700454 (Romania); Iancu, Mihaela; Jatariu, Anca [Faculty of Chemical Engineering and Environmental Protection, Technical University' Gh Asachi' , Boulevard Mangeron, 71A, 700100, Iasi (Romania); Lungu, Adriana [Faculty of Applied Chemistry and Materials Science, Polytechnic University of Bucharest, Polizu Street 1-7, 011061, Bucharest (Romania)], E-mail: eugen@barbu@port.ac.uk
2009-06-03
Nanoparticulate hybrid polymeric hydrogels (10-70 nm) have been obtained via the radical-induced co-polymerization of acrylic acid-functionalized chitosan with either N-isopropylacrylamide or 2-hydroxyethyl methacrylate, and the materials have been investigated for their ability to act as controlled release vehicles in ophthalmic drug delivery. Studies on the effects of network structure upon swelling properties, adhesiveness to substrates that mimic mucosal surfaces and biodegradability, coupled with in vitro drug release investigations employing ophthalmic drugs with differing aqueous solubilities, have identified nanoparticle compositions for each of the candidate drug molecules. The hybrid nanoparticles combine the temperature sensitivity of N-isopropylacrylamide or the good swelling characteristics of 2-hydroxyethyl methacrylate with the susceptibility of chitosan to lysozyme-induced biodegradation.
Guseinov, Israfil I; Sahin, Ercan
2011-04-01
By the use of ellipsoidal coordinates, the two-center Coulomb and hybrid integrals over complete orthonormal sets of Ψα-ETO exponential type orbitals arising in ab initio calculations of molecules are evaluated, where α = 1,0, -1, -2, ...,. These integrals are expressed through the auxiliary functions Q(ns)(q) and G(-ns)(q). The comparison is made with some values of integrals for Slater type orbitals the computation results of which are in good agreement with those obtained in the literature. The relationships obtained are valid for the arbitrary quantum numbers, screening constants and location of orbitals. Closed form expressions for two-center Coulomb and hybrid integrals for 1s and 2s orbitals with α = 1 are also presented. As an example of application, the Hartree-Fock-Roothaan calculations for the ground state of H(2) molecule are carried out with α = 1 and α = 0.
Chan, Bun; Radom, Leo
2011-09-13
A variety of combinations of B-LYP-based double-hybrid density functional theory (DHDFT) procedures and basis sets have been examined. A general observation is that the optimal combination of exchange contributions is in the proximity of 30% Becke 1988 (B88) exchange and 70% Hartree-Fock (HF) exchange, while for the correlation contributions, the use of independently optimized spin-component-scaled Møller-Plesset second-order perturbation theory (SCS-MP2) parameters (MP2OS and MP2SS) is beneficial. The triple-ζ Dunning aug'-cc-pVTZ+d and Pople 6-311+G(3df,2p)+d basis sets are found to be cost-effective for DHDFT methods. As a result, we have formulated the DuT-D3 DHDFT procedure, which employs the aug'-cc-pVTZ+d basis set and includes 30% B88 and 70% HF exchange energies, 59% LYP, 47% MP2OS, and 36% MP2SS correlation energies, and a D3 dispersion correction with the parameters s6 = 0.5, sr,6 = 1.569, and s8 = 0.35. Likewise, the PoT-D3 DHDFT procedure was formulated with the 6-311+G(3df,2p)+d basis set and has 32% B88 and 68% HF exchange energies, 63% LYP, 46% MP2OS, and 27% MP2SS correlation energies, and the D3 parameters s6 = 0.5, sr,6 = 1.569, and s8 = 0.30. Testing using the large E3 set of 740 energies demonstrates the robustness of these methods. Further comparisons show that the performance of these methods, particularly DuT-D3, compares favorably with the previously reported DSD-B-LYP and DSD-B-LYP-D3 methods used in conjunction with quadruple-ζ aug'-pc3+d and aug'-def2-QZVP basis sets but at lower computational expense. The previously reported ωB97X-(LP)/6-311++G(3df,3pd) procedure also performs very well. Our findings highlight the cost-effectiveness of appropriate- and moderate-sized triple-ζ basis sets in the application of DHDFT procedures.
Mazzio, Katherine A; Okamoto, Ken; Li, Zhi; Gutmann, Sebastian; Strein, Elisabeth; Ginger, David S; Schlaf, Rudy; Luscombe, Christine K
2013-02-14
A one pot method for organic/colloidal CdSe nanoparticle hybrid material synthesis is presented. Relative to traditional ligand exchange processes, these materials require smaller amounts of the desired capping ligand, shorter syntheses and fewer processing steps, while maintaining nanoparticle morphology.
