Oberhofer, H
2009-01-01
We present a plane-wave basis set implementation of charge constrained density functional molecular dynamics (CDFT-MD) for simulation of electron transfer reactions in condensed phase systems. Following earlier work of Wu et al. Phys. Rev. A 72, 024502 (2005), the density functional is minimized under the constraint that the charge difference between donor and acceptor is equal to a given value. The classical ion dynamics is propagated on the Born-Oppenheimer surface of the charge constrained state. We investigate the dependence of the constrained energy and of the energy gap on the definition of the charge, and present expressions for the constraint forces. The method is applied to the Ru2+-Ru3+ electron self-exchange reaction in aqueous solution. Sampling the vertical energy gap along CDFT-MD trajectories, and correcting for finite size effects, a reorganization free energy of 1.6 eV is obtained. This is 0.1-0.2 eV lower than a previous estimate based on a continuum model for solvation. smaller value for re...
Charge-constrained auxiliary-density-matrix methods for the Hartree–Fock exchange contribution
Three new variants of the auxiliary-density-matrix method (ADMM) of Guidon, Hutter, and VandeVondele [J. Chem. Theory Comput. 6, 2348 (2010)] are presented with the common feature that they have a simplified constraint compared with the full orthonormality requirement of the earlier ADMM1 method. All ADMM variants are tested for accuracy and performance in all-electron B3LYP calculations with several commonly used basis sets. The effect of the choice of the exchange functional for the ADMM exchange–correction term is also investigated
Cozma, M D
2016-01-01
The charged pion multiplicity ratio in intermediate energy heavy-ion collisions, a probe of the density dependence of symmetry energy above the saturation point, has been proven in a previous study to be extremely sensitive to the strength of the isovector $\\Delta$(1232) potential in nuclear matter. As there is no current knowledge, either from theory or experiment, about the magnitude of this quantity, the extraction of constraints for the slope of the symmetry energy at saturation by using exclusively the mentioned observable is hindered at present. It is shown that, by including the ratio of average $p_T$ of charged pions $\\langle p_T^{(\\pi^+)}\\rangle/\\langle p_T^{(\\pi^-)}\\rangle$ in the list of fitted observables, the noted problem can be circumvented. A realistic description of this observable requires the accounting for the interaction of pions with the dense nuclear matter environment by the incorporation of the so called S-wave and P-wave pion optical potentials. This is performed within the framework...
Charge density waves in solids
Gor'kov, LP
2012-01-01
The latest addition to this series covers a field which is commonly referred to as charge density wave dynamics.The most thoroughly investigated materials are inorganic linear chain compounds with highly anisotropic electronic properties. The volume opens with an examination of their structural properties and the essential features which allow charge density waves to develop.The behaviour of the charge density waves, where interesting phenomena are observed, is treated both from a theoretical and an experimental standpoint. The role of impurities in statics and dynamics is considered and an
Constraining the level density using fission of lead projectiles
Rodríguez-Sánchez, J. L.; Benlliure, J.; Álvarez-Pol, H.; Audouin, L.; Ayyad, Y.; Bélier, G.; Boutoux, G.; Casarejos, E.; Chatillon, A.; Cortina-Gil, D.; Gorbinet, T.; Heinz, A.; Kelić-Heil, A.; Laurent, B.; Martin, J.-F.; Paradela, C.; Pellereau, E.; Pietras, B.; Ramos, D.; Rodríguez-Tajes, C.; Rossi, D. M.; Simon, H.; Taïeb, J.; Vargas, J.; Voss, B.
2015-10-01
The nuclear level density is one of the main ingredients for the statistical description of the fission process. In this work, we propose to constrain the description of this parameter by using fission reactions induced by protons and light ions on 208Pb at high kinetic energies. The experiment was performed at GSI (Darmstadt), where the combined use of the inverse kinematics technique with an efficient detection setup allowed us to measure the atomic number of the two fission fragments in coincidence. This measurement permitted us to obtain with high precision the partial fission cross sections and the width of the charge distribution as a function of the atomic number of the fissioning system. These data and others previously measured, covering a large range in fissility, are compared to state-of-the-art calculations. The results reveal that total and partial fission cross sections cannot unambiguously constrain the level density at ground-state and saddle-point deformations and additional observables, such as the width of the charge distribution of the final fission fragments, are required.
Fundamental gap of molecular crystals via constrained density functional theory
Droghetti, Andrea; Rungger, Ivan; Das Pemmaraju, Chaitanya; Sanvito, Stefano
2016-05-01
The energy gap of a molecular crystal is one of the most important properties since it determines the crystal charge transport when the material is utilized in electronic devices. This is, however, a quantity difficult to calculate and standard theoretical approaches based on density functional theory (DFT) have proven unable to provide accurate estimates. In fact, besides the well-known band-gap problem, DFT completely fails in capturing the fundamental gap reduction occurring when molecules are packed in a crystal structures. The failure has to be associated with the inability of describing the electronic polarization and the real space localization of the charged states. Here we describe a scheme based on constrained DFT, which can improve upon the shortcomings of standard DFT. The method is applied to the benzene crystal, where we show that accurate results can be achieved for both the band gap and also the energy level alignment.
Synchronous charge-constrained electroquasistatic generator
Melcher, J. R.
1969-01-01
Electroquasistatic generator depends on electroquasistatic interactions to provide synchronous operation. The generator employs a moving insulating belt, with an ac electric potential source to establish positively and negatively charged regions on the belt. The field effect of the charges on the belt creates an ac output voltage.
Augmented Lagrangian Method for Constrained Nuclear Density Functional Theory
Staszczak, A.; Stoitsov, M.; Baran, A.; W. Nazarewicz
2010-01-01
The augmented Lagrangiam method (ALM), widely used in quantum chemistry constrained optimization problems, is applied in the context of the nuclear Density Functional Theory (DFT) in the self-consistent constrained Skyrme Hartree-Fock-Bogoliubov (CHFB) variant. The ALM allows precise calculations of multidimensional energy surfaces in the space of collective coordinates that are needed to, e.g., determine fission pathways and saddle points; it improves accuracy of computed derivatives with re...
Central depression of nuclear charge density distribution
The center-depressed nuclear charge distributions are investigated with the parametrized distribution and the relativistic mean-field theory, and their corresponding charge form factors are worked out with the phase shift analysis method. The central depression of nuclear charge distribution of 46Ar and 44S is supported by the relativistic mean-field calculation. According to the calculation, the valence protons in 46Ar and 44S prefer to occupy the 1d3/2 state rather than the 2s1/2 state, which is different from that in the less neutron-rich argon and sulfur isotopes. As a result, the central proton densities of 46Ar and 44S are highly depressed, and so are their central charge densities. The charge form factors of some argon and sulfur isotopes are presented, and the minima of the charge form factors shift upward and inward when the central nuclear charge distributions are more depressed. Besides, the effect of the central depression on the charge form factors is studied with a parametrized distribution, when the root-mean-square charge radii remain constant.
Pion transverse charge density and the edge of hadrons
Carmignotto, Marco [Catholic University of America; Horn, Tanja [Catholic University of America; Miller, Gerald A. [University of Washington
2014-08-01
We use the world data on the pion form factor for space-like kinematics and a technique used to extract the proton transverse densities, to extract the transverse pion charge density and its uncertainty due to experimental uncertainties and incomplete knowledge of the pion form factor at large values of Q2. The pion charge density at small values of b<0.1 fm is dominated by this incompleteness error while the range between 0.1-0.3 fm is relatively well constrained. A comparison of pion and proton charge densities shows that the pion is denser than the proton for values of b<0.2 fm. The pion and proton distributions seem to be the same for values of b=0.2-0.6 fm. Future data from Jlab 12 GeV and the EIC will increase the dynamic extent of the data to higher values of Q2 and thus reduce the uncertainties in the extracted pion charge density.
Charge densities and charge noise in mesoscopic conductors
M Büttiker
2002-02-01
We introduce a hierarchy of density of states to characterize the charge distribution in a mesoscopic conductor. At the bottom of this hierarchy are the partial density of states which represent the contribution to the local density of states if both the incident and the out-going scattering channel is prescribed. The partial density of states play a prominent role in measurements with a scanning tunneling microscope on multiprobe conductors in the presence of current ﬂow. The partial density of states determine the degree of dephasing generated by a weakly coupled voltage probe. In addition the partial density of states determine the frequency-dependent response of mesoscopic conductors in the presence of slowly oscillating voltages applied to the contacts of the sample. The partial density of states permit the formulation of a Friedel sum rule which can be applied locally. We introduce the off-diagonal elements of the partial density of states matrix to describe charge ﬂuctuation processes. This generalization leads to a local Wigner–Smith life-time matrix.
Constrained variation in Jastrow method at high density
A method is derived for constraining the correlation function in a Jastrow variational calculation which permits the truncation of the cluster expansion after two-body terms, and which permits exact minimization of the two-body cluster by functional variation. This method is compared with one previously proposed by Pandharipande and is found to be superior both theoretically and practically. The method is tested both on liquid 3He, by using the Lennard--Jones potential, and on the model system of neutrons treated as Boltzmann particles (''homework'' problem). Good agreement is found both with experiment and with other calculations involving the explicit evaluation of higher-order terms in the cluster expansion. The method is then applied to a more realistic model of a neutron gas up to a density of 4 neutrons per F3, and is found to give ground-state energies considerably lower than those of Pandharipande
Constraining cloud parameters using high density gas tracers in galaxies
Kazandjian, M V; Meijerink, R; Israel, F P; Coppola, C M; Rosenberg, M J F; Spaans, M
2016-01-01
Far-infrared molecular emission is an important tool used to understand the excitation mechanisms of the gas in the inter-stellar medium of star-forming galaxies. In the present work, we model the emission from rotational transitions with critical densities n >~ 10^4 cm-3. We include 4-3 ~ 30 in order to obtain significant emission from n > 10^4 cm-3 gas. Such Mach numbers are expected in star-forming galaxies, LIRGS, and ULIRGS. By fitting line ratios of HCN(1-0), HNC(1-0), and HCO+(1-0) for a sample of LIRGS and ULIRGS using mechanically heated PDRs, we constrain the Mach number of these galaxies to 29 < M < 77.
Meaningful structural descriptors from charge density.
Stalke, Dietmar
2011-08-16
This paper provides a short introduction to the basics of electron density investigations. The two predominant approaches for the modelling and various interpretations of electron density distributions are presented. Their potential translations into chemical concepts are explained. The focus of the article lies on the deduction of chemical properties from charge density studies in some selected main group compounds. The relationship between the obtained numerical data and commonly accepted simple chemical concepts unfortunately is not always straightforward, and often the chemist relies on heuristic connections rather than rigorously defined ones. This article tries to demonstrate how charge density analyses can shed light on aspects of chemical bonding and reactivity resulting from the determined bonding situation. Sometimes this helps to identify misconceptions and sets the scene for new unconventional synthetic approaches. PMID:21717511
Charge density glass from fictions to facts
Thirty years ago Fukuyama [J. Phys. Soc. Jpn. 45 (1978) 1474] predicted a transition from charge density wave (CDW) state to the charge density glass (CDG) at a finite temperature as the consequence of the competition between the uniform commensurability pinning and the random impurity pinning. We present strong evidence that the CDG phase indeed exists as a generic feature of density wave systems. However, it arises from the competition of the random impurity pinning and the electrostatic intra-CDW interaction which tends to establish a uniform phase at low temperature. The glass transition occurs at the temperature at which the free carriers cannot efficiently screen the phase distortions. The characteristic length scale of the disorder, i.e. the size of the phase coherent domains, governs the glass properties
A Charge-Conjugation-Invariance Constrained Pomeron-Quark Coupling
Liu, Lon-chang
2005-01-01
The commonly used $\\gamma_{\\mu}} Pomeron-quark coupling changes its sign under charge conjugation, in contradiction to the property of Pomeron. I show that the Pomeron-quark coupling is tensorial and is invariant under the charge conjugation.
The number density of a charged relic
We investigate scenarios in which a charged, long-lived scalar particle decouples from the primordial plasma in the Early Universe. We compute the number density at time of freeze-out considering both the cases of abelian and non-abelian interactions and including the effect of Sommerfeld enhancement at low initial velocity. We also discuss as extreme case the maximal cross section that fulfils the unitarity bound. We then compare these number densities to the exotic nuclei searches for stable relics and to the BBN bounds on unstable relics and draw conclusions for the cases of a stau or stop NLSP in supersymmetric models with a gravitino or axino LSP. (orig.)
Density functional theory of charged colloidal systems
The phase behavior of charged colloidal systems has been studied recently by the density functional theory formalism (DFT) [R. van Roij, M. Dijkstra, and J. P. Hansen, Phys. Rev. E >59, 2010 (1999)]. A key feature of this approach is the appearance of a density and temperature-dependent effective Hamiltonian between the charged colloids. Under certain approximations, the effective Hamiltonian is made up only of a sum of position-independent one-body or volume terms and two-body colloid-separation dependent terms. In the limit of low colloidal densities, the DFT results do not reduce to the familiar Debye-Huckel limiting law nor do the results agree with previous work based on an identical approach but were developed using traditional statistical-mechanical methods [B. Beresford-Smith, D. Y. C. Chan, and D. J. Mitchell J. Colloid Interface Sci. >105, 216 (1985)]. This paper provides a reconciliation of these differences and comments on the significance of the one-body volume terms in the effective Hamiltonian of a system of charged colloids in determining thermodynamics and phase behavior
Charge density path in cold fusion reactions
Cold fusion reactions are very frequently employed to produce compound nuclei with a relatively low excitation energy, which is extremely important for a successful synthesis method, particularly in the region of superheavy nuclei. Usually the charge densities of the projectile, target, and compound nucleus are different. We present a method allowing to take into consideration this difference continuously during the fusion process. Applications are given both in the intermediate mass and the superheavy region. Different cold fusion paths are studied with respect to the change of the charge density within the overlapping region. A transition formula from separated fusion partners up to the compound nucleus is obtained as depending on the geometrical changes. Macroscopic-microscopic approach is used to compute the total deformation energy. Shell corrections are obtained with Strutinsky method, having the new deformed two-center single particle energy levels as an input. Yukawa-plus-exponential model is employed to compute the macroscopic part. Spheroidal deformations are taken into account. By changing the absolute value of semiaxes as well as their ratio, the charge densities of the partners are modified during fusion. As a result of minimization against different paths of the semiaxes ratios from projectile and target values to synthesized nucleus, charge density variation can lower the cold fusion deformation energy. This kind of influence is especially active in the last part of the fusion process, when the projectile is already at least half embedded in the target. For cold fusion of light and intermediate nuclei, the energy variation in the last part of the deformation path reaches 4 MeV for 102 Ru and 3.7 MeV for 152 Dy synthesis. For a possible superheavy production the influence of charge density changes are quantitatively more important. The energy difference in the cold fusion channel barrier of 292 116 reaches about 8 MeV in the last part of the
Turban, David H P; O'Regan, David D; Hine, Nicholas D M
2016-01-01
Singlet fission (SF) is a multi-exciton generation process that could be harnessed to improve the efficiency of photovoltaic devices. Experimentally, systems derived from the pentacene molecule have been shown to exhibit ultrafast SF with high yields. Charge-transfer (CT) configurations are likely to play an important role as intermediates in the SF process in these systems. In molecular crystals, electrostatic screening effects and band formation can be significant in lowering the energy of CT states, enhancing their potential to effectively participate in SF. In order to simulate these, it desirable to adopt a computational approach which is acceptably accurate, relatively inexpensive, which and scales well to larger systems, thus enabling the study of screening effects. We propose a novel, electrostatically-corrected constrained Density Functional Theory (cDFT) approach as a low-cost solution to the calculation of CT energies in molecular crystals such as pentacene. Here we consider an implementation in th...
Turban, David H. P.; Teobaldi, Gilberto; O'Regan, David D.; Hine, Nicholas D. M.
2016-04-01
Singlet fission (SF) is a multiexciton generation process that could be harnessed to improve the efficiency of photovoltaic devices. Experimentally, systems derived from the pentacene molecule have been shown to exhibit ultrafast SF with high yields. Charge-transfer (CT) configurations are likely to play an important role as intermediates in the SF process in these systems. In molecular crystals, electrostatic screening effects and band formation can be significant in lowering the energy of CT states, enhancing their potential to effectively participate in SF. In order to simulate these, it desirable to adopt a computational approach which is acceptably accurate, relatively inexpensive, and which scales well to larger systems, thus enabling the study of screening effects. We propose an electrostatically corrected constrained density functional theory (cDFT) approach as a low-cost solution to the calculation of CT energies in molecular crystals such as pentacene. Here we consider an implementation in the context of the onetep linear-scaling DFT code, but our electrostatic correction method is in principle applicable in combination with any constrained DFT implementation, also outside the linear-scaling framework. Our newly developed method allows us to estimate CT energies in the infinite crystal limit, and with these to validate the accuracy of the cluster approximation.
Liu, Zhaoxi; Wu, Qiuwei; Oren, Shmuel S.;
2016-01-01
This paper presents a distribution locational marginal pricing (DLMP) method through chance constrained mixed-integer programming designed to alleviate the possible congestion in the future distribution network with high penetration of electric vehicles (EVs). In order to represent the stochastic...... characteristics of the EV driving patterns, a chance constrained optimization of the EV charging is proposed and formulated through mixed-integer programming (MIP). With the chance constraints in the optimization formulations, it guarantees that the failure probability of the EV charging plan fulfilling...... constrained MIP can successfully alleviate the congestion in the distribution network due to the EV charging while keeping the failure probability of EV charging not meeting driving needs below the predefined confidence....
A Duality Between Unidirectional Charge Density Wave Order and Superconductivity
Lee, Dung-Hai
2001-01-01
This paper shows the existence of a duality between an unidirectional charge density wave order and a superconducting order. This duality predicts the existence of charge density wave near a superconducting vortex, and the existence of superconductivity near a charge density wave dislocation.