Energy Technology Data Exchange (ETDEWEB)
Gaemperli, Oliver [University Hospital Zurich, Cardiac Imaging, Zurich (Switzerland); University Hospital Zurich, Nuclear Cardiology, Cardiovascular Center, Zurich (Switzerland); Kaufmann, Philipp A. [University Hospital Zurich, Cardiac Imaging, Zurich (Switzerland); Alkadhi, Hatem [University Hospital Zurich, Institute of Diagnostic and Interventional Radiology, Zurich (Switzerland)
2014-05-15
Hybrid cardiac single photon emission computed tomography (SPECT)/CT imaging allows combined assessment of anatomical and functional aspects of cardiac disease. In coronary artery disease (CAD), hybrid SPECT/CT imaging allows detection of coronary artery stenosis and myocardial perfusion abnormalities. The clinical value of hybrid imaging has been documented in several subsets of patients. In selected groups of patients, hybrid imaging improves the diagnostic accuracy to detect CAD compared to the single imaging techniques. Additionally, this approach facilitates functional interrogation of coronary stenoses and guidance with regard to revascularization procedures. Moreover, the anatomical information obtained from CT coronary angiography or coronary artery calcium scores (CACS) adds prognostic information over perfusion data from SPECT. The use of cardiac hybrid imaging has been favoured by the dissemination of dedicated hybrid systems and the release of dedicated image fusion software, which allow simple patient throughput for hybrid SPECT/CT studies. Further technological improvements such as more efficient detector technology to allow for low-radiation protocols, ultra-fast image acquisition and improved low-noise image reconstruction algorithms will be instrumental to further promote hybrid SPECT/CT in research and clinical practice. (orig.)
Bulk Properties of Transition Metals: A Challenge for the Design of Universal Density Functionals.
Janthon, Patanachai; Luo, Sijie Andy; Kozlov, Sergey M; Viñes, Francesc; Limtrakul, Jumras; Truhlar, Donald G; Illas, Francesc
2014-09-09
Systematic evaluation of the accuracy of exchange-correlation functionals is essential to guide scientists in their choice of an optimal method for a given problem when using density functional theory. In this work, accuracy of one Generalized Gradient Approximation (GGA) functional, three meta-GGA functionals, one Nonseparable Gradient Approximation (NGA) functional, one meta-NGA, and three hybrid GGA functionals was evaluated for calculations of the closest interatomic distances, cohesive energies, and bulk moduli of all 3d, 4d, and 5d bulk transition metals that have face centered cubic (fcc), hexagonal closed packed (hcp), or body centered cubic (bcc) structures (a total of 27 cases). Our results show that including the extra elements of kinetic energy density and Hartree-Fock exchange energy density into gradient approximation density functionals does not usually improve them. Nevertheless, the accuracies of the Tao-Perdew-Staroverov-Scuseria (TPSS) and M06-L meta-GGAs and the MN12-L meta-NGA approach the accuracy of the Perdew-Burke-Ernzerhof (PBE) GGA, so usage of these functionals may be advisable for systems containing both solid-state transition metals and molecular species. The N12 NGA functional is also shown to be almost as accurate as PBE for bulk transition metals, and thus it could be a good choice for studies of catalysis given its proven good performance for molecular species.
Zheng, Zilong
2016-06-24
Density functional theory (DFT) approaches based on range-separated hybrid functionals are currently methods of choice for the description of the charge-transfer (CT) states in organic donor/acceptor solar cells. However, these calculations are usually performed on small-size donor/acceptor complexes and as result do not account for electronic polarization effects. Here, using a pentacene/C60 complex as a model system, we discuss the ability of long-range corrected (LCR) hybrid functionals in combination with the polarizable continuum model (PCM) to determine the impact of the solid-state environment on the CT states. The CT energies are found to be insensitive to the interactions with the dielectric medium when a conventional time-dependent DFT/PCM (TDDFT/PCM) approach is used. However, a decrease in the energy of the CT state in the framework of LRC functionals can be obtained by using a smaller range-separated parameter when going from an isolated donor/acceptor complex to the solid-state case.
Dziedzic, J; Hill, Q; Skylaris, C-K
2013-12-07
We present a method for the calculation of four-centre two-electron repulsion integrals in terms of localised non-orthogonal generalised Wannier functions (NGWFs). Our method has been implemented in the ONETEP program and is used to compute the Hartree-Fock exchange energy component of Hartree-Fock and Density Functional Theory (DFT) calculations with hybrid exchange-correlation functionals. As the NGWFs are optimised in situ in terms of a systematically improvable basis set which is equivalent to plane waves, it is possible to achieve large basis set accuracy in routine calculations. The spatial localisation of the NGWFs allows us to exploit the exponential decay of the density matrix in systems with a band gap in order to compute the exchange energy with a computational effort that increases linearly with the number of atoms. We describe the implementation of this approach in the ONETEP program for linear-scaling first principles quantum mechanical calculations. We present extensive numerical validation of all the steps in our method. Furthermore, we find excellent agreement in energies and structures for a wide variety of molecules when comparing with other codes. We use our method to perform calculations with the B3LYP exchange-correlation functional for models of myoglobin systems bound with O2 and CO ligands and confirm that the same qualitative behaviour is obtained as when the same myoglobin models are studied with the DFT+U approach which is also available in ONETEP. Finally, we confirm the linear-scaling capability of our method by performing calculations on polyethylene and polyacetylene chains of increasing length.