Device for measuring charge density distribution in charged particle beams
A device to measure charge density distribution in charged particle beams has been described. The device contains a set of hollow interinsulated current-receiving electrodes, recording system, and cooling system. The invention is aimed at the increase of admissible capacity of the beams measured at the expense of cooling efficiency increase. The aim is achieved by the fact, that in the device a dynamic evaporating-condensational cooling of electrodes is realized by means of cooling agent supply in perpendicular to their planes through the tubes introduced inside special cups. Spreading in radial direction over electrode surface the cooling agent gradually and intensively washes the side surface of the cup, after that, it enters the cooling cavity in the form of vapour-liquid mixture. In the cavity the cooling agent, supplied using dispensina and receiving collectors in which vapoUr is condensed, circulates. In the device suggested the surface of electrode cooling is decreased significantly at the expense of side surface of the cups which receives the electrode heat
Fragment approach to constrained density functional theory calculations using Daubechies wavelets
Ratcliff, Laura E., E-mail: lratcliff@anl.gov [Argonne Leadership Computing Facility, Argonne National Laboratory, Lemont, Illinois 60439 (United States); Université de Grenoble Alpes, CEA, INAC-SP2M, L-Sim, F-38000 Grenoble (France); Genovese, Luigi; Mohr, Stephan; Deutsch, Thierry [Université de Grenoble Alpes, CEA, INAC-SP2M, L-Sim, F-38000 Grenoble (France)
2015-06-21
In a recent paper, we presented a linear scaling Kohn-Sham density functional theory (DFT) code based on Daubechies wavelets, where a minimal set of localized support functions are optimized in situ and therefore adapted to the chemical properties of the molecular system. Thanks to the systematically controllable accuracy of the underlying basis set, this approach is able to provide an optimal contracted basis for a given system: accuracies for ground state energies and atomic forces are of the same quality as an uncontracted, cubic scaling approach. This basis set offers, by construction, a natural subset where the density matrix of the system can be projected. In this paper, we demonstrate the flexibility of this minimal basis formalism in providing a basis set that can be reused as-is, i.e., without reoptimization, for charge-constrained DFT calculations within a fragment approach. Support functions, represented in the underlying wavelet grid, of the template fragments are roto-translated with high numerical precision to the required positions and used as projectors for the charge weight function. We demonstrate the interest of this approach to express highly precise and efficient calculations for preparing diabatic states and for the computational setup of systems in complex environments.
Fragment approach to constrained density functional theory calculations using Daubechies wavelets
In a recent paper, we presented a linear scaling Kohn-Sham density functional theory (DFT) code based on Daubechies wavelets, where a minimal set of localized support functions are optimized in situ and therefore adapted to the chemical properties of the molecular system. Thanks to the systematically controllable accuracy of the underlying basis set, this approach is able to provide an optimal contracted basis for a given system: accuracies for ground state energies and atomic forces are of the same quality as an uncontracted, cubic scaling approach. This basis set offers, by construction, a natural subset where the density matrix of the system can be projected. In this paper, we demonstrate the flexibility of this minimal basis formalism in providing a basis set that can be reused as-is, i.e., without reoptimization, for charge-constrained DFT calculations within a fragment approach. Support functions, represented in the underlying wavelet grid, of the template fragments are roto-translated with high numerical precision to the required positions and used as projectors for the charge weight function. We demonstrate the interest of this approach to express highly precise and efficient calculations for preparing diabatic states and for the computational setup of systems in complex environments
Nuclear Energy Density Functionals Constrained by Low-Energy QCD
Vretenar, Dario
2008-01-01
A microscopic framework of nuclear energy density functionals is reviewed, which establishes a direct relation between low-energy QCD and nuclear structure, synthesizing effective field theory methods and principles of density functional theory. Guided by two closely related features of QCD in the low-energy limit: a) in-medium changes of vacuum condensates, and b) spontaneous breaking of chiral symmetry; a relativistic energy density functional is developed and applied in studies of ground-s...
Nuclear spectroscopy on charge density wave systems
This book is the first coherent presentation of investigations of charge density wave (CDW) systems by nuclear spectroscopic techniques. It is addressed to the graduate students and elder scientist who are interested in modern aspects of solid state physics and want to acquire a broader knowledge of nuclear spectroscopy techniques applied to CDW systems. Chapter 1 gives a short introduction to CDW's in general and to the question what can be learned about CDW's by nuclear spectroscopy techniques. Chapter 2 gives a Landau theory description of CDW formation in chain-like tetrachalcogenides. Chapter 3 treats experimental results on layered transition metal compounds. A short introduction to nuclear magnetic resonance (NMR), nuclear quadrupole resonance (NQR), time differential perturbed angular correlation (TDPAC), and the Moessbauer effect (ME) is included in this chapter because all three techniques have been extensively applied to Ta-dichalcogenides which are prominent members of this family of materials. Chapter 4 and 5 treat in great detail CDW dynamics and transport in chain-like like transition metal chalcogenides and molybdenum bronzes, respectively. Chapter 6 treats the one-dimensional inorganic complex salt K-2Pt(CN)4Br0.3.2H2O (KCP) studied by NMR on a variety of nuclei. Chapter 7 demonstrates the tremendous advances of high resolution NMR in yielding spin density maps of organic radical salts and is intended to stimulate the application of this powerful technique more directly to CDW phenomena
Constrained Density Functional Calculations of alpha and delta Pu
Eriksson, Olle
2002-03-01
The electronic structure of α and δ Pu are described using a modified density functional theory that incorporates localization effects of the 5f shell. It is argued that a Russel-Saunders coupled state involving a 5f^4 multiplet, together with one itinerant 5f electron explains most of the observed ground state properties of δ Pu (equilibrium volume, elastic constants, near degeneracy with the alpha phase). This 5f electrons in the α phase are argued to form itinerant states, that are well described in density functional theory. The two distinctly different electronic ground states give rise to different excitation spectra and a comparison with experimental data is made.
Doping-induced Charge-Density-Wave
Nomura, Atsushi; Yamaya, Kazuhiko; Takayanagi, Shigeru; Ichimura, Koichi; Matsuura, Toru; Tanda, Satoshi; Hokkaido University Team
Doping is a useful method for searching new characters in solids, as we can see in the discoveries of impurity semiconductors and high-temperature superconductors. If a Charge-Density-Wave (CDW) is induced in materials which do not exhibit a CDW, new CDW properties might be brought there. TaSe3 exhibits no CDW transition but a superconductivity transition at about 2 K while it has a quasi-one-dimensional chain structure as well as typical CDW conductors, NbSe3, TaS3, and NbS3. Therefore, TaSe3 is one of the suitable materials for the induction of a CDW by doping, and we tried to induce a CDW in TaSe3 by doping Cu. Cu concentration was determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The high Cu concentration was consistent with the high value of residual resistance (R (4 . 5 K) / (R (280 K) - R (4 . 5 K))). Single-crystal X-ray diffraction pattern (XRD) showed an expansion of the c-axis in Cu-doped TaSe3. The temperature dependence of the resistivity showed the anomaly at 80-100 K in Cu-doped TaSe3, which was never observed in pure TaSe3. These results suggest that the Cu-doping induces a CDW. We will discuss the relation between the resistivity anomaly and superconductivity.
Stretched hydrogen molecule from a constrained-search density-functional perspective
Valone, Steven M [Los Alamos National Laboratory; Levy, Mel [DIKE UNIV.
2009-01-01
Constrained-search density functional theory gives valuable insights into the fundamentals of density functional theory. It provides exact results and bounds on the ground- and excited-state density functionals. An important advantage of the theory is that it gives guidance in the construction of functionals. Here they engage constrained search theory to explore issues associated with the functional behavior of 'stretched bonds' in molecular hydrogen. A constrained search is performed with familiar valence bond wavefunctions ordinarily used to describe molecular hydrogen. The effective, one-electron hamiltonian is computed and compared to the corresponding uncorrelated, Hartree-Fock effective hamiltonian. Analysis of the functional suggests the need to construct different functionals for the same density and to allow a competition among these functions. As a result the correlation energy functional is composed explicitly of energy gaps from the different functionals.
Constraining the cosmic radiation density due to lepton number
The cosmic energy density in the form of radiation before and during Big Bang Nucleosynthesis is typically parameterized in terms of the effective number of neutrinos Neff, and it is a key parameters in cosmological models slightly more general than the successful minimal ΛCDM scenario. This quantity, in case of no extra degrees of freedom, depends upon the chemical potential and the temperature characterizing the three active neutrino distributions, as well as by their possible non-thermal features. We summarize here the results of a recent analysis to determine the BBN bound on Neff from primordial neutrino–antineutrino asymmetries, with a careful treatment of the dynamics of neutrino oscillations, and considering quite a wide range for the total lepton number in the neutrino sector, ην=ηνe+ηνμ+ηντ and the initial electron neutrino asymmetry ηνein. Comparing these results with the forthcoming measurement of Neff by the Planck satellite will give insight on the nature of the radiation content of the universe
Constraining the cosmic radiation density due to lepton number
Mangano, Gianpiero [Istituto Nazionale di Fisica Nucleare - Sezione di Napoli Complesso Universitario di Monte S. Angelo, I-80126 Napoli (Italy); Miele, Gennaro [Istituto Nazionale di Fisica Nucleare - Sezione di Napoli Complesso Universitario di Monte S. Angelo, I-80126 Napoli (Italy); Dipartimento di Scienze Fisiche, Università di Napoli Federico II Complesso Universitario di Monte S. Angelo, I-80126 Napoli (Italy); Pastor, Sergio [Instituto de Física Corpuscular (CSIC-Universitat de València), Ed. Institutos de Investigación, Apdo. correos 22085, E-46071 Valencia (Spain); Pisanti, Ofelia [Istituto Nazionale di Fisica Nucleare - Sezione di Napoli Complesso Universitario di Monte S. Angelo, I-80126 Napoli (Italy); Dipartimento di Scienze Fisiche, Università di Napoli Federico II Complesso Universitario di Monte S. Angelo, I-80126 Napoli (Italy); Sarikas, Srdjan [Dipartimento di Scienze Fisiche, Università di Napoli Federico II Complesso Universitario di Monte S. Angelo, I-80126 Napoli (Italy); Max-Planck-Institut für Physik (Werner-Heisenberg-Institut) Föhringer Ring 6, 80802 München (Germany)
2013-04-15
The cosmic energy density in the form of radiation before and during Big Bang Nucleosynthesis is typically parameterized in terms of the effective number of neutrinos N{sub eff}, and it is a key parameters in cosmological models slightly more general than the successful minimal ΛCDM scenario. This quantity, in case of no extra degrees of freedom, depends upon the chemical potential and the temperature characterizing the three active neutrino distributions, as well as by their possible non-thermal features. We summarize here the results of a recent analysis to determine the BBN bound on N{sub eff} from primordial neutrino–antineutrino asymmetries, with a careful treatment of the dynamics of neutrino oscillations, and considering quite a wide range for the total lepton number in the neutrino sector, η{sub ν}=η{sub ν{sub e}}+η{sub ν{sub μ}}+η{sub ν{sub τ}} and the initial electron neutrino asymmetry η{sub ν{sub e}{sup in}}. Comparing these results with the forthcoming measurement of N{sub eff} by the Planck satellite will give insight on the nature of the radiation content of the universe.
On the charge density and asymptotic tail of a monopole
Harland, Derek
2015-01-01
We propose a new definition for the abelian magnetic charge density of a non-abelian monopole, based on zero-modes of an associated Dirac operator. Unlike the standard definition of the charge density, this density is smooth in the core of the monopole. We show that this charge density induces a magnetic field whose expansion in powers of 1/r agrees with that of the conventional asymptotic magnetic field to all orders. We also show that the asymptotic field can be easily calculated from the spectral curve. Explicit examples are given for known monopole solutions.
Local covariant density functional constrained by the relativistic Hartree-Fock theory
Liang, H Z; Ring, P; Roca-Maza, X; Zhao, P W; 10.1063/1.4764245
2012-01-01
The recent progress in the localized covariant density functional constrained by the relativistic Hartree-Fock theory is briefly presented by taking the Gamow-Teller resonance in 90Zr as an example. It is shown that the constraints introduced by the Fock terms into the particle-hole residual interactions are straight forward and robust.
Possibilities of increasing coal charge density by adding fuel oil
M. Fröhlichová
2010-01-01
Full Text Available The requirement of all coke-making facilities is to achieve the highest possible production of high quality coke from a chamber. It can be achieved by filling the effective capacity of the chamber with the highest possible amount of coal. One of the possibilities of meeting this requirement is to increase the charge density in the coke chamber. In case of a coke battery operating on bulk coal there are many methods to increase the charge density including the use of wetting agents in the charge. This article presents the results of the laboratory experiments aiming at the increase of the charge density using fuel oil as a wetting agent. The experiments were carried out by means of the Pitin’s device using 3 coal charges with various granularity composition and moisture content of 7, 8, 9 and 10 %.
A charge-density study of crystalline beryllium
The X-ray structure factors for crystalline beryllium measured by Brown [Phil. Mag. (1972), 26, 1377] have been analyzed with multipole deformation functions for charge-density information. Single exponential radial functions were used for the valence charge density. A valence monopole plus the three harmonics, P35(cos theta) sin 3phi, P6(cos theta) and P37(cos theta) sin 3phi, provide a least-squares fit to the data with Rsub(w)=0.0081. The superposition of these density functions describes a bonding charge density between Be atoms along the c axis through the tetrahedral vacancy. The results reported here are in qualitative agreement with a recent pseudo-potential calculation of metallic beryllium. The final residuals in the analysis are largest at high sin theta/lambda values. This suggests that core charge deformation is present and/or anharmonic motion of the nuclei is appreciable. (Auth.)
About Charge Density Wave for Electromagnetic Field-Drive
Guay, B T
1999-01-01
To generate a propulsive force without propellant and external couplings, it has been shown that two confined macroscopic and time-varying charge density waves well separated in space are needed. Here, some physical conditions will be proposed to support and maintain these particular collective modes of charge distributions.
Do plasma proteins distinguish between liposomes of varying charge density?
Capriotti, Anna Laura
2012-03-01
Cationic liposomes (CLs) are one of the most employed nonviral nanovector systems in gene therapy. However, their transfection efficiency is strongly affected by interactions with plasma components, that lead to the formation of a "protein corona" onto CL surface. The interactions between nanoparticles entering the body and biomolecules have an essential role for their biodistribution. Because the knowledge of proteins adsorbed onto vector surface could be useful in the screening of new, more efficient and more biocompatible liposomal formulations, the behavior of three CLs with different membrane charge densities was investigated. The proteins of the three coronas were identified by nano-liquid chromatography-tandem mass spectrometry, and quantified with label-free spectral counting strategy. Fibrinogen displayed higher association with CLs with high membrane charge density, while apolipoproteins and C4b-binding protein with CLs with low membrane charge density. These results are discussed in terms of the different lipid compositions of CLs and may have a deep biological impact for in vivo applications. Surface charge of nanoparticles is emerging as a relevant factor determining the corona composition after interaction with plasma proteins. Remarkably, it is also shown that the charge of the protein corona formed around CLs is strongly related to their membrane charge density. © 2012 Elsevier B.V.
Density-functional theory cannot be constrained to completely overcome self-interaction error
Moynihan, Glenn; O'Regan, David D
2016-01-01
In approximate density functional theory (DFT), the self-interaction error is a pervasive electron delocalization associated with underestimated insulating gaps. It exhibits a predominantly quadratic energy-density curve that is amenable to correction using computationally efficient, constraint-resembling methods such as DFT + Hubbard U (DFT+U). Constrained DFT (cDFT) exactly enforces conditions on DFT by means of self-consistently optimized Lagrange multipliers, and its use to automate DFT+U type corrections is a compelling possibility. We show that constraints beyond linear order are incompatible with cDFT. For DFT+U, we overcome this by separating its Hubbard U parameters into linear and quadratic terms. For a one-electron system, the resulting generalized DFT+U method can recover the exact subspace occupancy and free-energy, but neither the exact total-energy nor the exact ionization potential, for reasonable parameters. Approximate functionals thus cannot be systematically corrected by constraining their...
Nuclear charge radii: Density functional theory meets Bayesian neural networks
Utama, Raditya; Piekarewicz, Jorge
2016-01-01
The distribution of electric charge in atomic nuclei is fundamental to our understanding of the complex nuclear dynamics and a quintessential observable to validate nuclear structure models. We explore a novel approach that combines sophisticated models of nuclear structure with Bayesian neural networks (BNN) to generate predictions for the charge radii of thousands of nuclei throughout the nuclear chart. A class of relativistic energy density functionals is used to provide robust predictions for nuclear charge radii. In turn, these predictions are refined through Bayesian learning for a neural network that is trained using residuals between theoretical predictions and the experimental data. Although predictions obtained with density functional theory provide a fairly good description of experiment, our results show significant improvement (better than 40%) after BNN refinement. Moreover, these improved results for nuclear charge radii are supplemented with theoretical error bars. We have successfully demonst...
The effect of polymer charge density and charge distribution on the formation of multilayers
Voigt, U; Tauer, K; Hahn, M; Jäger, W; Klitzing, K V
2003-01-01
Polyelectrolyte multilayers which are built up by alternating adsorption of polyanions and polycations from aqueous solutions at a solid interface are investigated by reflectometry and ellipsometry. Below a degree of charge of about 70% the adsorption stops after a certain number of dipping cycles and no multilayer formation occurs. This indicates an electrostatically driven adsorption process. Below a charge density of 70% an adsorption can take place if the charged segments are combined as a block of the polymer.
K B Joshi; Nishant N Patel
2008-02-01
Charge density calculations and electronic band structures for GaAl1- = 1.0, 0.5 and 0.0 are presented in this work. The calculations are performed using the empirical pseudopotential method. The charge density is computed for a number of planes, i.e. = 0:0, 0.125 and 0.25 0 by generating the potential through a number of potential parameters available in the literature. The virtual crystal approximation was applied for the semiconducting alloy. The characteristics of the band structure and charge density are observed to be affected by the potential parameters. Calculated band gaps and the nature of gaps are in good agreement with the experimental data reported. The ionicity is also reasonably in good agreement with other scales proposed in the literature; however the formulation needs to be improved. The present work also demands indirect experimental band gap for the alloy.
Electron charge densities at conduction-band edges of semiconductors
We demonstrate that both the empirical pseudopotential method (EPM) and the linear combination of atomiclike orbitals (LCAO) approach are capable of producing consistent electronic charge distributions in a compound semiconductor. Since the EPM approach is known to produce total valence electron charge densities which compare well with experimental x-ray data (e.g., Si), this work serves as a further test for the LCAO method. In particular, the EPM scheme, which uses an extended plane-wave basis, and the LCAO scheme, which employs a localized Gaussian basis, are used, with the same empirical potential as input, to analyze both the total valence electron charge density and the charge density of the first conduction band at the GAMMA, L, and X k points of the Brillouin zone. These charge densities are decomposed into their s-, p-, and d-orbital contributions, and this information is used to interpret the differences in the topologies of the conduction bands at GAMMA, L, and X. Such differences are crucial for a comprehensive understanding of interstitial impurities and the response of specific band states to perturbations in compound semiconductors
Gravity dual of spin and charge density waves
Jokela, Niko; Järvinen, Matti(Crete Center for Theoretical Physics, Department of Physics, University of Crete, 71003, Heraklion, Greece); Lippert, Matthew
2014-01-01
At high enough charge density, the homogeneous state of the D3-D7’ model is unstable to fluctuations at nonzero momentum. We investigate the end point of this instability, finding a spatially modulated ground state, which is a charge and spin density wave. We analyze the phase structure of the model as a function of chemical potential and magnetic field and find the phase transition from the homogeneous state to be first order, with a second-order critical point at zero magnetic field.
Determination of charge densities in ReO3
The charge densities in ReO3 were investigated by the x-ray structural analysis. The anisotropic charge distributions were found around a Re atom, which is attributable to the π bond formed by Re 5d (tsub(2g) and O 2p electrons. The calculated difference electron density map by the DV-Xα cluster method supports qualitatively the present observation. The measured thermal vibrations of oxygen atoms were highly anisotropic. The M-mode oxygen displacements will be readily enhanced by the existence of high pressures. (author)
Branched–linear polyion complexes at variable charge densities
Structural behavior of complexes formed by a charged and branched copolymer and an oppositely charged and linear polyion was examined by Monte Carlo simulations employing a coarse-grained bead–spring model. The fractional bead charge and the branching density were systematically varied; the former between 0e and 1e and the latter such that both the comb-polymer and the bottle-brush limits were included. The number of beads of the main chain of the branched copolymer and of the linear polyion was always kept constant and equal, and a single side-chain length was used. Our analysis involved characterization of the complex as well as investigation of size, shape, and flexibility of the charged moieties. An interplay between Coulomb interaction and side-chain repulsion governed the structure of the polyion complex. At strong Coulomb interaction, the complexes underwent a gradual transition from a globular structure at low branching density to an extended one at high branching density. As the electrostatic coupling was decreased, the transition was smoothened and shifted to lower branching density, and, eventually, a behavior similar to that found for neutral branched polymer was observed. Structural analogies and dissimilarities with uncharged branched polymers in poor solutions are discussed. (paper)
Pressure induced Superconductivity in the Charge Density Wave Compound Tritelluride
Hamlin, J.J.; Zocco, D.A.; Sayles, T.A.; Maple, M.B.; /UC, Davis; Chu, J.-H.; Fisher, I.R.; /Stanford U., Geballe Lab.
2010-02-15
A series of high-pressure electrical resistivity measurements on single crystals of TbTe{sub 3} reveal a complex phase diagram involving the interplay of superconducting, antiferromagnetic and charge density wave order. The onset of superconductivity reaches a maximum of almost 4 K (onset) near {approx} 12.4 GPa.
Charge density wave dynamics from ultrafast XUV ARPES
Frassetto F.
2013-03-01
Full Text Available Ultrafast angle–resolved XUV photoemission reveals the time- and momentum-dependent electronic structure of 1T–TaS2, a hybrid Mott and charge-density-wave insulator. Both electronic orderings melt well before the lattice responds, suggesting that electronic correlations play a role not just in the Mott localization but in the CDW ordering as well.
Gate effect in charge-density wave nanowires
Slot, E.; Holst, M.A.; Van der Zant, H.S.J.
2005-01-01
We have investigated transport characteristics of charge-density wave nanowires with a few hundred parallel chains. At temperatures below50K, these samples show power-law behavior in temperature and voltage, characteristic for one-dimensional transport. In this regime, gate dependent transport has b
Beyond Poisson-Boltzmann: Numerical Sampling of Charge Density Fluctuations.
Poitevin, Frédéric; Delarue, Marc; Orland, Henri
2016-07-01
We present a method aimed at sampling charge density fluctuations in Coulomb systems. The derivation follows from a functional integral representation of the partition function in terms of charge density fluctuations. Starting from the mean-field solution given by the Poisson-Boltzmann equation, an original approach is proposed to numerically sample fluctuations around it, through the propagation of a Langevin-like stochastic partial differential equation (SPDE). The diffusion tensor of the SPDE can be chosen so as to avoid the numerical complexity linked to long-range Coulomb interactions, effectively rendering the theory completely local. A finite-volume implementation of the SPDE is described, and the approach is illustrated with preliminary results on the study of a system made of two like-charge ions immersed in a bath of counterions. PMID:27075231
Constrained Kalman Filtering Via Density Function Truncation for Turbofan Engine Health Estimation
Simon, Dan; Simon, Donald L.
2006-01-01
Kalman filters are often used to estimate the state variables of a dynamic system. However, in the application of Kalman filters some known signal information is often either ignored or dealt with heuristically. For instance, state variable constraints (which may be based on physical considerations) are often neglected because they do not fit easily into the structure of the Kalman filter. This paper develops an analytic method of incorporating state variable inequality constraints in the Kalman filter. The resultant filter truncates the PDF (probability density function) of the Kalman filter estimate at the known constraints and then computes the constrained filter estimate as the mean of the truncated PDF. The incorporation of state variable constraints increases the computational effort of the filter but significantly improves its estimation accuracy. The improvement is demonstrated via simulation results obtained from a turbofan engine model. The turbofan engine model contains 3 state variables, 11 measurements, and 10 component health parameters. It is also shown that the truncated Kalman filter may be a more accurate way of incorporating inequality constraints than other constrained filters (e.g., the projection approach to constrained filtering).
Battery peak charge voltage monitor for dual air density satellite
Shull, T. A.
1975-01-01
A battery peak charge voltage monitor was developed for use on the dual air density satellite (DADS). This device retains a reading of the maximum voltage reached by the spacecraft battery during periods of charging, and makes it available during periods of data transmission. The monitor is connected across the battery and operates solely from the battery; it is powered continuously with quiescent input current of only 3 milliamperes. Standard integrated circuits and a thin-film resistor network are utilized. The monitor occupies approximately 40 square centimeters of a printed-circuit board within a larger electronic package.
Jensen, Mogens Høgh; Lomdahl, P. S.
1982-01-01
lower and higher charge than ±2e / 3. The effect of discreteness is taken into account and gives rise to chaotic deformed solitons as the interchain coupling increases. The model may be applied to tetrathiafulvalene tetracyanoquinodimethane (TTF-TCNQ) under 19-kbar pressure.......We have studied the effect of interchain interaction on thermally excited solitons in a charge-density wave for a Peierls system of commensurability 3. In such a system solitons with charges ±2e / 3 are expected. It is shown that the interchain coupling in some cases will generate solitons with...
Geometric interpretation of density displacements and charge sensitivities
Roman F Nalewajski
2005-09-01
The ``geometric” interpretation of the electronic density displacements in the Hilbert space is given and the associated projection-operator partitioning of the hardness and softness operators (kernels) is developed. The eigenvectors |á 〉 = \\{| 〉 \\} of the hardness operator define the complete (identity) projector $\\hat{P}$ = | 〉 〈 = 1 for general density displacements, including the charge-transfer (CT) component, while the eigenvectors | i 〉 = { | 〉} of the linear response operator determine the polarizational -projector, $\\hat{P}$ = | 〉 〈 |. Their difference thus defines the complementary CT-projector: $\\hat{P}$ = 1 - $\\hat{P}$. The complete vector space for density displacements can be also spanned by supplementing the -modes with the homogeneous CT-mode. These subspaces separate the integral (normalization) and local aspects of density shifts in molecular systems.
Fast electronic resistance switching involving hidden charge density wave states
Vaskivskyi, I.; Mihailovic, I. A.; Brazovskii, S.; Gospodaric, J.; Mertelj, T.; Svetin, D.; Sutar, P.; Mihailovic, D.
2016-05-01
The functionality of computer memory elements is currently based on multi-stability, driven either by locally manipulating the density of electrons in transistors or by switching magnetic or ferroelectric order. Another possibility is switching between metallic and insulating phases by the motion of ions, but their speed is limited by slow nucleation and inhomogeneous percolative growth. Here we demonstrate fast resistance switching in a charge density wave system caused by pulsed current injection. As a charge pulse travels through the material, it converts a commensurately ordered polaronic Mott insulating state in 1T-TaS2 to a metastable electronic state with textured domain walls, accompanied with a conversion of polarons to band states, and concurrent rapid switching from an insulator to a metal. The large resistance change, high switching speed (30 ps) and ultralow energy per bit opens the way to new concepts in non-volatile memory devices manipulating all-electronic states.
Fast electronic resistance switching involving hidden charge density wave states.
Vaskivskyi, I; Mihailovic, I A; Brazovskii, S; Gospodaric, J; Mertelj, T; Svetin, D; Sutar, P; Mihailovic, D
2016-01-01
The functionality of computer memory elements is currently based on multi-stability, driven either by locally manipulating the density of electrons in transistors or by switching magnetic or ferroelectric order. Another possibility is switching between metallic and insulating phases by the motion of ions, but their speed is limited by slow nucleation and inhomogeneous percolative growth. Here we demonstrate fast resistance switching in a charge density wave system caused by pulsed current injection. As a charge pulse travels through the material, it converts a commensurately ordered polaronic Mott insulating state in 1T-TaS2 to a metastable electronic state with textured domain walls, accompanied with a conversion of polarons to band states, and concurrent rapid switching from an insulator to a metal. The large resistance change, high switching speed (30 ps) and ultralow energy per bit opens the way to new concepts in non-volatile memory devices manipulating all-electronic states. PMID:27181483
Scattered surface charge density: A tool for surface characterization
Naydenov, Borislav
2011-11-28
We demonstrate the use of nonlocal scanning tunneling spectroscopic measurements to characterize the local structure of adspecies in their states where they are significantly less perturbed by the probe, which is accomplished by mapping the amplitude and phase of the scattered surface charge density. As an example, we study single-H-atom adsorption on the n-type Si(100)-(4 × 2) surface, and demonstrate the existence of two different configurations that are distinguishable using the nonlocal approach and successfully corroborated by density functional theory. © 2011 American Physical Society.
Pion transverse charge density from timelike form factor data
Gerald Miller, Mark Strikman, Christian Weiss
2011-01-01
The transverse charge density in the pion can be represented as a dispersion integral of the imaginary part of the pion form factor in the timelike region. This formulation incorporates information from e+e- annihilation experiments and allows one to reconstruct the transverse density much more accurately than from the spacelike pion form factor data alone. We calculate the transverse density using an empirical parametrization of the timelike pion form factor and estimate that it is determined to an accuracy of ~10% at a distance b ~ 0.1 fm, and significantly better at larger distances. The density is found to be close to that obtained from a zero-width rho meson pole over a wide range and shows a pronounced rise at small distances. The resulting two-dimensional image of the fast-moving pion can be interpreted in terms of its partonic structure in QCD. We argue that the singular behavior of the charge density at the center requires a substantial presence of pointlike configurations in the pion's partonic wave function, which can be probed in other high-momentum transfer processes.
Surface Phason-Polaritons in Charge Density Wave Films
Wonneberger, W.; Lamche, R.
1997-01-01
The coupled non-radiative excitations of the electromagnetic field and phasons in films with a quasi one-dimensional charge density wave (CDW) are evaluated for P--polarization and CDW conducting axis inside the film. The prominent features are two surface phason-polariton branches extending from the CDW pinning frequency to the frequency of the longitudinal optical phason. These surface phason-polariton states are confined to a finite band of longitudinal wave numbers. Besides surface polari...
Odd parity charge density-wave scattering in cuprates
Seibold, G; Grilli, M.; Lorenzana, J.
2009-01-01
We investigate a model where superconducting electrons are coupled to a frequency dependent charge-density wave (CDW) order parameter Delta(w). Our approach can reconcile the simultaneous existence of low energy Bogoljubov quasiparticles and high energy electronic order as observed in scanning tunneling microscopy (STM) experiments. The theory accounts for the contrast reversal in the STM spectra between positive and negative bias observed above the pairing gap. An intrinsic relation between ...
X-ray spectrum of a pinned charge density wave
Rosso, Alberto; Giamarchi, Thierry
2004-01-01
We calculate the x-ray diffraction spectrum produced by a pinned charge density wave (CDW). The signature of the presence of a CDW consists of two satellite peaks, asymmetric as a consequence of disorder. The shape and the intensity of these peaks are determined in the case of a collective weak pinning using the variational method. We predict divergent asymmetric peaks, revealing the presence of a Bragg glass phase. We deal also with the long range Coulomb interactions, concluding that both p...
Non-linear conductivity of charge-density-wave systems
Werner, C. R.; Eckern, U.
1997-01-01
We consider the problem of sliding motion of a charge-density-wave subject to static disorder within an elastic medium model. Starting with a field-theoretical formulation, which allows exact disorder averaging, we propose a self-consistent approximation scheme to obtain results beyond the standard large-velocity expansion. Explicit calculations are carried out in three spatial dimensions. For the conductivity, we find a strong-coupling regime at electrical fields just above the pinning thres...
Distribution of charge and matter in nuclei: Charge density difference of 206Pb and 205Tl
We contrast two calculations of the charge density difference of 206Pb and 205Tl. In the simplest model this difference in charge density is due to the occupation of an additional 3s/sub 1/2/ orbital in 206Pb. A standard mean-field calculation of the charge difference does not yield a satisfactory result. One may modify this result by assigning the 3s/sub 1/2/ orbital an occupation probability of seventy percent, with a corresponding increase to thirty percent of the occupation probability of a 2d/sub 3/2/ orbital. However, this modification of the mean-field analysis, while solving one problem, is seen to create a new problem in the fit to the data. In this work we present an alternative analysis: We maintain unit occupation probability for the 3s/sub 1/2/ orbital but use the medium-modified proton electromagnetic form factor we have calculated previously. Our model is able to give a better fit to the data without the introduction of free parameters into the analysis. Medium-modified form factors have recently been shown to be effective in explaining the charge distribution of 208Pb and their application to the interpretation of the 206Pb-205Tl charge density difference yields a result which is consistent with the experimental data and superior to that obtained in the adjusted mean-field analysis described above
Zhou, Shan-Gui
2016-06-01
The intrinsic nuclear shapes deviating from a sphere not only manifest themselves in nuclear collective states but also play important roles in determining nuclear potential energy surfaces (PES’s) and fission barriers. In order to describe microscopically and self-consistently nuclear shapes and PES’s with as many shape degrees of freedom as possible included, we developed multidimensionally constrained covariant density functional theories (MDC-CDFTs). In MDC-CDFTs, the axial symmetry and the reflection symmetry are both broken and all deformations characterized by {β }λ μ with even μ are considered. We have used the MDC-CDFTs to study PES’s and fission barriers of actinides, the non-axial octupole Y 32 correlations in N = 150 isotones and shapes of hypernuclei. In this Review we will give briefly the formalism of MDC-CDFTs and present the applications to normal nuclei.
Zhou, Shan-Gui
2016-01-01
The intrinsic nuclear shapes deviating from a sphere not only manifest themselves in nuclear collective states but also play important roles in determining nuclear potential energy surfaces (PES's) and fission barriers. In order to describe microscopically and self-consistently nuclear shapes and PES's with as many shape degrees of freedom as possible included, we developed multidimensionally-constrained covariant density functional theories (MDC-CDFTs). In MDC-CDFTs, the axial symmetry and the reflection symmetry are both broken and all deformations characterized by $\\beta_{\\lambda\\mu}$ with even $\\mu$ are considered. We have used the MDC-CDFTs to study PES's and fission barriers of actinides, the non-axial octupole $Y_{32}$ correlations in $N = 150$ isotones and shapes of hypernuclei. In this Review we will give briefly the formalism of MDC-CDFTs and present the applications to normal nuclei.
Constraining decaying dark energy density models with the CMB temperature-redshift relation
Jetzer, Philippe
2012-01-01
We discuss the thermodynamic and dynamical properties of a variable dark energy model with density scaling as $\\rho_x \\propto (1+z)^{m}$, z being the redshift. These models lead to the creation/disruption of matter and radiation, which affect the cosmic evolution of both matter and radiation components in the Universe. In particular, we have studied the temperature-redshift relation of radiation, which has been constrained using a recent collection of cosmic microwave background (CMB) temperature measurements up to $z \\sim 3$. We find that, within the uncertainties, the model is indistinguishable from a cosmological constant which does not exchange any particles with other components. Future observations, in particular measurements of CMB temperature at large redshift, will allow to give firmer bounds on the effective equation of state parameter $w_{eff}$ for such types of dark energy models.
Constraining the gravitational wave energy density of the Universe using Earth's ring
Coughlin, Michael
2014-01-01
The search for gravitational waves is one of today's major scientific endeavors. A gravitational wave can interact with matter by exciting vibrations of elastic bodies. Earth itself is a large elastic body whose so-called normal-mode oscillations ring up when a gravitational wave passes. Therefore, precise measurement of vibration amplitudes can be used to search for the elusive gravitational-wave signals. Earth's free oscillations that can be observed after high-magnitude earthquakes have been studied extensively with gravimeters and low-frequency seismometers over many decades leading to invaluable insight into Earth's structure. Making use of our detailed understanding of Earth's normal modes, numerical models are employed for the first time to accurately calculate Earth's gravitational-wave response, and thereby turn a network of sensors that so far has served to improve our understanding of Earth, into an astrophysical observatory exploring our Universe. In this article, we constrain the energy density o...