Fractional-charge and fractional-spin errors in range-separated density-functional theory
Mussard, Bastien
2016-01-01
We investigate fractional-charge and fractional-spin errors in range-separated density-functional theory. Specifically, we consider the range-separated hybrid (RSH) method which combines long-range Hartree-Fock (HF) exchange with a short-range semilocal exchange-correlation density functional, and the RSH+MP2 method which adds long-range second-order M{{\\o}}ller-Plesset (MP2) correlation. Results on atoms and molecules show that the fractional-charge errors obtained in RSH are much smaller than in the standard Kohn-Sham (KS) scheme applied with semilocal or hybrid approximations, and also generally smaller than in the standard HF method. The RSH+MP2 method tends to have smaller fractional-charge errors than standard MP2 for the most diffuse systems, but larger fractional-charge errors for the more compact systems. Even though the individual contributions to the fractional-spin errors in the H atom coming from the short-range exchange and correlation density-functional approximations are smaller than the corre...
Deng, Lijuan; Guo, Wenshan; Ngo, Huu Hao; Zhang, Xinbo; Wang, Xiaochang C; Zhang, Qionghua; Chen, Rong
2016-05-01
In this study, new sponge modified plastic carriers for moving bed biofilm reactor (MBBR) was developed. The performance and membrane fouling behavior of a hybrid MBBR-membrane bioreactor (MBBR-MBR) system were also evaluated. Comparing to the MBBR with plastic carriers (MBBR), the MBBR with sponge modified biocarriers (S-MBBR) showed better effluent quality and enhanced nutrient removal at HRTs of 12h and 6h. Regarding fouling issue of the hybrid systems, soluble microbial products (SMP) of the MBR unit greatly influenced membrane fouling. The sponge modified biocarriers could lower the levels of SMP in mixed liquor and extracellular polymeric substances in activated sludge, thereby mitigating cake layer and pore blocking resistances of the membrane. The reduced SMP and biopolymer clusters in membrane cake layer were also observed. The results demonstrated that the sponge modified biocarriers were capable of improving overall MBBR performance and substantially alleviated membrane fouling of the subsequent MBR unit.
Yang, Xiaohui
2012-01-01
Traditional materials for application in organic light emitting diodes (OLEDs) are primarily based on small molecules and polymers, with much fewer examples of intermediate molecular weight materials. Our interest lies in this intermediate molecular weight range, specifically in hybrids based on 3-dimensional silsesquioxane (SSQ) cores that represents a new class of versatile materials for application in solution processable OLEDs. We report here various SSQ based hybrids that are easily prepared in one high-yield step from the Heck coupling of commercially available 1-bromopyrene, and 1-bromo-4-heptylbenzene with octavinyl-T8-SSQ, and a mixture of octavinyl-T8-, decavinyl-T10- and dodecavinyl-T12-SSQ. The resulting materials offer numerous advantages for OLEDs including amorphous properties, high-glass-transition temperatures (T g), low polydispersity, solubility in common solvents, and high purity via column chromatography. Solution processed OLEDs prepared from the SSQ hybrids provide sky-blue emission with external quantum efficiencies and current efficiencies of 3.64% and 9.56 cd A -1 respectively. © 2012 The Royal Society of Chemistry.
Qu, Jiuhui; Zhao, Xu
2008-07-01
P-N hybrid electrode of boron-doped diamond (BDD) and TiO2 were designed and fabricated via selective deposition of TiO2 onto BDD electrode. This hybrid electrode exhibit high photoelectrocatalytic activities toward degradation of acid orange II (AOII) and 2, 4-dichloropheonl (2,4-DCP) due to the P-N effect and high electrocatalytic and photocatalytic activities of BDD electrode and TiO2 particles. The structures of TiO2 and BDD were confirmed by Raman spectra analysis. Atom force microscopy and scanning electron microscopy showed that the TiO2 deposits consist of adherent nanomicro-sized particles, scattered on the BDD substrate. AOII and 2,4-DCP in a solution can be efficiently degraded at the hybrid electrode in the photoelectrocatalysis (PEC) process. Effect of applied bias potentials and solution pH values on AOII and 2,4-DCP degradation were investigated. In the electro-oxidation process, some intermediates such as phenols were detected and they accumulated with the reaction evolution based on the analysis of UV-vis and GC-MS variation. By contrast, phenols intermediates will be degraded with the reaction evolution in the photoelectrocatalysis process. And, organic aromatic and aliphatic carboxylic acids were detected. Furthermore, different degradation mechanism of AOII and 2,4-DCP in the electro-oxidation, photocatalysis, and photoelectrocatalysis is proposed.