Charge Order Induced in an Orbital Density-Wave State
Singh, Dheeraj Kumar; Takimoto, Tetsuya
2016-04-01
Motivated by recent angle resolved photoemission measurements [D. V. Evtushinsky et al., Phys. Rev. Lett. 105, 147201 (2010)] and evidence of the density-wave state for the charge and orbital ordering [J. García et al., Phys. Rev. Lett. 109, 107202 (2012)] in La0.5Sr1.5MnO4, the issue of charge and orbital ordering in a two-orbital tight-binding model for layered manganite near half doping is revisited. We find that the charge order with the ordering wavevector 2{Q} = (π ,π ) is induced by the orbital order of d-/d+-type having B1g representation with a different ordering wavevector Q, where the orbital order as the primary order results from the strong Fermi-surface nesting. It is shown that the induced charge order parameter develops according to TCO - T by decreasing the temperature below the orbital ordering temperature TCO, in addition to the usual mean-field behavior of the orbital order parameter. Moreover, the same orbital order is found to stabilize the CE-type spin arrangement observed experimentally below TCE < TCO.
Modeling charged defects inside density functional theory band gaps
Density functional theory (DFT) has emerged as an important tool to probe microscopic behavior in materials. The fundamental band gap defines the energy scale for charge transition energy levels of point defects in ionic and covalent materials. The eigenvalue gap between occupied and unoccupied states in conventional DFT, the Kohn–Sham gap, is often half or less of the experimental band gap, seemingly precluding quantitative studies of charged defects. Applying explicit and rigorous control of charge boundary conditions in supercells, we find that calculations of defect energy levels derived from total energy differences give accurate predictions of charge transition energy levels in Si and GaAs, unhampered by a band gap problem. The GaAs system provides a good theoretical laboratory for investigating band gap effects in defect level calculations: depending on the functional and pseudopotential, the Kohn–Sham gap can be as large as 1.1 eV or as small as 0.1 eV. We find that the effective defect band gap, the computed range in defect levels, is mostly insensitive to the Kohn–Sham gap, demonstrating it is often possible to use conventional DFT for quantitative studies of defect chemistry governing interesting materials behavior in semiconductors and oxides despite a band gap problem
Charge density waves in strongly correlated electron systems
Chen, Chih-Wei; Choe, Jesse; Morosan, E.
2016-08-01
Strong electron correlations are at the heart of many physical phenomena of current interest to the condensed matter community. Here we present a survey of the mechanisms underlying such correlations in charge density wave (CDW) systems, including the current theoretical understanding and experimental evidence for CDW transitions. The focus is on emergent phenomena that result as CDWs interact with other charge or spin states, such as magnetism and superconductivity. In addition to reviewing the CDW mechanisms in 1D, 2D, and 3D systems, we pay particular attention to the prevalence of this state in two particular classes of compounds, the high temperature superconductors (cuprates) and the layered transition metal dichalcogenides. The possibilities for quantum criticality resulting from the competition between magnetic fluctuations and electronic instabilities (CDW, unconventional superconductivity) are also discussed.
Charge-density waves physics revealed by photoconduction
Zaitsev-Zotov, S.V., E-mail: serzz@cplire.ru [Kotel' nikov Institute of Radio-engineering and Electronics of the RAS, 125009 Moscow (Russian Federation); Moscow Institute of Physics and Technology, 141700 Dolgoprudny (Russian Federation); Nasretdinova, V.F.; Minakova, V.E. [Kotel' nikov Institute of Radio-engineering and Electronics of the RAS, 125009 Moscow (Russian Federation)
2015-03-01
The results of photoconduction study of the Peierls conductors are reviewed. The studied materials are quasi-one-dimensional conductors with the charge-density wave: K{sub 0.3}MoO{sub 3}, both monoclinic and orthorhombic TaS{sub 3} and also a semiconducting phase of NbS{sub 3} (phase I). Experimental methods, relaxation times, effects of illumination on linear and nonlinear charge transport, the electric-field effect on photoconduction and results of the spectral studies are described. We demonstrate, in particular, that a simple model of modulated energy gap slightly smoothed by fluctuations fits the available spectral data fairly well. The level of the fluctuations is surprisingly small and does not exceed a few percent of the optical energy gap value.
Charge density waves in strongly correlated electron systems.
Chen, Chih-Wei; Choe, Jesse; Morosan, E
2016-08-01
Strong electron correlations are at the heart of many physical phenomena of current interest to the condensed matter community. Here we present a survey of the mechanisms underlying such correlations in charge density wave (CDW) systems, including the current theoretical understanding and experimental evidence for CDW transitions. The focus is on emergent phenomena that result as CDWs interact with other charge or spin states, such as magnetism and superconductivity. In addition to reviewing the CDW mechanisms in 1D, 2D, and 3D systems, we pay particular attention to the prevalence of this state in two particular classes of compounds, the high temperature superconductors (cuprates) and the layered transition metal dichalcogenides. The possibilities for quantum criticality resulting from the competition between magnetic fluctuations and electronic instabilities (CDW, unconventional superconductivity) are also discussed. PMID:27376547
Measuring charge density of electron beam single nanosecond pulses
A description is presented of a probe design and electrometric repeater circuit and technique for measuring the charge (current) density of electron beam single pulses by integrating current at a reference capacitor with a subsequent registering of voltage across the capacitor. The probe consists of a band-type signal electrodes and two oval cross-section sleeves: external and internal with larger and smaller rectangular openings, respectively. The external sleeve has antidynatron grid located over the hole. The design employs integer nickel sleever - the cores of electron tube cathodes. The signal electrode is made of nickel band 0.15 mm thick. The probe elements are insulated from each other along the whole length with a layer of teflon band (30 μm), with rectangular openings cut in compliance with the sleeve openings. The measurement range is from 0.4x10-9 to 1x10-7 C/cm2. The rated accuracy of measurements is no worse than +-5% for the beam energy of 0.2 to 3 KeV. The ultimate parameters the charge density -6 C/cm2 and direct current density 3 mA/cm2 - are specified by the breakdown voltage (200 V) of the input capacitor and probe insulation
Leherte, Laurence; Vercauteren, Daniel P
2011-10-01
To generate reduced point charge models of proteins, we developed an original approach to hierarchically locate extrema in charge density distribution functions built from the Poisson equation applied to smoothed molecular electrostatic potential (MEP) functions. A charge fitting program was used to assign charge values to the so-obtained reduced representations. In continuation to a previous work, the Amber99 force field was selected. To easily generate reduced point charge models for protein structures, a library of amino acid templates was designed. Applications to four small peptides, a set of 53 protein structures, and four KcsA ion channel models, are presented. Electrostatic potential and solvation free energy values generated by the reduced models are compared with the corresponding values obtained using the original set of atomic charges. Results are in closer agreement with the original all-atom electrostatic properties than those obtained with a previous reduced model that was directly built from the smoothed MEP functions [Leherte and Vercauteren in J Chem Theory Comput 5:3279-3298, 2009]. PMID:21915750
Mantle density beneath the Siberian craton based on free board constrains
Cherepanova, Yulia; Artemieva, Irina
2014-05-01
We present the mantle density model of the Archean-Proterozoic Siberian Craton (SC). The density model is constrained by free-board (buoyancy) modeling (Lachenbruch and Morgan, 1990). The approach assumes isostatic compensation of the region, and is justified by the near-zero free-air gravity for most of the region, except for the flanking orogenic belts with high topography. Despite a relatively uniform topography of the SC (ca. 400 m for most of the region and reaching 700 m in the shields), the craton has a strongly heterogeneous crustal structure with large regional variations in Moho and average crustal Vp (Cherepanova et al., 2013) which reflects its complex tectonic evolution. Formed by amalgamation of several Archean terranes, the craton has been significantly affected by Proterozoic collisional and extensional events, the late- Proterozoic rifting at its margins, the Devonian rifting of the Vilyui rift, several pulses of kimberlite magmatism, and the Permo-Triassic trap basalt magmatism. The strong lateral and vertical heterogeneity of the lithospheric mantle has been documented so far in the studied of the mantle xenoliths from kimberlite pipes and in a limited number of geophysical studies. Here we extend geophysical analysis of mantle compositional heterogeneity by evaluating mantle density structure and interpreting its regional variations in terms of mantle mg#. We link regional large-amplitude variations in mantle depletion to the tectonic evolution of the craton and compare these results with geophysical models and petrologic data. We speculate on the origin of compositional heterogeneity of the lithospheric mantle, which is in overall agreement with results of a joint analysis of seismic and thermal data (Artemieva, 2009) and mantle xenolith studies which provide information on metasomatic enrichment of the depleted lithospheric mantle by the tectonic events. The results indicate the heterogeneous structure of mantle density, with the average
Constraining turbulence and conduction in the hot ICM through density perturbations
Gaspari, M
2013-01-01
Using 3D high-resolution hydrodynamic simulations, we study the interplay of varying conduction and turbulence in the hot intracluster medium, tracking both electrons and ions. We exploit the power spectrum of the relative gas density perturbations, to precisely constrain conduction and turbulence. The normalization of the characteristic amplitude of perturbations determines the strength of turbulence, since it is linearly related to the Mach number: A_max = 0.25 M. The slope of the spectrum defines the level of conduction. In a non-conductive medium, subsonic stirring motions generate a density `cascade' which is nearly Kolmogorov. Instead, increasing conduction (with magnetic suppression f = 0.001 -> 1) progressively steepens the spectrum towards the sharp Burgers regime. The turbulent Prandtl number defines the dynamic similarity of the flow. The threshold P_t 0.1), P_t ~ 100 occurs on spatial scales larger than the injection scale. This regime would be also manifest in the SB_x or residual images, in whi...
Charge carrier density in Li-intercalated graphene
Kaloni, Thaneshwor P.
2012-05-01
The electronic structures of bulk C 6Li, Li-intercalated free-standing bilayer graphene, and Li-intercalated bilayer and trilayer graphene on SiC(0 0 0 1) are studied using density functional theory. Our estimate of Young\\'s modulus suggests that Li-intercalation increases the intrinsic stiffness. For decreasing Li-C interaction, the Dirac point shifts to the Fermi level and the associated band splitting vanishes. For Li-intercalated bilayer graphene on SiC(0 0 0 1) the splitting at the Dirac point is tiny. It is also very small at the two Dirac points of Li-intercalated trilayer graphene on SiC(0 0 0 1). For all the systems under study, a large enhancement of the charge carrier density is achieved by Li intercalation. © 2012 Elsevier B.V. All rights reserved.
Size dependence of the surface charge density in EDL-MF
Tourinho, F. A.; Campos, A. F. C.; Aquino, R.; Lara, M. C. F. L.; Depeyrot, J.
2002-11-01
We determine the surface charge density of electric double layered magnetic fluids based on manganese ferrite nanoparticles of two different sizes using simultaneous potentiometric-conductimetric titrations. The saturation superficial density of charge is reduced for smaller particles.
Size dependence of the surface charge density in EDL-MF
We determine the surface charge density of electric double layered magnetic fluids based on manganese ferrite nanoparticles of two different sizes using simultaneous potentiometric-conductimetric titrations. The saturation superficial density of charge is reduced for smaller particles
The gravitational effect on induced charge density for an obliquely rotating neutron star
The effect om the induced charge density of the gravitational field of a rotating neutron star with its magnetic axis inclined with respect to the rotational axis is investigated. While gravitation increases the charge density the obliquity reduces it
The gravitational effect on induced charge density for an obliquely rotating neutron star
De Paolis, F. [Delaware Univ., Newark (United States). Bartol Research Inst.; Istituto Nazionale di Fisica Nucleare, Lecce (Italy); Qadir, A. [Quaid-i-Azam Univ., Islamabad (Pakistan). Dept. of Mathematics; Tarman, I.H. [King Fahd University of Petroleum and Minerals, Dharan (Saudi Arabia). Dept. of Mathematical Sciences
1999-11-01
The effect om the induced charge density of the gravitational field of a rotating neutron star with its magnetic axis inclined with respect to the rotational axis is investigated. While gravitation increases the charge density the obliquity reduces it.
Shells of charge: a density functional theory for charged hard spheres.
Roth, Roland; Gillespie, Dirk
2016-06-22
A functional for the electrostatic excess free-energy for charged, hard sphere fluids is proposed. The functional is derived from two complementary, but equivalent, interpretations of the mean spherical approximation (MSA). The first combines fundamental measure theory (FMT) from hard-core interactions with the idea that MSA can be interpreted in terms of the interaction spherical shells of charge. This formulation gives the free-energy density as a function of weighted densities. When all the ions have the same size, the functional adopts an FMT-like form. The second in effect 'functionalizes' the derivation of MSA; that is, it generalizes the MSA as a functional-based version of MSA (fMSA). This formulation defines the free-energy density as a function of a position-dependent MSA screening parameter and the weighted densities of the FMT approach. This FMT/fMSA functional is shown to give accurate density profiles, as compared to Monte Carlo simulations, under a wide range of ion concentrations, size asymmetries, and valences. PMID:27116385
The Charge Density and Electrostatic Potential of Three Dinitramide Salts
Martin, Anthony
The aim of this dissertation was to obtain information about the redistribution of electrons due to effects such as chemical bonding using X-ray diffraction. There is a great deal of current interest in the production of new energetic materials. A new class of the salts based on the dinitramide anion, N(NO _2)_sp{2}{-}, DN has attracted some interest. Three dinitramide salts (ammonium, monoprotonated and diprotonated biguanidinium) have been selected for charge density analyses on the basis of the observed variation of the dinitramide anion in the room temperature structures and the potential applications of these compounds. However, while a good deal of work has gone into the methodology of charge density studies, relatively little has been done to improve the presentation of the results. As a result the quality of presentation has remained essentially unchanged for twenty years. While this may sound like a triviality, it is visualization of data that produces information. Existing programs have been modified to produce output suitable for improved visualization, in particular using color and 3D computer graphics. From a chemist's viewpoint there were two aims for this project. The first was to see if the difference in the geometries of the dinitramide ion is reflected in the size and shape of the bonding electron density using experimental methods. The second aim was to obtain the electrostatic potential of the materials based on the experimentally determined electron density distribution in order to obtain some insight into the reactivity of the dinitramide ion. The different geometries produce observable differences in the deformation density. The electrostatic potential derived from the experimental electron density also shows variations with respect to the geometry and environment. These potentials have different minima and are also different from potentials produced from gas phase semi-empirical and ab-initio calculations. Whether the reactivity can be
Spin and charge density waves in the Lieb lattice
Gouveia, J. D.; Dias, R. G.
2016-05-01
We study the mean-field phase diagram of the two-dimensional (2D) Hubbard model in the Lieb lattice allowing for spin and charge density waves. Previous studies of this diagram have shown that the mean-field magnetization surprisingly deviates from the value predicted by Lieb's theorem [1] as the on-site repulsive Coulomb interaction (U) becomes smaller [2]. Here, we show that in order for Lieb's theorem to be satisfied, a more complex mean-field approach should be followed in the case of bipartite lattices or other lattices whose unit cells contain more than two types of atoms. In the case of the Lieb lattice, we show that, by allowing the system to modulate the magnetization and charge density between sublattices, the difference in the absolute values of the magnetization of the sublattices, mLieb, at half-filling, saturates at the exact value 1/2 for any value of U, as predicted by Lieb. Additionally, Lieb's relation, mLieb = 1 / 2, is verified approximately for large U, in the n ∈ [ 2 / 3 , 4 / 3 ] range. This range includes not only the ferromagnetic region of the phase diagram of the Lieb lattice (see Ref. [2]), but also the adjacent spiral regions. In fact, in this lattice, below or at half-filling, mLieb is simply the filling of the quasi-flat bands in the mean-field energy dispersion both for large and small U.
Constraining the Bulk Density of 10m-Class Near-Earth Asteroid 2012 LA
Mommert, Michael; Hora, Joseph; Farnocchia, Davide; Trilling, David; Chesley, Steve; Harris, Alan; Mueller, Migo; Smith, Howard
2016-08-01
The physical properties of near-Earth asteroids (NEAs) provide important hints on their origin, as well as their past physical and orbital evolution. Recent observations seem to indicate that small asteroids are different than expected: instead of being monolithic bodies, some of them instead resemble loose conglomerates of smaller rocks, so called 'rubble piles'. This is surprising, since self-gravitation is practically absent in these bodies. Hence, bulk density measurements of small asteroids, from which their internal structure can be estimated, provide unique constraints on asteroid physical models, as well as models for asteroid evolution. We propose Spitzer Space Telescope observations of 10 m-sized NEA 2012 LA, which will allow us to constrain the diameter, albedo, bulk density, macroporosity, and mass of this object. We require 30 hrs of Spitzer time to detect our target with a minimum SNR of 3 in CH2. In order to interpret our observational results, we will use the same analysis technique that we used in our successful observations and analyses of tiny asteroids 2011 MD and 2009 BD. Our science goal, which is the derivation of the target's bulk density and its internal structure, can only be met with Spitzer. Our observations will produce only the third comprehensive physical characterization of an asteroid in the 10m size range (all of which have been carried out by our team, using Spitzer). Knowledge of the physical properties of small NEAs, some of which pose an impact threat to the Earth, is of importance for understanding their evolution and estimating the potential of destruction in case of an impact, as well as for potential manned missions to NEAs for either research or potential commercial uses.
Carroll, Raymond J.
2011-03-01
In many applications we can expect that, or are interested to know if, a density function or a regression curve satisfies some specific shape constraints. For example, when the explanatory variable, X, represents the value taken by a treatment or dosage, the conditional mean of the response, Y , is often anticipated to be a monotone function of X. Indeed, if this regression mean is not monotone (in the appropriate direction) then the medical or commercial value of the treatment is likely to be significantly curtailed, at least for values of X that lie beyond the point at which monotonicity fails. In the case of a density, common shape constraints include log-concavity and unimodality. If we can correctly guess the shape of a curve, then nonparametric estimators can be improved by taking this information into account. Addressing such problems requires a method for testing the hypothesis that the curve of interest satisfies a shape constraint, and, if the conclusion of the test is positive, a technique for estimating the curve subject to the constraint. Nonparametric methodology for solving these problems already exists, but only in cases where the covariates are observed precisely. However in many problems, data can only be observed with measurement errors, and the methods employed in the error-free case typically do not carry over to this error context. In this paper we develop a novel approach to hypothesis testing and function estimation under shape constraints, which is valid in the context of measurement errors. Our method is based on tilting an estimator of the density or the regression mean until it satisfies the shape constraint, and we take as our test statistic the distance through which it is tilted. Bootstrap methods are used to calibrate the test. The constrained curve estimators that we develop are also based on tilting, and in that context our work has points of contact with methodology in the error-free case.
Boson ground state fields in electroweak theory with non-zero charge densities
Syska, J.
2002-01-01
The "non-linear" self-consistent theory of classical fields in the electroweak model is proposed. Homogeneous boson ground state solutions in the GSW model at the presence of a non-zero extended fermionic charge densities are reviewed and fully reinterpreted to make the theory with non-zero charge densities fruitful. Consequences of charge density fluctuations are proposed.
Matveev, Oleg; Shvaika, Andrij; Devereaux, Thomas; Freericks, James
The charge-density-wave phase of the Falicov-Kimball model displays a number of anomalous behavior including the appearance of subgap density of states as the temperature increases. These subgap states should have a significant impact on transport properties, particularly the nonlinear response of the system to a large dc electric field. Using the Kadanoff-Baym-Keldysh formalism, we employ nonequilibrium dynamical mean-field theory to exactly solve for this nonlinear response. We examine both the current and the order parameter of the conduction electrons as the ordered system is driven by a dc electric field. Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, Lviv, Ukraine.
Electromagnetic form factors and charge densities from hadrons to nuclei
A simple exact covariant model in which a scalar particle Ψ is modeled as a bound state of two different particles is used to elucidate relativistic aspects of electromagnetic form factors F(Q2). The model form factor is computed using an exact covariant calculation of the lowest order triangle diagram. The light-front technique of integrating over the minus component of the virtual momentum gives the same result and is the same as the one obtained originally by Gunion et al. [Phys. Rev. D 8, 287 (1973)] by using time-ordered perturbation theory in the infinite-momentum frame. The meaning of the transverse density ρ(b) is explained by providing a general derivation, using three spatial coordinates, of its relationship with the form factor. This allows us to identify a mean-square transverse size 2>=∫d2b b2ρ(b)=-4(dF/dQ2)(Q2=0). The quantity 2> is a true measure of hadronic size because of its direct relationship with the transverse density. We show that the rest-frame charge distribution is generally not observable by studying the explicit failure to uphold current conservation. Neutral systems of two charged constituents are shown to obey the conventional lore that the heavier one is generally closer to the transverse origin than the lighter one. It is argued that the negative central charge density of the neutron arises, in pion-cloud models, from pions of high longitudinal momentum that reside at the center. The nonrelativistic limit is defined precisely, and the ratio of the binding energy B to the mass M of the lightest constituent is shown to govern the influence of relativistic effects. It is shown that the exact relativistic formula for F(Q2) is the same as the familiar one of the three-dimensional Fourier transform of a square of a wave function for very small values of B/M, but this only occurs for values of B/M less than about 0.001. For masses that mimic the quark-diquark model of the nucleon we find that there are substantial relativistic
Mapping of charge density of ion beams produced by laser
Krása, Josef; Parys, P.; Velyhan, Andriy; Margarone, Daniele; Krouský, Eduard; Ullschmied, Jiří
Vol. 38F. Mulhouse : European Physical Society, 2014 - (Ratynskaia, S.; Mantica, P.; Benuzzi-Mounaix, A.; Dilecce, G.; Bingham, R.; Hirsch, M.; Kemnitz, B.; Klinger, T.), "P2.094-1"-"P2.094-4" ISBN 2-914771-90-8. - (Europhysics Conference Abstracts (ECA)). [EPS Conference on Plasma Physics/41./. Berlin (DE), 23.06.2014-27.06.2014] R&D Projects: GA MŠk EE2.3.20.0279; GA ČR GAP205/12/0454 Grant ostatní: LaserZdroj (OP VK 3)(XE) CZ.1.07/2.3.00/20.0279 Institutional support: RVO:68378271 ; RVO:61389021 Keywords : laser ion sources * map of ion charge density * ion expansion * modeling Subject RIV: BL - Plasma and Gas Discharge Physics http://ocs.ciemat.es/EPS2014PAP/pdf/P2.094.pdf
Thermodynamics of superconductors with charge-density waves
Gabovich, A M; Szymczak, H; Voitenko, A I
2003-01-01
Equations for the temperature-(T-) dependent superconducting (DELTA(T)) and dielectric (SIGMA(T)) order parameters are solved self-consistently in the partial dielectric gapping model of Bilbro and McMillan for superconductors with charge-density waves (CDWs). It is shown that for the close enough structural phase transition temperature, T sub s , and superconducting one, T sub c , with T sub s > T sub c , SIGMA below T sub c may become smaller than DELTA. The electronic heat capacity C(T) is calculated. It is shown that the discontinuity DELTA C at T = T sub c is always smaller than the Bardeen-Cooper-Schrieffer value. The effect is detectable over a wide range of the model parameters. Experimental implications for CDW superconductors, such as A15 compounds, high-T sub c cuprates, and MgB sub 2 , are suggested and discussed.
Umar, A. S.; Oberacker, V. E.
2008-01-01
We present a fully microscopic study of the $^{16}$O+$^{208}$Pb fusion using the density-constrained time-dependent Hartree-Fock theory. The calculated fusion cross-sections are in good agreement with the experimental data for the entire energy range indicating that the incorporation of dynamical effects is crucial in describing heavy-ion fusion.
Connection between charge-density-wave order and charge transport in the cuprate superconductors
Tabis, W.; Li, Y; Tacon, M. Le; Braicovich, L.; Kreyssig, A.; Minola, M.; Dellea, G.; Weschke, E.; Veit, M. J.; Ramazanoglu, M.; Goldman, A. I.; T. Schmitt; Ghiringhelli, G.; Barišić, N.; Chan, M. K.
2014-01-01
Charge-density-wave (CDW) correlations within the quintessential CuO$_2$ planes have been argued to either cause [1] or compete with [2] the superconductivity in the cuprates, and they might furthermore drive the Fermi-surface reconstruction in high magnetic fields implied by quantum oscillation (QO) experiments for YBa$_2$Cu$_3$O$_{6+{\\delta}}$ (YBCO) [3] and HgBa$_2$CuO$_{4+{\\delta}}$ (Hg1201) [4]. Consequently, the observation of bulk CDW order in YBCO was a significant development [5,6,7]...
Constraining the cosmic radiation density due to lepton number with Big Bang Nucleosynthesis
Mangano, Gianpiero; Miele, Gennaro; Pisanti, Ofelia; Sarikas, Srdjan [Istituto Nazionale di Fisica Nucleare – Sezione di Napoli, Complesso Universitario di Monte S. Angelo, I-80126 Napoli (Italy); Pastor, Sergio, E-mail: mangano@na.infn.it, E-mail: miele@na.infn.it, E-mail: pastor@ific.uv.es, E-mail: pisanti@na.infn.it, E-mail: sarikas@na.infn.it [Instituto de Física Corpuscular (CSIC-Universitat de València), Ed. Institutos de Investigación, Apdo. correos 22085, E-46071 Valencia (Spain)
2011-03-01
The cosmic energy density in the form of radiation before and during Big Bang Nucleosynthesis (BBN) is typically parameterized in terms of the effective number of neutrinos N{sub eff}. This quantity, in case of no extra degrees of freedom, depends upon the chemical potential and the temperature characterizing the three active neutrino distributions, as well as by their possible non-thermal features. In the present analysis we determine the upper bounds that BBN places on N{sub eff} from primordial neutrino-antineutrino asymmetries, with a careful treatment of the dynamics of neutrino oscillations. We consider quite a wide range for the total lepton number in the neutrino sector, η{sub ν} = η{sub ν{sub e}}+η{sub ν{sub μ}}+η{sub ν{sub τ}} and the initial electron neutrino asymmetry η{sub ν{sub e}{sup in}}, solving the corresponding kinetic equations which rule the dynamics of neutrino (antineutrino) distributions in phase space due to collisions, pair processes and flavor oscillations. New bounds on both the total lepton number in the neutrino sector and the ν{sub e}−ν-bar {sub e} asymmetry at the onset of BBN are obtained fully exploiting the time evolution of neutrino distributions, as well as the most recent determinations of primordial {sup 2}H/H density ratio and {sup 4}He mass fraction. Note that taking the baryon fraction as measured by WMAP, the {sup 2}H/H abundance plays a relevant role in constraining the allowed regions in the η{sub ν}−η{sub ν{sub e}{sup in}} plane. These bounds fix the maximum contribution of neutrinos with primordial asymmetries to N{sub eff} as a function of the mixing parameter θ{sub 13}, and point out the upper bound N{sub eff}∼<3.4. Comparing these results with the forthcoming measurement of N{sub eff} by the Planck satellite will likely provide insight on the nature of the radiation content of the universe.
Plane density of induced vacuum charge in a supercritical Coulomb potential
Khalilov, V R
2016-01-01
An expression for the density of a planar induced vacuum charge is obtained in a strong Coulomb potential in coordinate space. Treatment is based on a self-adjoint extension approach for constructing of the Green's function of a charged fermion in this potential. Induced vacuum charge density is calculated and analyzed at the subcritical and supercritical Coulomb potentials for massless and massive fermions. The behavior of the obtained vacuum charge density is investigated at long and short distances from the Coulomb center. The induced vacuum charge has a screening sign. Screening of a Coulomb impurity in graphene is briefly discussed. We calculate the real vacuum polarization charge density that acquires the quantum electrodynamics vacuum in the supercritical Coulomb potential due to the so-called real vacuum polarization. It is shown that the vacuum charge densities essentially differ in massive and massless cases. We expect that our results can, as a matter of principle, be tested in graphene with a supe...
Validity of the evidence for a central depression in the charge density of 3He
The derivation of proton and neutron charge densities from experimentally obtained form factors is considered. The meson exchange current contribution to the 3He charge form factor for three models of neutron and proton charge form factors is calculated and it is shown that it is not valid to use the short range behavior of nucleon charge density to deduce information on the structure of 3He
Oscar H. Lücke
2010-01-01
Full Text Available The map of complete Bouguer anomaly of Costa Rica shows an elongated NW-SE trending gravity low in the central region. This gravity low coincides with the geographical region known as the Cordillera Volcánica Central. It is built by geologic and morpho-tectonic units which consist of Quaternary volcanic edifices. For quantitative interpretation of the sources of the anomaly and the characterization of fluid pathways and reservoirs of arc magmatism, a constrained 3D density model of the upper crust was designed by means of forward modeling. The density model is constrained by simplified surface geology, previously published seismic tomography and P-wave velocity models, which stem from wide-angle refraction seismic, as well as results from methods of direct interpretation of the gravity field obtained for this work. The model takes into account the effects and influence of subduction-related Neogene through Quaternary arc magmatism on the upper crust.
Charge-density matching in organic-inorganic uranyl compounds
Single crystals of [C10H26N2][(UO2)(SeO4)2(H2O)](H2SeO4)0.85(H2O)2 (1), [C10H26N2][(UO2)(SeO4)2] (H2SeO4)0.50(H2O) (2), and [C8H20N]2[(UO2)(SeO4)2(H2O)] (H2O) (3) were prepared by evaporation from aqueous solution of uranyl nitrate, selenic acid and the respective amines. The structures of the compounds have been solved by direct methods and structural models have been obtained. The structures of the compounds 1, 2, and 3 contain U and Se atoms in pentagonal bipyramidal and tetrahedral coordinations, respectively. The UO7 and SeO4 polyhedra polymerize by sharing common O atoms to form chains (compound 1) or sheets (compounds 2 and 3). In the structure of 1, the layers consisting of hydrogen-bonded [UO2(SeO4)2(H2O)]2- chains are separated by mixed organic-inorganic layers comprising from [NH3(CH2)10NH3]2+ molecules, H2O molecules, and disordered electroneutral (H2SeO4) groups. The structure of 2 has a similar architecture but a purely inorganic layer is represented by a fully connected [UO2(SeO4)2]2- sheet. The structure of 3 does not contain disordered (H2SeO4) groups but is based upon alternating [UO2(SeO4)2(H2O)]2- sheets and 1.5-nm-thick organic blocks consisting of positively charged protonated octylamine molecules, [NH3(CH2)7CH3]+. The structures may be considered as composed of anionic inorganic sheets (2D blocks) and cationic organic blocks self-organized according to competing hydrophilic-hydrophobic interactions. Analysis of the structures allows us to conclude that the charge-density matching principle is observed in uranyl compounds. In order to satisfy some basic peculiarities of uranyl (in general, actinyl) chemistry, it requires specific additional mechanisms: (a) in long-chain-amine-templated compounds, protonated amine molecules inter-digitate; (b) in long-chain-diamine-templated compounds, incorporation of acid-water interlayers into an organic substructure is necessary; (c) the inclination angle of the amine chains may vary in order to modify
Density Dependence of Charge-4 Vortex Splitting in Bose–Einstein Condensates
Shibayama, Hitoshi; Tsukada, Akinori; Yoshihara, Takahisa; Kuwamoto, Takeshi
2016-05-01
We studied the axial-direction density dependence of the splitting of a charge-4 vortex created in 87Rb Bose–Einstein condensates. Vortices were generated by topological phase imprinting, and the axial density of the condensates was controlled by an optical potential. Linear and triangular arrangements of four single-charged vortices that emerged through the charge-4 vortex collapse were observed. The splitting of the charge-4 vortices was suppressed by maintaining the density outside the l = 2 unstable mode regions where linear arrangements were formed. In addition, we studied vortex dynamics in a high density region for which investigations have not been previously performed.
Constrained capacity management and cost minimisation of EV-charging in a parking garage
Kamphuis, I.G.; Macdougall, P.; Veen, W. van der; Bakker, E.; Velde, J. van de
2013-01-01
Apart from the optimal real-time electricity price to buy the electricity, the optimal, time dependent, capacity contracted with the DSO is of crucial importance for concerted charging of electric vehicles in a parking garage. The battery management system, on its turn, imposes constraints on the se
D. K. Narvilkar
1979-07-01
Full Text Available In the present paper, the equations of internal ballistics of composite charge consisting of N component charge with quadratic form are solved. Largange density approximation and hydrodynamic flow behaviour, have been assumed and the solutions are obtained for the composite charge for these assumptions.
LI Zhi-Bing; WANG Wei-Liang
2006-01-01
We derive the analytic solution of induced electrostatic potential along single wall carbon nanotubes. Under the hypothesis of constant density of states in the charge-neutral level, we are able to obtain the linear density of excess charge in an external Geld parallel to the tube axis.
Li, Zhibing; Wang, Weiliang
2006-01-01
We derived the analytic solution of induced electrostatic potential along single wall carbon nanotubes. Under the hypothesis of constant density of states in the charge-neutral level, we are able to obtain the linear density of excess charge in an external field parallel to the tube axis.
Farris, Stefano; Mora, Luigi; Capretti, Giorgio; Piergiovanni, Luciano
2012-01-01
An easy analytical method for determination of the charge density of polyelectrolytes, including polysaccharides and other biopolymers, is presented. The basic principles of conductometric titration, which is used in the pulp and paper industry as well as in colloid and interface science, were adapted to quantify the charge densities of a…
Tanner, D. B.; Cummings, K. D.; Jacobsen, Claus Schelde
1981-01-01
Detailed far-infrared measurements at temperatures from 25 to 300 K provide strong support for a charge-density-wave mechanism for the dc conductivity and microwave dielectric constant of tetrathiafulvalene tetracyanoquinodimethane (TTF-TCNQ). At low temperatures the charge-density wave is pinned...
Quantum coherent switch utilizing commensurate nanoelectrode and charge density periodicities
Harrison, Neil; Singleton, John; Migliori, Albert
2008-08-05
A quantum coherent switch having a substrate formed from a density wave (DW) material capable of having a periodic electron density modulation or spin density modulation, a dielectric layer formed onto a surface of the substrate that is orthogonal to an intrinsic wave vector of the DW material; and structure for applying an external spatially periodic electrostatic potential over the dielectric layer.
The charge form factors of elastic electron scattering for isotones with N=20 and N=28 are calculated using the phase-shift analysis method, with corresponding charge density distributions from relativistic mean-field theory. The results show that there are sharp variations at the inner parts of charge distributions with the proton number decreasing. The corresponding charge form factors are divided into two groups because of the unique properties of the s-states wave functions, though the proton numbers change uniformly in two isotonic chains. Meanwhile, the shift regularities of the minima are also discussed, and we give a clear relation between the minima of the charge form factors and the corresponding charge radii. This relation is caused by the diffraction effect of the electron. Under this conclusion, we calculate the charge density distributions and the charge form factors of the A=44 nuclei chain. The results are also useful for studying the central depression in light exotic nuclei. (authors)
Charge density waves in 1T-TaS2: an angle-resolved photoemission study
Clerc, F. [Institut de Physique, Universite de Neuchatel, Rue A.L. Breguet 1, CH-2000 Neuchatel (Switzerland); Bovet, M. [Institut de Physique, Universite de Neuchatel, Rue A.L. Breguet 1, CH-2000 Neuchatel (Switzerland); Berger, H. [Institut de Physique Appliquee, EPFL, CH-1015 Lausanne (Switzerland); Despont, L. [Institut de Physique, Universite de Neuchatel, Rue A.L. Breguet 1, CH-2000 Neuchatel (Switzerland); Koitzsch, C. [Institut de Physique, Universite de Neuchatel, Rue A.L. Breguet 1, CH-2000 Neuchatel (Switzerland); Garnier, M.G. [Institut de Physique, Universite de Neuchatel, Rue A.L. Breguet 1, CH-2000 Neuchatel (Switzerland); Aebi, P. [Institut de Physique, Universite de Neuchatel, Rue A.L. Breguet 1, CH-2000 Neuchatel (Switzerland)]. E-mail: philipp.aebi@unine.ch
2004-09-15
The transition metal dichalcogenide 1T-TaS2 is a layered material exhibiting charge density waves. Based on angle-resolved photoemission experiments mapping spectral weight at the Fermi surface and density functional theory calculations we discuss possible mechanisms involved with the creation of charge density waves. At first the flat parts of the elliptically shaped Fermi surface appear to play an important role via Fermi surface nesting. A closer analysis of the charge density wave induced new Brillouin zones and the possible energy balance between elastic deformation energy and electronic energy points to a more complicated scenario.