LDA + U and hybrid functional calculations for defects in ZnO, SnO{sub 2}, and TiO{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Janotti, Anderson; Van de Walle, Chris G. [Materials Department, University of California, Santa Barbara, CA 93106-5050 (United States)
2011-04-15
We describe and compare defect calculations based on density functional theory within the local density approximation (LDA), the orbital-dependent LDA + U, and using hybrid functionals. Limitations of the LDA in describing defect formation energies and transition levels are discussed, followed by corrections based on the LDA + U, and the use of the hybrid functional of Heyd, Scuseria, and Ernzerhof (HSE). The band-gap error in LDA leads to large uncertainties not only in defect transition levels but also in formation energies. LDA + U provides a partial correction to the band gap and, when combined with LDA, provides an accurate method for predicting transition levels. Formation energies obtained from the LDA + U/LDA approach depend on the ability of LDA + U to correctly describe the position of the band edges on an absolute energy scale. Although computationally demanding, HSE is demonstrated to be a reliable method for predicting structure and electronic properties of semiconductors, including transition levels and formation energies of defects. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Hu, F M; Sun, C P; Zhou, L; Shi, Tao; Zhou, Lan
2006-01-01
This is the first one of a series of our papers theoretically studying the coherent control of photon transmission along the coupled resonator optical waveguide (CROW) by doping artificial atoms for various hybrid structures. We will provide the several approaches correspondingly based on Green function, the mean field method and spin wave theory et al. In the present paper we adopt the two-time Green function approach to study the coherent transmission photon in a CROW with homogeneous couplings, each cavity of which is doped by a two-level artificial atom. We calculate the two-time correlation function for photon in the weak-coupling case. Its poles predict the exact dispersion relation, which results in the group velocity coherently controlled by the collective excitation of the doping atoms. We emphasize the role of the population inversion of doping atoms induced by some polarization mechanism.
Energy Technology Data Exchange (ETDEWEB)
West, J.G.W. [Electrical Machines (United Kingdom)
1997-07-01
The reasons for adopting hybrid vehicles result mainly from the lack of adequate range from electric vehicles at an acceptable cost. Hybrids can offer significant improvements in emissions and fuel economy. Series and parallel hybrids are compared. A combination of series and parallel operation would be the ideal. This can be obtained using a planetary gearbox as a power split device allowing a small generator to transfer power to the propulsion motor giving the effect of a CVT. It allows the engine to run at semi-constant speed giving better fuel economy and reduced emissions. Hybrid car developments are described that show the wide range of possible hybrid systems. (author)
DEFF Research Database (Denmark)
Han, Zhong Hua; Goertz, Stefan; Zimmermann, Ralf
2013-01-01
Variable-fidelity surrogate modeling offers an efficient way to generate aerodynamic data for aero-loads prediction based on a set of CFD methods with varying degree of fidelity and computational expense. In this paper, direct Gradient-Enhanced Kriging (GEK) and a newly developed Generalized Hybrid...... for the aerodynamic coefficients and drag polar of an RAE 2822 airfoil. It is shown that the gradient-enhanced GHBF proposed in this paper is very promising and can be used to significantly improve the efficiency, accuracy and robustness of VFM in the context of aero-loads prediction. © 2012 Elsevier Masson SAS. All...
Institute of Scientific and Technical Information of China (English)
徐治
2015-01-01
The Visual C++ and MATLAB hybrid programming technique uses VC++ as the powerful software development tool, and directly calls the immense MATLAB algorithm function library while implementing a sophisti-cated algorithm. This approach can achieve the complementation of merits and greatly reduce the coding time of so-phisticated algorithm. This paper introduces the principle of hybrid programming, then details the MATLAB compiler based techniques of coding and project configuration which calls MATLAB function library from VC++.%Visual C++与MATLAB的混合编程技术是以VC++作为强有力的软件开发工具，而在实现复杂算法时则直接调用MATLAB涵盖很广的算法函数库。这种方式可以做到优势互补，大大减少复杂算法的编码时间。本文介绍了混合编程的基本原理，并详细介绍了基于MATLAB编译器的VC++调用MATLAB函数库的代码编写及项目配置等方面的技术。
El Mrabet, R.; Kassou, S.; Tahiri, O.; Belaaraj, A.; Guionneau, P.
2016-10-01
In the current study, a combination between theoretical and experimental studies has been made for the hybrid perovskite [NH3-(CH2)10-NH3]ZnCl4. The density functional theory (DFT) was performed to investigate structural and electronic properties of the tilted compound. A local approximation (LDA) and semi-local approach (GGA) were employed. The results are obtained using, respectively, the local exchange correlation functional of Perdew-Wang 92 (PW92) and semi local functional of Perdew-Burke-Ernzerhof (PBE). The optimized cell parameters are in good agreement with the experimental results. Electronic properties have been studied through the calculation of band structures and density of state (DOS), while structural properties are investigated by geometry optimization of the cell. Fritz-Haber-Institute (FHI) pseudopotentials were employed to perform all calculations. The optical diffuse reflectance spectra was mesured and applied to deduce the refractive index ( n), the extinction coefficient ( k), the absorption coefficient (α), the real and imaginary dielectric permittivity parts (ɛr,ɛi)) and the optical band gap energy Eg. The optical band gap energy value shows good consistent with that obtained from DFT calculations and reveals the insulating behavior of the material.
Deb, Anish; Sarkar, Gautam
2016-01-01
This book introduces a new set of orthogonal hybrid functions (HF) which approximates time functions in a piecewise linear manner which is very suitable for practical applications. The book presents an analysis of different systems namely, time-invariant system, time-varying system, multi-delay systems---both homogeneous and non-homogeneous type- and the solutions are obtained in the form of discrete samples. The book also investigates system identification problems for many of the above systems. The book is spread over 15 chapters and contains 180 black and white figures, 18 colour figures, 85 tables and 56 illustrative examples. MATLAB codes for many such examples are included at the end of the book.
Directory of Open Access Journals (Sweden)
van der Veen Hugo C
2012-09-01
Full Text Available Abstract Background Aseptic loosening of total hip arthroplasties is generally caused by periprosthetic bone resorption due to tissue reactions on polyethylene wear particles. In vitro testing of polyethylene cups incorporated with vitamin E shows increased wear resistance. The objective of this study is to compare vitamin E-stabilized highly cross-linked polyethylene with conventional cross-linked polyethylene in “reversed hybrid” total hip arthroplasties (cemented all-polyethylene cups combined with uncemented femoral stems. We hypothesize that the adjunction of vitamin E leads to a decrease in polyethylene wear in the long-term. We also expect changes in bone mineral density, less osteolysis, equal functional scores and increased implant survival in polyethylene cemented cups incorporated with vitamin E in the long-term. Design A double-blinded randomized controlled trial will be conducted. Patients to be included are aged under 70, suffer from non-inflammatory degenerative joint disease of the hip and are scheduled for a primary total hip arthroplasty. The study group will receive a reversed hybrid total hip arthroplasty with a vitamin E-stabilized highly cross-linked polyethylene cemented cup. The control group will receive a reversed hybrid total hip arthroplasty with a conventional cross-linked polyethylene cemented cup. Radiological follow-up will be assessed at 6 weeks and at 1, 3, 5, 7 and 10 years postoperatively, to determine polyethylene wear and osteolysis. Patient-reported functional status (HOOS, physician-reported functional status (Harris Hip Score and patients’ physical activity behavior (SQUASH will also be assessed at these intervals. Acetabular bone mineral density will be assessed by dual energy X-ray absorptiometry (DEXA at 6 weeks and at 1 year and 2 years postoperatively. Implant survival will be determined at 10 years postoperatively. Discussion In vitro results of vitamin E-stabilized polyethylene are promising
Peng, Mao; Qi, Ji; Zhou, Zhi; Liao, Zhangjie; Zhu, Zhongming; Guo, Honglei
2010-08-17
A facile method for constructing superhydrophobic, conductive, and transparent/translucent coatings is presented. Pristine multiwalled carbon nanotubes (MWNTs) are first noncovalently (wrapped) modified by an organic-inorganic hybrid of an amphiphilic copolymer of styrene and maleic anhydride and silica with the existence of gamma-aminopropyltriethoxysilane (a silane coupling agent). The modified MWNTs were mixed with tetraethyl orthosilicate in ethanol, air sprayed, coated with a fluoroalkylsilane, and then heat treated to obtain the superhydrophobic, conductive, and transparent/translucent coatings. Scanning electron microscopy shows that the coatings have a micrometer- and nanometer-scale hierarchical structure similar to that of lotus leaves; therefore, they show both high water contact angles (>160 degrees) and low sliding angles (coatings also exhibit good transmittance and greatly improved conductivities. This method is convenient, inexpensive, and easy to scale up. Moreover, it does not require any chemical modification of the MWNTs or use any harsh chemicals.
Zhang, Cong-yun; Hao, Rui; Zhao, Bin; Hao, Yao-wu; Liu, Ya-qing
2017-07-01
The graphene-mediated surface enhanced Raman scattering (SERS) substrates by virtues of plasmonic metal nanostructures and graphene or its derivatives have attracted tremendous interests which are expected to make up the deficiency of traditional plasmonic metal substrates. Herein, we designed and fabricated a novel ternary Ag@GO@Au sandwich hybrid wherein the ultrathin graphene oxide (GO) films were seamlessly wrapped around the hierarchical flower-like Ag particle core and meanwhile provided two-dimensional anchoring scaffold for the coating of Au nanoparticles (NPs). The surface coverage density of loading Au NPs could be readily controlled by tuning the dosage amount of Au particle solutions. These features endowed the sandwiched structures high enrichment capability for analytes such as aromatic molecules and astonishing SERS performance. The Raman signals were enormously enhanced with an ultrasensitive detection limit of rhodamine-6G (R6G) as low as 10-13 M based on the chemical enhancement from GO and multi-dimensional plasmonic coupling between the metal nanoparticles. In addition, the GO interlayer as an isolating shell could effectively prevent the metal-molecule direct interaction and suppress the oxidation of Ag after exposure at ambient condition which enabled the substrates excellent reproducibility with less than 6% signal variations and prolonged life-time. To evaluate the feasibility and the practical application for SERS detection in real-world samples based on GO sandwiched hybrid as SERS-active substrate, three different prohibited colorants with a series of concentrations were measured with a minimum detected concentration down to 10-9 M. Furthermore, the prepared GO sandwiched nanostructures can be used to identify different types of colorants existing in red wine, implying the great potential applications for single-particle SERS sensing of biotechnology and on-site monitoring in food security.