Charge density waves in 1T-TaS2: an angle-resolved photoemission study
The transition metal dichalcogenide 1T-TaS2 is a layered material exhibiting charge density waves. Based on angle-resolved photoemission experiments mapping spectral weight at the Fermi surface and density functional theory calculations we discuss possible mechanisms involved with the creation of charge density waves. At first the flat parts of the elliptically shaped Fermi surface appear to play an important role via Fermi surface nesting. A closer analysis of the charge density wave induced new Brillouin zones and the possible energy balance between elastic deformation energy and electronic energy points to a more complicated scenario
From super-charged nuclei to massive nuclear density cores
Popov, Vladimir
2010-01-01
Due to $e^+e^-$-pair production in the field of supercritical $(Z \\gg Z_{cr}\\approx 170 $) nucleus an electron shell, created out of the vacuum, is formed. The distribution of the vacuum charge in this shell has been determined for super-charged nuclei $Ze^3 \\ga 1$ within the framework of the Thomas-Fermi equation generalized to the relativistic case. For $Ze^3 \\gg 1$ the electron shell penetrates inside the nucleus and almost completely screens its charge. Inside such nucleus the potential takes a constant value equal to $V_0=-(3\\pi^2 n_p)^{1/3} \\sim -2m_{\\pi}c^2$, and super-charged nucleus represents an electrically neutral plasma consisting of $e,p$ and $n$. Near the edge of the nucleus a transition layer exists with a width $\\lambda \\approx \\alpha^{-1/2} \\hbar/m_{\\pi} c\\sim 15$ fm, which is independent of $Z~~ (\\hbar/m_{\\pi} c \\ll \\lambda \\ll \\hbar/m_e c)$. The electric field and surface charge are concentrated in this layer. These results, obtained earlier for hypothetical superheavy nuclei with $Z \\sim ...
Encircling the dark: constraining dark energy via cosmic density in spheres
Codis, S; Bernardeau, F; Uhlemann, C; Prunet, S
2016-01-01
The recently published analytic probability density function for the mildly non-linear cosmic density field within spherical cells is used to build a simple but accurate maximum likelihood estimate for the redshift evolution of the variance of the density, which, as expected, is shown to have smaller relative error than the sample variance. This estimator provides a competitive probe for the equation of state of dark energy, reaching a few percent accuracy on wp and wa for a Euclid-like survey. The corresponding likelihood function can take into account the configuration of the cells via their relative separations. A code to compute one-cell density probability density functions for arbitrary initial power spectrum, top-hat smoothing and various spherical collapse dynamics is made available online so as to provide straightforward means of testing the effect of alternative dark energy models and initial power-spectra on the low-redshift matter distribution.
Encircling the dark: constraining dark energy via cosmic density in spheres
Codis, S.; Pichon, C.; Bernardeau, F.; Uhlemann, C.; Prunet, S.
2016-08-01
The recently published analytic probability density function for the mildly non-linear cosmic density field within spherical cells is used to build a simple but accurate maximum likelihood estimate for the redshift evolution of the variance of the density, which, as expected, is shown to have smaller relative error than the sample variance. This estimator provides a competitive probe for the equation of state of dark energy, reaching a few per cent accuracy on wp and wa for a Euclid-like survey. The corresponding likelihood function can take into account the configuration of the cells via their relative separations. A code to compute one-cell-density probability density functions for arbitrary initial power spectrum, top-hat smoothing and various spherical-collapse dynamics is made available online, so as to provide straightforward means of testing the effect of alternative dark energy models and initial power spectra on the low-redshift matter distribution.
Bond charge approximation for valence electron density in elemental semiconductors
The spatial valence electron distribution in silicon and diamond is calculated in adiabatic bond charge approximation at zero temperature when bond charges have the Gaussian shape and their tensor character is taken into account. An agreement between theory and experiment has been achieved. For this purpose Xia's ionic pseudopotentials and Schulze-Unger's dielectric function are used. By two additional parameters Asub(B) and Zsub(B)sup(') we describe the spatial extent of the bond charge and local-field corrections, respectively. The parameter Zsub(B)sup(') accounts for the ratio between the Coulomb and exchange correlation interactions of the valence electrons and its silicon and diamond values have different signs. (author)
穆海宝; 张冠军
2011-01-01
Surface charges greatly affect the discharge/flashover development process across an insulator. The relationship between surface charge distribution on insulating materials and measurement data based on Pockels technique is discussed, and an improved algorithm is built to calculate the real surface charge density from original data. In this algorithm, two-dimensional Fourier transform technique and Wiener filter are employed to reduce the amount of numerical calculation and improve the stability of computation, Moreover, this algorithm considers not only the influence of sample＇s thickness and permittivity, but also the impact of charges at different positions. The achievement of this calibration algorithm is demonstrated in details. Compared with traditional algorithms, the improved one supplies a better solution in the calibration of surface charge distribution on different samples with different thickness.
Constraining snowmelt in a temperature-index model using simulated snow densities
Bormann, Kathryn J.
2014-09-01
Current snowmelt parameterisation schemes are largely untested in warmer maritime snowfields, where physical snow properties can differ substantially from the more common colder snow environments. Physical properties such as snow density influence the thermal properties of snow layers and are likely to be important for snowmelt rates. Existing methods for incorporating physical snow properties into temperature-index models (TIMs) require frequent snow density observations. These observations are often unavailable in less monitored snow environments. In this study, previous techniques for end-of-season snow density estimation (Bormann et al., 2013) were enhanced and used as a basis for generating daily snow density data from climate inputs. When evaluated against 2970 observations, the snow density model outperforms a regionalised density-time curve reducing biases from -0.027gcm-3 to -0.004gcm-3 (7%). The simulated daily densities were used at 13 sites in the warmer maritime snowfields of Australia to parameterise snowmelt estimation. With absolute snow water equivalent (SWE) errors between 100 and 136mm, the snow model performance was generally lower in the study region than that reported for colder snow environments, which may be attributed to high annual variability. Model performance was strongly dependent on both calibration and the adjustment for precipitation undercatch errors, which influenced model calibration parameters by 150-200%. Comparison of the density-based snowmelt algorithm against a typical temperature-index model revealed only minor differences between the two snowmelt schemes for estimation of SWE. However, when the model was evaluated against snow depths, the new scheme reduced errors by up to 50%, largely due to improved SWE to depth conversions. While this study demonstrates the use of simulated snow density in snowmelt parameterisation, the snow density model may also be of broad interest for snow depth to SWE conversion. Overall, the
Constraining variable density of ice shelves using wide-angle radar measurements
Drews, Reinhard; Brown, Joel; Matsuoka, Kenichi; Witrant, Emmanuel; Philippe, Morgane; Hubbard, Bryn; Pattyn, Frank
2016-04-01
The thickness of ice shelves, a basic parameter for mass balance estimates, is typically inferred using hydrostatic equilibrium, for which knowledge of the depth-averaged density is essential. The densification from snow to ice depends on a number of local factors (e.g., temperature and surface mass balance) causing spatial and temporal variations in density-depth profiles. However, direct measurements of firn density are sparse, requiring substantial logistical effort. Here, we infer density from radio-wave propagation speed using ground-based wide-angle radar data sets (10 MHz) collected at five sites on Roi Baudouin Ice Shelf (RBIS), Dronning Maud Land, Antarctica. We reconstruct depth to internal reflectors, local ice thickness, and firn-air content using a novel algorithm that includes traveltime inversion and ray tracing with a prescribed shape of the depth-density relationship. For the particular case of an ice-shelf channel, where ice thickness and surface slope change substantially over a few kilometers, the radar data suggest that firn inside the channel is about 5 % denser than outside the channel. Although this density difference is at the detection limit of the radar, it is consistent with a similar density anomaly reconstructed from optical televiewing, which reveals that the firn inside the channel is 4.7 % denser than that outside the channel. Hydrostatic ice thickness calculations used for determining basal melt rates should account for the denser firn in ice-shelf channels. The radar method presented here is robust and can easily be adapted to different radar frequencies and data-acquisition geometries.
We report on the investigation of magnetic field induced charge density waves and Hall coefficient sign reversal in a quasi-two-dimensional electronic system of highly oriented pyrolytic graphite under very strong magnetic field. The change of Hall sign coefficient from negative to positive occurs at low temperature and high magnetic field just after the charge density wave transition, suggesting the role of hole-like quasi-particles in this effect. Angular dependent measurements show that the charge density wave transition and Hall sign reversal fields follow the magnetic field component along the c-axis of graphite.
Influence of electric charge and modified gravity on density irregularities
Bhatti, M.Z. Ul Haq; Yousaf, Z. [University of the Punjab, Department of Mathematics, Lahore (Pakistan)
2016-04-15
This work aims to identify some inhomogeneity factors for a plane symmetric topology with anisotropic and dissipative fluid under the effects of both electromagnetic field as well as Palatini f(R) gravity. We construct the modified field equations, kinematical quantities, and mass function to continue our analysis. We have explored the dynamical quantities, conservation equations and modified Ellis equations with the help of a viable f(R) model. Some particular cases are discussed with and without dissipation to investigate the corresponding inhomogeneity factors. For a non-radiating scenario, we examine such factors as dust, and isotropic and anisotropic matter in the presence of charge. For a dissipative fluid, we investigate the inhomogeneity factor with a charged dust cloud. We conclude that the electromagnetic field increases the inhomogeneity in matter while the extra curvature terms make the system more homogeneous with the evolution of time. (orig.)
Influence of Electric Charge and Modified Gravity on Density Irregularities
Bhatti, M Zaeem Ul Haq
2016-01-01
This work aims to identify some inhomogeneity factors for plane symmetric topology with anisotropic and dissipative fluid under the effects of both electromagnetic field as well as Palatini $f(R)$ gravity. We construct the modified field equations, kinematical quantities and mass function to continue our analysis. We have explored the dynamical quantities, conservation equations and modified Ellis equations with the help of a viable $f(R)$ model. Some particular cases are discussed with and without dissipation to investigate the corresponding inhomogeneity factors. For non-radiating scenario, we examine such factors with dust, isotropic and anisotropic matter in the presence of charge. For dissipative fluid, we investigate the inhomogeneity factor with charged dust cloud. We conclude that electromagnetic field increases the inhomogeneity in matter while the extra curvature terms make the system more homogeneous with the evolution of time.
Melting Point Of Metals In Relation Io Electron Charge Density
Boczkal G.
2015-09-01
Full Text Available The concept of spatial criterion of the electron charge concentration is applied to determine the metal melting point. Based on the model proposed for bcc metals, a model for hcp metals and general form for others has been developed. To calculate the melting point, only structural data and atomic number are required. The obtained results show good consistency with the experimental data for metals with atomic number Z < 70.
Finite temperature bosonic charge and current densities in compactified cosmic string spacetime
Mohammadi, Azadeh
2015-01-01
In this paper we study the expectation values of the induced charge and current densities for a massive bosonic field with nonzero chemical potential in the geometry of a higher dimensional compactified cosmic string with magnetic fluxes, along the string core and also enclosed by the compactified direction, in thermal equilibrium at finite temperature $T$. These densities are calculated by decomposing them into the vacuum expectation values and finite temperature contributions coming from the particles and antiparticles. The only nonzero components correspond to the charge, azimuthal and axial current densities. By using the Abel-Plana formula, we decompose the components of the densities into the part induced by the cosmic string and the one by the compactification. The charge density is an odd function of the chemical potential and even periodic function of the magnetic flux with a period equal to the quantum flux. Moreover, the azimuthal (axial) current density is an even function of the chemical potentia...
Mining for elastic constants of intermetallics from the charge density landscape
There is a significant challenge in designing new materials for targeted properties based on their electronic structure. While in principle this goal can be met using knowledge of the electron charge density, the relationships between the density and properties are largely unknown. To help overcome this problem we develop a quantitative structure–property relationship (QSPR) between the charge density and the elastic constants for B2 intermetallics. Using a combination of informatics techniques for screening all the potentially relevant charge density descriptors, we find that C11 and C44 are determined solely from the magnitude of the charge density at its critical points, while C12 is determined by the shape of the charge density at its critical points. From this reduced charge density selection space, we develop models for predicting the elastic constants of an expanded number of intermetallic systems, which we then use to predict the mechanical stability of new systems. Having reduced the descriptors necessary for modeling elastic constants, statistical learning approaches may then be used to predict the reduced knowledge-based required as a function of the constituent characteristics
Fractal dimension of the topological charge density distribution in SU(2) lattice gluodynamics
Buividovich, P.V. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Institute for Theoretical and Experimental Physics ITEP, Moscow (Russian Federation); Kalaydzhyan, T. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Institute for Theoretical and Experimental Physics ITEP, Moscow (Russian Federation); Polikarpov, M.I. [Institute for Theoretical and Experimental Physics ITEP, Moscow (Russian Federation)
2011-11-15
We study the effect of cooling on the spatial distribution of the topological charge density in quenched SU(2) lattice gauge theory with overlap fermions. We show that as the gauge field configurations are cooled, the Hausdorff dimension of regions where the topological charge is localized gradually changes from d=2/3 towards the total space dimension. Hence the cooling procedure destroys some of the essential properties of the topological charge distribution. (orig.)
Determination of charge carrier mobility in doped low density polyethylene using DC transients
Khalil, M.Salah; Henk, Peter O; Henriksen, Mogens
1989-01-01
Charge carrier mobility was determined for plain and doped low-density polyethylene (LDPE) using DC transient currents. Barium titanate was used as a strongly polar dopant and titanium dioxide as a semiconductor dopant. The values of the mobility obtained were on the order of 10-10 cm2 v-1 s-1...... a factor of five. Charge trapping and space charge formation were modified by the introduction of titanium dioxide...
Wang, Huiyuan; Yang, Xiaohu; Zhang, Youcai; Shi, JingJing; Jing, Y P; Liu, Chengze; Li, Shijie; Kang, Xi; Gao, Yang
2016-01-01
A method we developed recently for the reconstruction of the initial density field in the nearby Universe is applied to the Sloan Digital Sky Survey Data Release 7. A high-resolution N-body constrained simulation (CS) of the reconstructed initial condition, with $3072^3$ particles evolved in a 500 Mpc/h box, is carried out and analyzed in terms of the statistical properties of the final density field and its relation with the distribution of SDSS galaxies. We find that the statistical properties of the cosmic web and the halo populations are accurately reproduced in the CS. The galaxy density field is strongly correlated with the CS density field, with a bias that depend on both galaxy luminosity and color. Our further investigations show that the CS provides robust quantities describing the environments within which the observed galaxies and galaxy systems reside. Cosmic variance is greatly reduced in the CS so that the statistical uncertainties can be controlled effectively even for samples of small volumes...
Structure of amorphous Ag/Ge/S alloys: experimentally constrained density functional study
Akola, J.; Beuneu, B.; Jones, R. O.; Jóvári, P.; Kaban, I.; Kolář, J.; Voleská, I.; Wágner, T.
2015-12-01
Density functional/molecular dynamics simulations have been performed to determine structural and other properties of amorphous Ag/Ge/S and Ge/S alloys. In the former, the calculations have been combined with experimental data (x-ray and neutron diffraction, extended x-ray absorption fine structure). Ag/Ge/As alloys have high ionic conductivity and are among the most promising candidates for future memristor technology. We find excellent agreement between the experimental results and large-scale (500 atoms) simulations in Ag/Ge/S, and we compare and contrast the structures of Ge/S and Ag/Ge/S. The calculated electronic structures, vibrational densities of states, ionic mobilities, and cavity distributions of the amorphous materials are discussed and compared with data on crystalline phases where available. The high mobility of Ag in solid state electrolyte applications is related to the presence of cavities and can occur via jumps to a neighbouring vacant site.
Zelinka, Jiří; Oral, Martin; Radlička, Tomáš
Brno: Institute of Scientific Instruments AS CR, v. v. i, 2014. s. 91. ISBN 978-80-87441-11-4. [International Conference on Charged Parrticle Optics /9./. 31.08.2014-05.09.2014, Brno] Institutional support: RVO:68081731 Keywords : space charge * current density evaluation * self-consistent computation * remeshing * FEM Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering
Charge density distribution of transparent p-type semiconductor (LaO)CuS
Takase, Kouichi; Sato,Ken; Shoji, Osamu; Takahashi, Yumiko; Takano, Yoshiki; Sekizawa, Kazuko; Kuroiwa, Yoshihiro; GOTO, MANABU
2007-01-01
The charge density distributions of layered oxysulfide (LaO)CuS, known as a p-type transparent semiconductor, have been investigated by analyzing the synchrotron radiation powder diffraction profile with the maximum entropy method/Rietveld method. The bonding character of the Cu–S bond is revealed to be covalent. Meanwhile, the O–La bonding has both ionic and covalent characters. The number of electrons estimated by integrating the charge density around each atom gave direct evidence that eac...
Photoinduced Dynamics in the Charge Density Wave Compound 4HB-TaSe2
Demsar J.
2013-03-01
Full Text Available We report on ultrafast photoindued charge density wave (CDW dynamics in the transition-metal dichalcogenide 4Hb-TaSe2, studied with ultrafast electron diffraction. Fluence dependence of the lattice superstructure suppression show a phase transition from the commensurate to the incommensurate phase of 4Hb-TaSe2. Unusually long recovery times of perturbed charge density waves indicate th importance of a coupling between the two dimensional CDWs.
Chiral anomaly, Charge Density Waves, and Axion Strings from Weyl Semimetals
Wang, Zhong; Zhang, Shou-Cheng
2012-01-01
We study dynamical instability and chiral symmetry breaking in three dimensional Weyl semimetals, which turns Weyl semimetals into "axion insulators". Charge density waves (CDW) is found to be the natural consequence of the chiral symmetry breaking. The phase mode of this charge density wave state is identified as the axion, which couples to electromagnetic field in the topological $\\theta{\\bf E}\\cdot{\\bf B}$ term. One of our main results is that the "axion strings" can be realized as the (sc...
Kumar, Amit; POUMIROL, Jean-Marie; Escoffier, Walter; Goiran, Michel; Raquet, Bertrand; Pivin, Jean Claude
2010-01-01
We report on the investigation of magnetic field induced charge density wave and Hall coefficient sign reversal in a quasi-two dimensional electronic system of highly oriented pyrolytic graphite under very strong magnetic field. The change of Hall sign coefficient from negative to positive occurs at low temperature and high magnetic field just after the charge density wave transition, suggesting the role of hole-like quasi-particles in this effect. Angular dependent measurements show that the...