Mardirossian, Narbe; Head-Gordon, Martin
2016-06-01
A combinatorially optimized, range-separated hybrid, meta-GGA density functional with VV10 nonlocal correlation is presented. The final 12-parameter functional form is selected from approximately 10 × 109 candidate fits that are trained on a training set of 870 data points and tested on a primary test set of 2964 data points. The resulting density functional, ωB97M-V, is further tested for transferability on a secondary test set of 1152 data points. For comparison, ωB97M-V is benchmarked against 11 leading density functionals including M06-2X, ωB97X-D, M08-HX, M11, ωM05-D, ωB97X-V, and MN15. Encouragingly, the overall performance of ωB97M-V on nearly 5000 data points clearly surpasses that of all of the tested density functionals. In order to facilitate the use of ωB97M-V, its basis set dependence and integration grid sensitivity are thoroughly assessed, and recommendations that take into account both efficiency and accuracy are provided.
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.
Juarez-Hernandez, Leon J; Cornella, Nicola; Pasquardini, Laura; Battistoni, Silvia; Vidalino, Laura; Vanzetti, Lia; Caponi, Silvia; Dalla Serra, Mauro; Iannotta, Salvatore; Pederzolli, Cecilia; Macchi, Paolo; Musio, Carlo
2016-01-01
The interfacing of artificial devices with biological systems is a challenging field that crosses several disciplines ranging from fundamental research (biophysical chemistry, neurobiology, material and surface science) to frontier technological application (nanotechnology, bioelectronics). The memristor is the fourth fundamental circuit element, whose electrical properties favor applications in signal processing, neural networks, and brain-computer interactions and it represents a new frontier for technological applications in many fields including the nanotechnologies, bioelectronics and the biosensors. Using multidisciplinary approaches, covering surface science, cell biology and electrophysiology, we successfully implemented a living bio-hybrid system constituted by cells adhering to films of poly(aniline) (PANI), a semiconductor polymer having memristive properties assembled with polyelectrolytes. Here we tested whether the PANI devices could support survivor, adhesion and differentiation of several cell lines, including the neuron-like SHSY5Y cells. Moreover, we performed electrophysiology on these cells showing that the biophysical properties are retained with differences occurring in the recorded ion currents. Taken together, the cell viability here reported is the key requirement to design and develop a reliable functional memristor-based bio-hybrid able to mimic neuronal activity and plasticity.
Directory of Open Access Journals (Sweden)
Andreza de Sousa
2014-01-01
Full Text Available The synthesis strategy of a multifunctional system of [SBA-15/Fe3O4/P(N-iPAAm] hybrids of interest for bioapplications was explored. Magnetite nanoparticles coated by mesoporous silica were prepared by an alternative chemical route using neutral surfactant and without the application of any functionalization method. Monomer adsorption followed by in situ polymerization initiated by a radical was the adopted procedure to incorporate the hydrogel into the pore channels of silica nanocomposite. Characterization of the materials was carried out by using X-ray diffraction (XRD, Fourier-transform infrared spectroscopy (FTIR, N2 adsorption, transmission electron microscopy (TEM, and Temperature programmed reduction studies (TPR. Their application as drug delivery system using atenolol as a model drug to assess the influence of the application of low frequency alternating magnetic fields on drug release was evaluated. The structural characteristics of the magnetic hybrid nanocomposite, including the effect of the swelling behavior on heating by the application of an alternating magnetic field, are presented and discussed.
Ehsani, A; Mohammad Shiri, H; Kowsari, E; Safari, R; Torabian, J; Kazemi, S
2016-09-15
An effective approach for increasing the life cycle of poly ortho aminophenol (POAP) as a p-type conductive polymers is combining conventional conductive polymers and nanomaterials to fabricate hybrid electrodes. In this paper, functionalized graphene oxide (FGO) has first been synthesized using a chemical approach. Hybrid POAP/FGO films have then been fabricated by POAP electropolymerization in the presence of FGO nanoparticles as active electrodes for electrochemical supercapacitors. Based on the atomic scale study results, it seems that H3PO4(-) oxygen atoms and terminal pyridine ring nitrogen atoms play a crucial role in the intramolecular charge and energy transfer in the FGO molecular systems. Theoretical studies, surface and electrochemical analyses have been used for characterization of POAP/FGO composite films. Different electrochemical methods including galvanostatic charge discharge experiments, cyclic voltammetry and electrochemical impedance spectroscopy have been applied to study the system performance. This work introduces new nanocomposite materials for electrochemical redox capacitors with such advantages as the ease of synthesis, high active surface area and stability in an aqueous electrolyte.
Waters, P J; Scriver, C R; Parniak, M A
2001-07-01
Phenylketonuria (PKU) is caused by mutations in the phenylalanine hydroxylase gene (PAH), while mutations in genes encoding the two enzymes (dihydropteridine reductase, DHPR, and pterin-4-alpha-carbinolamine dehydratase, PCD) required for recycling of its cofactor, tetrahydrobiopterin (BH(4)), cause other rarer disease forms of hyperphenylalaninemia. We have applied a yeast two-hybrid method, in which protein--protein interactions are measured by four reporter gene constructs, to the analysis of six PKU-associated PAH missense mutations (F39L, K42I, L48S, I65T, A104D, and R157N). By studying homomeric interactions between mutant PAH subunits, we show that this system is capable of detecting quite subtle aberrations in PAH oligomerization caused by missense mutations and that the observed results generally correlate with the severity of the mutation as determined by other expression systems. The mutant PAH subunits are also shown in this system to be able to interact with wild-type PAH subunits, pointing to an explanation for apparent dominant negative effects previously observed in obligate heterozygotes for PKU mutations. Based on our findings, the applications and limitations of two-hybrid approaches in understanding mechanisms by which PAH missense mutations exert their pathogenic effects are discussed. We have also used this technique to demonstrate homomeric interactions between wild-type DHPR subunits and between wild-type PCD subunits. These data provide a basis for functional studies on HPA-associated mutations affecting these enzymes.
Directory of Open Access Journals (Sweden)
Yan Bing
2010-01-01
Full Text Available Abstract A novel kind of organic–inorganic monomer SUASi has been achieved by modifying 5-sulfosalicylic acid (SUA with 3-aminopropyltrimethoxysilane (APS, subsequently binary and ternary Eu3+ mesoporous hybrid materials with 5-sulfosalicylic acid (SUA-functionalized SBA-15 and 1,10-phenanthroline (phen are synthesized by co-condensation of SUASi and TEOS in the presence of Eu3+ complex and Pluronic P123 as a template. Finally, luminescent hybrid mesoporous materials consisting of active rare earth ions (Eu3+—inert rare earth ions (Y3+, La3+, Gd3+ complex covalently bonded to the mesoporous materials network have been obtained via this sol–gel approach. The physical characterization and photoluminescence of all these resulting materials are studied in detail. Especially the luminescent behavior has been studied with the different ratios of Eu3+–(Y3+, La3+, Gd3+, which suggests that the existence of inert rare earth ions can enhance the luminescence intensity of Eu3+. This may be due to the intramolecular energy transfer between Y3+, La3+, Gd3+, and Eu3+ through the covalently bonded mesoporous framework.
Sakho, El hadji Mamour; Oluwafemi, Oluwatobi S.; Sreekanth, P.; Philip, Reji; Thomas, Sabu; Kalarikkal, Nandakumar
2016-08-01
Nonlinear optical (NLO) response under near infrared (800 nm) and visible (532 nm) laser excitations, of 100 fs (fs) and 5 ns (ns) pulse durations respectively, of reduced graphene oxide (RGO), non-covalent functionalized reduced graphene oxide (NF-RGO) and NF-RGO decorated with various concentration of silver nanoparticles (NF-RGO/Ag-NPs) have been investigated using the Open-aperture Z-Scan technique. For both femtosecond and nanosecond laser excitations, the studied graphene-based materials exhibit good nonlinear optical power limiting properties (OL), with NF-RGO/Ag-NPs sample prepared with 0.1 M AgNO3 showing the best nonlinear optical properties. For the ns regime, the optical limiting threshold decreased from 8.3 J/cm2 in NF-RGO to 4.3 J/cm2 in NF-RGO/Ag-NPs, while at fs regime, the nonlinear absorption coefficient (β) was found to increase with decrease in concentration of Ag-NPs in the hybrid. Two-photon absorption (2 PA) in combination with saturable absorption (SA) in femtosecond regime, and reverse saturable absorption (RSA) along with saturable absorption (SA) in the nanosecond regime, are responsible for the observed nonlinear optical absorption (NLA) behavior in these materials. These findings show that the as-synthesized NF-RGO/Ag-NPs hybrid is a relatively better material for nonlinear optical limiting applications.
Tai, Yanlong
2015-12-08
Flexible transparent conductive films (FTCFs) as the essential components of the next generation of functional circuits and devices are presently attracting more attention. Here, a new strategy has been demonstrated to fabricate thickness-controllable FTCFs through coffee ring lithography (CRL) of single-wall carbon nanotube (SWCNT)/poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT:PSS) hybrid ink. The influence of ink concentration and volume on the thickness and size of hybrid film has been investigated systematically. Results show that the final FTCFs present a high performance, including a homogeneous thickness of 60-65 nm, a sheet resistance of 1.8 kohm/sq, a visible/infrared-range transmittance (79%, PET = 90%), and a dynamic mechanical property (>1000 cycle, much better than ITO film), respectively, when SWCNT concentration is 0.2 mg/mL, ink volume is 0.4 μL, drying at room temperature. Moreover, the benefits of these kinds of FTCFs have been verified through a full transparent, flexible noncontact sensing panel (3 × 4 sensing pixels) and a flexible battery-free wireless sensor based on a humidity sensing mechanism, showing excellent human/machine interaction with high sensitivity, good stability, and fast response/recovery ability. © 2015 American Chemical Society.