Constraining the nuclear energy density functional with quantum Monte Carlo calculations
Roggero, Alessandro; Mukherjee, Abhishek; Pederiva, Francesco
2014-01-01
We study the problem of an impurity in fully polarized (spin-up) low density neutron matter with the help of an accurate quantum Monte Carlo method in conjunction with a realistic nucleon-nucleon interaction derived from chiral effective field theory at next-to-next-to-leading-order. Our calculations show that the behavior of the proton spin-down impurity is very similar to that of a polaron in a fully polarized unitary Fermi gas. We show that our results can be used to put tight constraints ...
Mohammadi, A; Saharian, A A
2014-01-01
We investigate the finite temperature expectation values of the charge and current densities for a massive fermionic field with nonzero chemical potential, $\\mu$, in the geometry of a straight cosmic string with a magnetic flux running along its axis. These densities are decomposed into the vacuum expectation values and contributions coming from the particles and antiparticles. The charge density is an even periodic function of the magnetic flux with the period equal to the quantum flux and an odd function of the chemical potential. The only nonzero component of the current density corresponds to the azimuthal current. The latter is an odd periodic function of the magnetic flux and an even function of the chemical potential. At high temperatures, the parts in the charge density and azimuthal current induced by the planar angle deficit and magnetic flux are exponentially small. The asymptotic behavior at low temperatures crucially depends whether the value $|\\mu|$ is larger or smaller than the mass of the fiel...
Yongjun Ahn
Full Text Available The charging infrastructure location problem is becoming more significant due to the extensive adoption of electric vehicles. Efficient charging station planning can solve deeply rooted problems, such as driving-range anxiety and the stagnation of new electric vehicle consumers. In the initial stage of introducing electric vehicles, the allocation of charging stations is difficult to determine due to the uncertainty of candidate sites and unidentified charging demands, which are determined by diverse variables. This paper introduces the Estimating the Required Density of EV Charging (ERDEC stations model, which is an analytical approach to estimating the optimal density of charging stations for certain urban areas, which are subsequently aggregated to city level planning. The optimal charging station's density is derived to minimize the total cost. A numerical study is conducted to obtain the correlations among the various parameters in the proposed model, such as regional parameters, technological parameters and coefficient factors. To investigate the effect of technological advances, the corresponding changes in the optimal density and total cost are also examined by various combinations of technological parameters. Daejeon city in South Korea is selected for the case study to examine the applicability of the model to real-world problems. With real taxi trajectory data, the optimal density map of charging stations is generated. These results can provide the optimal number of chargers for driving without driving-range anxiety. In the initial planning phase of installing charging infrastructure, the proposed model can be applied to a relatively extensive area to encourage the usage of electric vehicles, especially areas that lack information, such as exact candidate sites for charging stations and other data related with electric vehicles. The methods and results of this paper can serve as a planning guideline to facilitate the extensive
Wang, Yongjia; Li, Qingfeng; Zhang, Hongfei; Leifels, Y; Trautmann, W
2014-01-01
Within the newly updated version of the ultrarelativistic quantum molecular dynamics (UrQMD) model, the transverse-velocity dependence of the elliptic flow of free nucleons from $^{197}$Au+$^{197}$Au collisions at the incident energy 400 MeV$/$nucleon is studied within different windows of the normalized c.m. rapidity $y_0$. It is found that the elliptic flow difference $v_{2}^{n}$-$v_{2}^{p}$ and ratio $v_{2}^{n}$/$v_{2}^{p}$ of neutrons versus protons are sensitive to the density dependence of the symmetry energy, especially the ratio $v_{2}^{n}$/$v_{2}^{p}$ at small transverse velocity in the intermediate rapidity intervals $0.4<|y_0|<0.6$. By comparing either transverse-momentum dependent or integrated FOPI/LAND elliptic flow data of nucleons and hydrogen isotopes with calculations using various Skyrme interactions, all exhibiting similar values of isoscalar incompressibility but very different density dependences of the symmetry energy, a moderately soft to linear symmetry energy is extracted, in g...
Supergravity and the jet quenching parameter in the presence of R-charge densities
Avramis, S D; Avramis, Spyros D.; Sfetsos, Konstadinos
2007-01-01
We employ the AdS/CFT correspondence to compute the jet quenching parameter for N=4 Yang-Mills theory at nonzero R-charge densities. Using as dual supergravity backgrounds non-extremal rotating branes, we find that the presence of the R-charges generically enhances the jet quenching phenomenon. However, at fixed temperature, this enhancement might or might not be a monotonically increasing function of the R-charge density and depends on the number of independent angular momenta describing the solution. We perform our analysis for the canonical as well as for the grand canonical ensemble which give qualitatively similar results.
Charge transfer states around the donor–acceptor interface in an organic solar cell determine the device performance in terms of the open circuit voltage. In the present work, we propose a computational scheme based on constrained density functional tight binding theory (c-DFTB) to assess the energy of the lowest charge transfer (CT) state in such systems. A comparison of the c-DFTB scheme with Hartree–Fock based configuration interaction of singles (CIS) and with time-dependent density functional theory (TD-DFT) using the hybrid functional B3LYP reveals that CIS and c-DFTB reproduce the correct Coulomb asymptotics between cationic donor and anionic acceptor configurations, whereas TD-DFT gives a qualitatively wrong excitation energy. Together with an embedding scheme accounting for the polarizable medium, this c-DFTB scheme is applied to several donor–acceptor combinations used in molecular solar cells. The external quantum efficiency of photovoltaic cells based on zinc phthalocyanine–C60 blends reveals a CT band remaining much narrower than the density of states of acceptor HOMO and donor LUMO, an observation which can be interpreted in a natural way in terms of Marcus transfer theory. A detailed comparison with c-DFTB calculations reveals an energy difference of 0.32 eV between calculated and observed absorption from the electronic ground state into the CT state. In a blend of a functionalized thiophene and C60, the photoluminescence spectra differ significantly from neat films, allowing again an assignment to CT states. The proposed computational scheme reproduces the observed trends of the observed open circuit voltages in photovoltaic devices relying on several donor–acceptor blends, finding an offset of 1.16 eV on average. This value is similar as in polymer–fullerene photovoltaic systems where it amounts to about 0.9 eV, indicating that the photophysics of CT states in molecular donor–acceptor blends and in polymer–fullerene blends are
An extended force density method for form finding of constrained cable nets
Ghada Aboul-Nasr
2015-06-01
This paper studied the prestressed cable nets and the loaded cable nets. For prestressed cable nets, coordinate constraints to all nodes of the cable net are introduced to modify the shape after graphically examining the preliminary shape. This preliminary shape resulted from linear analysis of assumed distribution of cable force densities. For analyzing cable nets under different load cases, the first load case is analyzed to achieve the coordinate constraints assigned to nodes. Analysis results are node coordinates, cable forces and lengths. Young’s modulus and areas of cables are used to calculate the unstressed length of all cables using materialization equations, those lengths are used as constraint in the analysis of other load cases. Forces in all cables under different load cases/combinations are calculated. By using this approach, design of cable net under static load is simplified.
Inhomogeneity of charge-density-wave order and quenched disorder in a high-Tc superconductor
Campi, G.; Bianconi, A.; Poccia, N.; Bianconi, G.; Barba, L.; Arrighetti, G.; Innocenti, D.; Karpinski, J.; Zhigadlo, N. D.; Kazakov, S. M.; Burghammer, M.; Zimmermann, M. V.; Sprung, M.; Ricci, A.
2015-09-01
It has recently been established that the high-transition-temperature (high-Tc) superconducting state coexists with short-range charge-density-wave order and quenched disorder arising from dopants and strain. This complex, multiscale phase separation invites the development of theories of high-temperature superconductivity that include complexity. The nature of the spatial interplay between charge and dopant order that provides a basis for nanoscale phase separation remains a key open question, because experiments have yet to probe the unknown spatial distribution at both the nanoscale and mesoscale (between atomic and macroscopic scale). Here we report micro X-ray diffraction imaging of the spatial distribution of both short-range charge-density-wave `puddles' (domains with only a few wavelengths) and quenched disorder in HgBa2CuO4 + y, the single-layer cuprate with the highest Tc, 95 kelvin (refs 26, 27, 28). We found that the charge-density-wave puddles, like the steam bubbles in boiling water, have a fat-tailed size distribution that is typical of self-organization near a critical point. However, the quenched disorder, which arises from oxygen interstitials, has a distribution that is contrary to the usually assumed random, uncorrelated distribution. The interstitial-oxygen-rich domains are spatially anticorrelated with the charge-density-wave domains, because higher doping does not favour the stripy charge-density-wave puddles, leading to a complex emergent geometry of the spatial landscape for superconductivity.
Inhomogeneity of charge-density-wave order and quenched disorder in a high-Tc superconductor.
Campi, G; Bianconi, A; Poccia, N; Bianconi, G; Barba, L; Arrighetti, G; Innocenti, D; Karpinski, J; Zhigadlo, N D; Kazakov, S M; Burghammer, M; Zimmermann, M v; Sprung, M; Ricci, A
2015-09-17
It has recently been established that the high-transition-temperature (high-Tc) superconducting state coexists with short-range charge-density-wave order and quenched disorder arising from dopants and strain. This complex, multiscale phase separation invites the development of theories of high-temperature superconductivity that include complexity. The nature of the spatial interplay between charge and dopant order that provides a basis for nanoscale phase separation remains a key open question, because experiments have yet to probe the unknown spatial distribution at both the nanoscale and mesoscale (between atomic and macroscopic scale). Here we report micro X-ray diffraction imaging of the spatial distribution of both short-range charge-density-wave 'puddles' (domains with only a few wavelengths) and quenched disorder in HgBa2CuO4 + y, the single-layer cuprate with the highest Tc, 95 kelvin (refs 26-28). We found that the charge-density-wave puddles, like the steam bubbles in boiling water, have a fat-tailed size distribution that is typical of self-organization near a critical point. However, the quenched disorder, which arises from oxygen interstitials, has a distribution that is contrary to the usually assumed random, uncorrelated distribution. The interstitial-oxygen-rich domains are spatially anticorrelated with the charge-density-wave domains, because higher doping does not favour the stripy charge-density-wave puddles, leading to a complex emergent geometry of the spatial landscape for superconductivity. PMID:26381983
Finite temperature bosonic charge and current densities in compactified cosmic string spacetime
Mohammadi, A.; Bezerra de Mello, E. R.
2016-06-01
In this paper, we study the expectation values of the induced charge and current densities for a massive bosonic field with nonzero chemical potential in the geometry of a higher-dimensional compactified cosmic string with magnetic fluxes along the string core and also enclosed by the compactified direction in thermal equilibrium at finite temperature T . These densities are calculated by decomposing them into the vacuum expectation values and finite temperature contributions coming from the particles and antiparticles. The only nonzero components correspond to the charge, azimuthal, and axial current densities. By using the Abel-Plana formula, we decompose the components of the densities into the part induced by the cosmic string and the one by the compactification. The charge density is an odd function of the chemical potential and even periodic function of the magnetic flux with a period equal to the quantum flux. Moreover, the azimuthal (axial) current density is an even function of the chemical potential and an odd (even) periodic function of the magnetic flux with the same period. In this paper, our main concern is the thermal effect on the charge and current densities, including some limiting cases, the low- and high-temperature approximations. We show that in all cases, the temperature enhances the induced densities.
d-Density Wave Scenario Description of the New Hidden Charge Order in Cuprates
Makhfudz, Imam
2016-06-01
In this paper, we show that the theory of high Tc superconductivity based on a microscopic model with d-density wave (DDW) scenario in the pseudogap phase is able to reproduce some of the most important features of the recent experimentally discovered hidden charge order in several families of Cuprates. In particular, by computing and comparing energies of charge orders of different modulation directions derived from a full microscopic theory with d-density wave scenario, the axial charge order ϕX(Y) with wavevector {Q} = (Q0,0)((0,Q0)) is shown to be unambiguously energetically more favorable over the diagonal charge order ϕX±Y with wavevector {Q} = (Q0, ± Q0) at least in commensurate limit, to be expected also to hold even to more general incommensurate case, in agreement with experiment. The two types of axial charge order ϕX and ϕY are degenerate by symmetry. We find that within the superconducting background, biaxial (checkerboard) charge order is energetically more favorable than uniaxial (stripe) charge order, and therefore checkerboard axial charge order should be the one observed in experiments, assuming a single domain of charge ordered state on each CuO2 plane.
S Haddad
2010-09-01
The influence of the isovector coupling channel on the central depression parameter and the central value of the charge density distribution in heavy spherical nuclei was studied. The isovector coupling channel leads to about 50% increase of the central depression parameter, and weakens the dependency of both central depression parameter and central density on the asymmetry, impressively contributing to the semibubble form of the charge density distribution in heavy nuclei, and increasing the probability of larger nuclei with higher proton numbers and higher neutron-to-proton ratios stable.
The influence of the isovector coupling channel on the central depression parameter and the central value of the charge density distribution in heavy spherical nuclei was studied. The isovector coupling channel leads to about 50% increase of the central depression parameter, and weakens the dependency of both central depression parameter and the central density on the asymmetry, impressively contributing to the semibubble form of the charge density distribution in heavy nuclei, and increasing the probability of larger nuclei with higher proton numbers and higher neutron-to-proton ratios stable. (author)
Low Density Phases in a Uniformly Charged Liquid
Knüpfer, Hans; Muratov, Cyrill B.; Novaga, Matteo
2016-07-01
This paper is concerned with the macroscopic behavior of global energy minimizers in the three-dimensional sharp interface unscreened Ohta-Kawasaki model of diblock copolymer melts. This model is also referred to as the nuclear liquid drop model in the studies of the structure of highly compressed nuclear matter found in the crust of neutron stars, and, more broadly, is a paradigm for energy-driven pattern forming systems in which spatial order arises as a result of the competition of short-range attractive and long-range repulsive forces. Here we investigate the large volume behavior of minimizers in the low volume fraction regime, in which one expects the formation of a periodic lattice of small droplets of the minority phase in a sea of the majority phase. Under periodic boundary conditions, we prove that the considered energy {Γ}-converges to an energy functional of the limit "homogenized" measure associated with the minority phase consisting of a local linear term and a non-local quadratic term mediated by the Coulomb kernel. As a consequence, asymptotically the mass of the minority phase in a minimizer spreads uniformly across the domain. Similarly, the energy spreads uniformly across the domain as well, with the limit energy density minimizing the energy of a single droplet per unit volume. Finally, we prove that in the macroscopic limit the connected components of the minimizers have volumes and diameters that are bounded above and below by universal constants, and that most of them converge to the minimizers of the energy divided by volume for the whole space problem.
Hoeng, Fanny; Denneulin, Aurore [Université Grenoble Alpes, LGP2 (France); Neuman, Charles [Poly-Ink (France); Bras, Julien, E-mail: julien.bras@grenoble-inp.fr [Université Grenoble Alpes, LGP2 (France)
2015-06-15
Synthesis of silver nanoparticles using cellulose nanocrystals (CNC) has been found to be a great method for producing metallic particles in a sustainable way. In this work, we propose to evaluate the influence of the charge density of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-oxidized CNC on the morphology and the stability of synthetized silver nanoparticles. Silver nanoparticles were obtained by sol–gel reaction using borohydride reduction, and charge density of TEMPO-oxidized CNC was tuned by an amine grafting. The grafting was performed at room temperature and neutral pH. Crystallinity and morphology were kept intact during the peptidic reaction on CNC allowing knowing the exact impact of the charge density. Charge density has been found to have a strong impact on shape, organization, and suspension stability of resulting silver particles. Results show an easy way to tune the charge density of CNC and propose a sustainable way to control the morphology and stability of silver nanoparticles in aqueous suspension.
Ghasemi, S. Alireza; Hofstetter, Albert; Saha, Santanu; Goedecker, Stefan
2015-07-01
Based on an analysis of the short-range chemical environment of each atom in a system, standard machine-learning-based approaches to the construction of interatomic potentials aim at determining directly the central quantity, which is the total energy. This prevents, for instance, an accurate description of the energetics of systems in which long-range charge transfer or ionization is important. We propose therefore not to target directly with machine-learning methods the total energy but an intermediate physical quantity, namely, the charge density, which then in turn allows us to determine the total energy. By allowing the electronic charge to distribute itself in an optimal way over the system, we can describe not only neutral but also ionized systems with unprecedented accuracy. We demonstrate the power of our approach for both neutral and ionized NaCl clusters where charge redistribution plays a decisive role for the energetics. We are able to obtain chemical accuracy, i.e., errors of less than a millihartree per atom compared to the reference density functional results for a huge data set of configurations with large structural variety. The introduction of physically motivated quantities which are determined by the short-range atomic environment via a neural network also leads to an increased stability of the machine-learning process and transferability of the potential.
Suppression of Three-Dimensional Charge Density Wave Ordering via Thickness Control
Kim, Gideok; Neumann, Michael; Kim, Minu; Le, Manh Duc; Kang, Tae Dong; Noh, Tae Won
2015-11-01
Barium bismuth oxide (BaBiO3 ) is the end member of two families of high-Tc superconductors, i.e., BaPb1 -xBix O3 and Ba1 -xKx BiO3 . The undoped parent compound is an insulator, exhibiting a charge density wave that is strongly linked to a static breathing distortion in the oxygen sublattice of the perovskite structure. We report a comprehensive spectroscopic and x-ray diffraction study of BaBiO3 thin films, showing that the minimum film thickness required to stabilize the breathing distortion and charge density wave is ≈11 unit cells, and that both phenomena are suppressed in thinner films. Our results constitute the first experimental observation of charge density wave suppression in bismuthate compounds without intentionally introducing dopants.
Elastic anomalies at the charge density wave transition in TbTe3
Saint-Paul, M.; Guttin, C.; Lejay, P.; Remenyi, G.; Leynaud, O.; Monceau, P.