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Ueno Kazuko
2009-04-01
Full Text Available Abstract Background Model checking approaches were applied to biological pathway validations around 2003. Recently, Fisher et al. have proved the importance of model checking approach by inferring new regulation of signaling crosstalk in C. elegans and confirming the regulation with biological experiments. They took a discrete and state-based approach to explore all possible states of the system underlying vulval precursor cell (VPC fate specification for desired properties. However, since both discrete and continuous features appear to be an indispensable part of biological processes, it is more appropriate to use quantitative models to capture the dynamics of biological systems. Our key motivation of this paper is to establish a quantitative methodology to model and analyze in silico models incorporating the use of model checking approach. Results A novel method of modeling and simulating biological systems with the use of model checking approach is proposed based on hybrid functional Petri net with extension (HFPNe as the framework dealing with both discrete and continuous events. Firstly, we construct a quantitative VPC fate model with 1761 components by using HFPNe. Secondly, we employ two major biological fate determination rules – Rule I and Rule II – to VPC fate model. We then conduct 10,000 simulations for each of 48 sets of different genotypes, investigate variations of cell fate patterns under each genotype, and validate the two rules by comparing three simulation targets consisting of fate patterns obtained from in silico and in vivo experiments. In particular, an evaluation was successfully done by using our VPC fate model to investigate one target derived from biological experiments involving hybrid lineage observations. However, the understandings of hybrid lineages are hard to make on a discrete model because the hybrid lineage occurs when the system comes close to certain thresholds as discussed by Sternberg and Horvitz in
Lutnaes, Ola B; Ruden, Torgeir A; Helgaker, Trygve
2004-10-01
Density functional theory, in particular, with the Becke-3-parameter-Lee-Yang-Parr (B3LYP) hybrid functional, has been shown to be a promising method for the calculation of indirect nuclear spin-spin coupling constants. However, no systematic investigation has so far been undertaken to evaluate the capability of B3LYP to calculate these coupling constants accurately, taking properly into account the vibrational contributions. In this work, vibrationally corrected indirect spin-spin coupling constants were calculated using the B3LYP functional for 10 rigid unsubstituted and substituted hydrocarbons: ethyne, ethene, allene, cyclopropene, cyclopropane, cyclobutene, pyrrole, furan, thiophene and benzene. The resulting spin-spin constants were compared with the available experimental values. The basis sets in these calculations give indirect nuclear spin-spin coupling constants of ethyne that are almost converged to the basis-set limit, making the intrinsic error of the computational method and the error in equilibrium geometry the main sources of error. On average, the B3LYP functional overestimates the indirect nuclear spin-spin coupling constants in hydrocarbons by 10%.
Energy Technology Data Exchange (ETDEWEB)
Debbichi, M., E-mail: mourad_fsm@yahoo.fr [Laboratoire de la matière condensée et nanosciences, Département de Physique, Faculté des Sciences de Monastir, 5019 Monastir (Tunisia); Sakhraoui, T. [Laboratoire de la matière condensée et nanosciences, Département de Physique, Faculté des Sciences de Monastir, 5019 Monastir (Tunisia); Debbichi, L. [Institut Carnot de Bourgogne, UMR 6303, Université de Bourgogne-CNRS, 21078 Dijon (France); Said, M. [Laboratoire de la matière condensée et nanosciences, Département de Physique, Faculté des Sciences de Monastir, 5019 Monastir (Tunisia)
2013-11-25
Highlights: •S-doped ZnO have been investigated by DFT and EPM. •Good agreement with the experimental data is obtained by HSE (α = 0.28) functional on lattice parameters and band gap energy. •Zn vacancy introduced in S doped ZnO is studied by HSE to determine its electronic and magnetic properties. -- Abstract: The structural and electronic properties of S-doped ZnO are investigated by density functional theory (DFT) and empirical pseudopotential method (EPM). Using the Heyd–Scuseria–Ernzerhof (HSE) hybrid functional with an adjusted mixing coefficient α, we obtain a good agreement on lattice parameters and band gap energy with the available experimental data. We have also investigate the Zn-vacancy effects on the electronic and magnetic properties of S-doped ZnO. Our calculations demonstrate that S impurity prefers to be close to the cation vacancy in the apical position. The magnetic analysis with the HSE functional shows a triplet state character with a total magnetic moment of 1.81 μ{sub B}, which is mainly arises from the p-orbitals of the atoms around the Zn-vacancy (15% from S, 12% from Zn and 73% from O-atoms). The substitution of S by an isovalent atom decreases the total magnetic moments of the system and weakens the local triplet state without destroying it.
Suresh Kumar, Raju; Almansour, Abdulrahman I.; Arumugam, Natarajan; Soliman, Saied M.; Ranjith Kumar, Raju; Ghabbour, Hazem A.
2016-10-01
The synthesis of highly functionalized dispiro oxindole-pyrrolo[1,2-c]thiazole-piperidone hybrid has been achieved regioselectively employing microwave-assisted three-component 1,3-dipolar cycloaddition. Structural elucidation of the compound has been accomplished using NMR spectroscopy and further confirmed by single crystal X-ray crystallographic studies. The molecular structure of the compound crystallized in monoclinic, P21/c, a = 11.6182 (2) Å, b = 12.2466 (2) Å, c = 21.7061 (3) Å, β = 103.018 (1)°, V = 3009.04 (8) Å3, Z = 4. The cycloaddition was found to proceed by normal electronic demand (NED) character with a significant high charge transfer (0.1247 eV) from the 1,3-dipole to the dipolarophile. The regiochemistry has been explained using the local reactivity descriptors obtained from the DFT calculations. The DFT optimized molecular structure agreed well with the X-ray results.