2016-05-01
The set of elastic constants of the charge density wave (CDW) rare earth tritelluride TbTe3 has been measured at 15 MHz in the temperature range 300-360 K. Large anomalies in the velocity and ultrasonic attenuation of the longitudinal C11 and C33 modes are observed at the charge density wave phase transition TCDW=333 K. Anisotropic stress dependence ∂TCDW / ∂σ is found, the components ∂TCDW / ∂σ11 and ∂TCDW / ∂σ33 in the (a,c) plane are one order of magnitude larger than the component ∂TCDW / ∂σ22 perpendicular to it. The Landau theory has been used to explain the experimental data. Critical behaviour near the charge density wave phase transition is described in terms of a phenomenological dynamic scaling theory.
Full charge-density calculation of the surface energy of metals
Vitos, Levente; Kollár, J..; Skriver, Hans Lomholt
1994-01-01
We have calculated the surface energy and the work function of the 4d metals by means of an energy functional based on a self-consistent, spherically symmetric atomic-sphere potential. In this approach the kinetic energy is calculated completely within the atomic-sphere approximation (ASA) by means...... of a spherically symmetrized charge density, while the Coulomb and exchange-correlation contributions are calculated by means of the complete, nonspherically symmetric charge density within nonoverlapping, space-filling Wigner-Seitz cells. The functional is used to assess the convergence and the...... accuracy of the linear-muffin-tin-orbitals (LMTO) method and the ASA in surface calculations. We find that the full charge-density functional improves the agreement with recent full-potential LMTO calculations to a level where the average deviation in surface energy over the 4d series is down to 10%....
Zhou Dai Mei; Sá Ben-Hao; Li Zhong Dao
2002-01-01
Using a hadron and string cascade model, JPCIAE, and the corresponding Monte Carlo events generator, the energy and centrality dependences of charged particle pseudorapidity density in relativistic nuclear collisions were studied. Within the framework of this model, both the relativistic p anti p experimental data and the PHOBOS and PHENIX Au + Au data could be reproduced fairly well without retuning the model parameters. The author shows that since is not a well defined physical variable both experimentally and theoretically, the charged particle pseudorapidity density per participant pair can increase and also can decrease with increasing of , so it may be hard to use charged particle pseudorapidity density per participant pair as a function of to distinguish various theoretical models for particle production
Using a hadron and string cascade model, JPCIAE, and the corresponding Monte Carlo events generator, the energy and centrality dependences of charged particle pseudorapidity density in relativistic nuclear collisions were studied. Within the framework of this model, both the relativistic p anti p experimental data and the PHOBOS and PHENIX Au + Au data could be reproduced fairly well without retuning the model parameters. The author shows that since part> is not a well defined physical variable both experimentally and theoretically, the charged particle pseudorapidity density per participant pair can increase and also can decrease with increasing of part>, so it may be hard to use charged particle pseudorapidity density per participant pair as a function of part> to distinguish various theoretical models for particle production
Trapped charge densities in Al2O3-based silicon surface passivation layers
Jordan, Paul M.; Simon, Daniel K.; Mikolajick, Thomas; Dirnstorfer, Ingo
2016-06-01
In Al2O3-based passivation layers, the formation of fixed charges and trap sites can be strongly influenced by small modifications in the stack layout. Fixed and trapped charge densities are characterized with capacitance voltage profiling and trap spectroscopy by charge injection and sensing, respectively. Al2O3 layers are grown by atomic layer deposition with very thin (˜1 nm) SiO2 or HfO2 interlayers or interface layers. In SiO2/Al2O3 and HfO2/Al2O3 stacks, both fixed charges and trap sites are reduced by at least a factor of 5 compared with the value measured in pure Al2O3. In Al2O3/SiO2/Al2O3 or Al2O3/HfO2/Al2O3 stacks, very high total charge densities of up to 9 × 1012 cm-2 are achieved. These charge densities are described as functions of electrical stress voltage, time, and the Al2O3 layer thickness between silicon and the HfO2 or the SiO2 interlayer. Despite the strong variation of trap sites, all stacks reach very good effective carrier lifetimes of up to 8 and 20 ms on p- and n-type silicon substrates, respectively. Controlling the trap sites in Al2O3 layers opens the possibility to engineer the field-effect passivation in the solar cells.
Correlation between the extent of catalytic activity and charge density of montmorillonites.
Ertem, Gözen; Steudel, Annett; Emmerich, Katja; Lagaly, Gerhard; Schuhmann, Rainer
2010-09-01
The clay mineral montmorillonite is a member of the phyllosilicate group of minerals, which has been detected on martian soil. Montmorillonite catalyzes the condensation of activated monomers to form RNA-like oligomers. Extent of catalysis, that is, the yield of oligomers, and the length of the longest oligomer formed in these reactions widely varies with the source of montmorillonite (i.e., the locality where the mineral is mined). This study was undertaken to establish whether there exists a correlation between the extent of catalytic property and the charge density of montmorillonites. Charge density was determined by saturating the montmorillonites with alkyl ammonium cations that contained increasing lengths of alkyl chains, [CH₃-(CH₂)(n)-NH₃](+), where n = 3-16 and 18, and then measuring d(₀₀₁), interlayer spacing of the resulting montmorillonite-alkyl ammonium-montmorillonite complex by X-ray diffractometry (XRD). Results demonstrate that catalytic activity of montmorillonites with lower charge density is superior to that of higher charge density montmorillonite. They produce longer oligomers that contain 9 to 10 monomer units, while montmorillonite with high charge density catalyzes the formation of oligomers that contain only 4 monomer units. The charge density of montmorillonites can also be calculated from the chemical composition if elemental analysis data of the pure mineral are available. In the next mission to Mars, CheMin (Chemistry and Mineralogy), a combined X-ray diffraction/X-ray fluorescence instrument, will provide information on the mineralogical and elemental analysis of the samples. Possible significance of these results for planning the future missions to Mars for the search of organic compounds and extinct or extant life is discussed. PMID:20854214
Miranda Carreño, Rubén; Blanco Suárez, Ángeles; Fuente González, Elena de la; Negro Álvarez, Carlos Manuel
2008-01-01
The effect of charge density of 5 cationic polyacrylamides (C-PAMs)and 3 anionic polyacrylamides (A-PAMs) in single and in dual treatments with a coagulant on the flocculation and removal of dissolved and colloidal material by dissolved air flotation (DAF) in papermaking has been studied. In single systems, good results were achieved both with low and high charge C-PAMs(1.0and 3.0–3.5 meq/g). In dual sy tems, high charge C-PAMs (3.0–3.5 meq/g)and A-PAMs (1.5 meq/g), were the most efficient. R...
X-ray diffraction studies of charge density waves in cuprate superconductors: A brief review
High temperature superconductivity in the cuprates has fascinated scientists for more than 25 years, but there is still no consensus on the pairing mechanism. Soon after the discovery of high temperature superconductivity, it was suggested that the cuprates have an incipient tendency towards spatial electronic order – spin and charge order. In this paper, I will review X-ray diffraction studies of charge density waves in the cuprates. These results, by a number of different groups, indicate that short-range charge correlations exist across the cuprate family, and in many cases are clearly competing with the superconductivity
Effect of ground state correlations on the charge transition densities of vibrational states
The effect of ground state correlations on the charge transition densities of vibrational states in spherical nuclei is studied. The problem for the ground state correlations beyond RPA leads to a non-linear system of equations, which is solved numerically. The influence of the correlations on the pairing is taken into account too. The inclusion of ground state correlations beyond RPA results in an essential suppression of the charge transition density in the nuclear interior in comparison with the RPA calculations and enables one to reproduce the experimental data. 30 refs., 7 figs., 3 tabs
Laktionov, Andrey; Chemineau-Chalaye, Emilie; Wesolowski, Tomasz A
2016-08-21
Besides molecular electron densities obtained within the Born-Oppenheimer approximation (ρB(r)) to represent the environment, the ensemble averaged density (〈ρB〉(r)) is also admissible in frozen-density embedding theory (FDET) [Wesolowski, Phys. Rev. A, 2008, 77, 11444]. This makes it possible to introduce an approximation in the evaluation of the solvent effect on quantum mechanical observables consisting of replacing the ensemble averaged observable by the observable evaluated at ensemble averaged ρB(r). This approximation is shown to affect negligibly the solvatochromic shift in the absorption of hydrated acetone. The proposed model provides a continuum type of representation of the solvent, which reflects nevertheless its local structure, and it is to be applied as a post-simulation analysis tool in atomistic level simulations. PMID:26984532
Spatially separated charge densities of electrons and holes in organic-inorganic halide perovskites
Solution-processable methylammonium lead trihalide perovskites exhibit remarkable high-absorption and low-loss properties for solar energy conversion. Calculation from density functional theory indicates the presence of non-equivalent halogen atoms in the unit cell because of the specific orientation of the organic cation. Considering the 〈100〉 orientation as an example, I1, one of the halogen atoms, differs from the other iodine atoms (I2 and I3) in terms of its interaction with the organic cation. The valance-band-maximum (VBM) and conduction-band-minimum (CBM) states are derived mainly from 5p orbital of I1 atom and 6p orbital of Pb atom, respectively. The spatially separated charge densities of the electrons and holes justify the low recombination rate of the pure iodide perovskite. Chlorine substitution further strengthens the unique position of the I1 atom, leading to more localized charge density around the I1 atom and less charge density around the other atoms at the VBM state. The less overlap of charge densities between the VBM and CBM states explains the relatively lower carrier recombination rate of the iodine-chlorine mixed perovskite. Chlorine substitution significantly reduces the effective mass at a direction perpendicular to the Pb-Cl bond and organic axis, enhancing the carrier transport property of the mixed perovskite in this direction
Spatially separated charge densities of electrons and holes in organic-inorganic halide perovskites
Li, Dan; Liang, Chunjun, E-mail: chjliang@bjtu.edu.cn, E-mail: zhqhe@bjtu.edu.cn; Zhang, Huimin; You, Fangtian; He, Zhiqun, E-mail: chjliang@bjtu.edu.cn, E-mail: zhqhe@bjtu.edu.cn [Key Laboratory of Luminescence and Optical Information, Ministry of Education, School of Science, Beijing Jiaotong University, Beijing 100044 (China); Zhang, Chunxiu [Information Recording Materials Lab, Beijing Institute of Graphic Communication, Beijing 102600 (China)
2015-02-21
Solution-processable methylammonium lead trihalide perovskites exhibit remarkable high-absorption and low-loss properties for solar energy conversion. Calculation from density functional theory indicates the presence of non-equivalent halogen atoms in the unit cell because of the specific orientation of the organic cation. Considering the 〈100〉 orientation as an example, I{sub 1}, one of the halogen atoms, differs from the other iodine atoms (I{sub 2} and I{sub 3}) in terms of its interaction with the organic cation. The valance-band-maximum (VBM) and conduction-band-minimum (CBM) states are derived mainly from 5p orbital of I{sub 1} atom and 6p orbital of Pb atom, respectively. The spatially separated charge densities of the electrons and holes justify the low recombination rate of the pure iodide perovskite. Chlorine substitution further strengthens the unique position of the I{sub 1} atom, leading to more localized charge density around the I{sub 1} atom and less charge density around the other atoms at the VBM state. The less overlap of charge densities between the VBM and CBM states explains the relatively lower carrier recombination rate of the iodine-chlorine mixed perovskite. Chlorine substitution significantly reduces the effective mass at a direction perpendicular to the Pb-Cl bond and organic axis, enhancing the carrier transport property of the mixed perovskite in this direction.
Induced fermionic charge and current densities in two-dimensional rings
Bellucci, S; Grigoryan, A Kh
2016-01-01
For a massive quantum fermionic field, we investigate the vacuum expectation values (VEVs) of the charge and current densities induced by an external magnetic flux in a two-dimensional circular ring. Both the irreducible representations of the Clifford algebra are considered. On the ring edges the bag (infinite mass) boundary conditions are imposed for the field operator. This leads to the Casimir type effect on the vacuum characteristics. The radial current vanishes. The charge and the azimuthal current are decomposed into the boundary-free and boundary-induced contributions. Both these contributions are odd periodic functions of the magnetic flux with the period equal to the flux quantum. An important feature that distinguishes the VEVs of the charge and current densities from the VEV of the energy density, is their finiteness on the ring edges. The current density is equal to the charge density for the outer edge and has the opposite sign on the inner edge. The VEVs are peaked near the inner edge and, as f...
Density decrease in vanadium-base alloys irradiated in the dynamic helium charging experiment
Chung, H.M.; Galvin, T.M.; Smith, D.L. [Argonne National Laboratory, Chicago, IL (United States)
1996-04-01
Combined effects of dynamically charged helium and neutron damage on density decrease (swelling) of V-4Cr-4Ti, V-5Ti, V-3Ti-1Si, and V-8Cr-6Ti alloys have been determined after irradiation to 18-31 dpa at 425-600{degrees}C in the Dynamic helium Charging Experiment (DHCE). To ensure better accuracy in density measurement, broken pieces of tensile specimens {approx} 10 times heavier than a transmission electron microscopy (TEM) disk were used. Density increases of the four alloys irradiated in the DHCE were <0.5%. This small change seems to be consistent with the negligible number density of microcavities characterized by TEM. Most of the dynamically produced helium atoms seem to have been trapped in the grain matrix without significant cavity nucleation or growth.
Bellucci, S; Bragança, E; Saharian, A A
2016-01-01
We evaluate the fermion condensate and the expectation values of the charge and current densities for a massive fermionic field in (2+1)-dimensional conical spacetime with a magnetic flux located at the cone apex. The consideration is done for both irreducible representations of the Clifford algebra. The expectation values are decomposed into the vacuum expectation values and contributions coming from particles and antiparticles. All these contributions are periodic functions of the magnetic flux with the period equal to the flux quantum. Related to the non-invariance of the model under the parity and time-reversal transformations, the fermion condensate and the charge density have indefinite parity with respect to the change of the signs of the magnetic flux and chemical potential. The expectation value of the radial current density vanishes. The azimuthal current density is the same for both the irreducible representations of the Clifford algebra. It is an odd function of the magnetic flux and an even funct...
A High Power Density Three-level Parallel Resonant Converter for Capacitor Charging
Sheng, Honggang
2009-01-01
This dissertation proposes a high-power, high-frequency and high-density three-level parallel resonant converter for capacitor charging. DC-DC pulsed power converters are widely used in military and medical systems, where the power density requirement is often stringent. The primary means for reducing the power converter size has been to reduce loss for reduced cooling systems and to increase the frequency for reduced passive components. Three-level resonant converters, which combine the mer...
Bambery, K.R.; Fleming, R.J.; Holbøll, Joachim
2001-01-01
Laser induced pressure pulse space charge measurements were made on 1.5 mm thick plaques of high purity low density polyethylene equipped with vacuum-evaporated aluminium electrodes. Temperature differences up to 20 °C were maintained across the samples, which were subjected to dc fields up to 1...
Equation of state for the detonation products of hexanitrostilbene at various charge densities
Lee, E. L.; Walton, J. R.; Kramer, P. E.
1976-05-01
An extensive description of the detonation behavior for the unique and useful high explosive hexanitrostilbene (HNS) is presented. To accomplish this the necessary experimental results measured by detonation of the pure material at charge densities of 1.00, 1.20, 1.40, 1.60, and 1.65 (g/cm/sup 3/ = Mg/m/sup 3/) were compiled and evaluated. Estimates of the equation of state of the detonation products were made for each charge density. To confirm these estimates two-dimensional hydrodynamic (HEMP code) calculations to simulate the cylinder test experiments for two charge densities of 1.2 and 1.6 Mg/m/sup 3/ were carried out. Detailed comparisons of the calculational and experimental results were made for these two tests. Interpolation and extrapolation of the equation of state parameters provided final estimates for the other charge densities. The results are summarized in five sets of Chapman-Jouguet parameters and JWL equation of state coefficients.
Scanning tunneling microscopy in TTF-TCNQ: Phase and amplitude modulated charge density waves
Wang, Z.Z.; Gorard, J.C.; Pasquier, C.; Jerome, D.; Bechgaard, K.
2003-01-01
Charge density waves (CDWs) have been studied at the surface of a cleaved tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) single crystal using a low temperature scanning tunneling microscope (STM) under ultrahigh-vacuum conditions, between 300 and 33 K with molecular resolution. All CDW...
Time-resolved Fermi surface mapping of the charge density wave material DyTe3
Wolf M.
2013-03-01
Full Text Available The femtosecond dynamics of the Fermi surface of DyTe3 and its band structure are investigated by time- and angle-resolved photoemission spectroscopy. We directly monitor the ultrafast collapse of the charge density wave gap within 200 fs.
Investigation of space charge in low-density polyethylene using a field probe technique
Khalil, M. Salah; Hansen, Bo Svarrer
1988-01-01
A test method that uses a capacitive field probe to investigate the space charge distribution in low-density polyethylene (LDPE) is described. Specimens of 7-mm thickness were stressed under 100 kV DC at room temperature and for different time periods. The results indicate that the LDPE insulation...
无
2000-01-01
Based on the density functional theory and the atom-bond electronegativity equalization model (ABEEM), a method is proposed to construct the softness matrix and to obtain the electron population normal modes (PNMs) for a closed system. Using this method the information about the bond charge polarization in a molecule can be obtained easily. The test calculation shows that the PNM obtained by this method includes all the modes about the bond charge polarization explicitly. And the bond charge polarization mode characterized by the biggest eigenvalue, which is the softest one of all modes related with chemical bonds, can describe the charge polarization process in a molecule as exquisitely as the corresponding ab initio method.
Blaise, G.; Pesty, F.; Garoche, P.
2009-02-01
Using a dedicated scanning electron microscope, operating in the spot mode, the charging properties of muscovite mica have been studied in the energy range of 100-8000 eV. The intrinsic yield curve σ0(E), representing the variation of the yield of the uncharged material with the energy E, has been established: the maximum value of the yield is 3.92 at E =300 eV and the two crossovers corresponding to σ0(E)=1 are, respectively, at energies EIexoemission (bursts of electrons) is produced at low energy when the net stored charge is positive. The interpretation of the current density effect on σ(D ) is based on the high rate of charging, the effect relative to negative charging is due to the expansion of the electron distribution, while the exoemission effect is due to the collective relaxation process of electrons.
Mokhtaria Drissi
2013-01-01
Full Text Available The molecular electron charge density distribution of the title compound is described accurately using the multipolar model of Hansen and Coppens. The net atomic charge and the in-crystal molecular dipole moment have been determined in order to understand the nature of inter- and intramolecular charge transfer. The study reveals the nature of intermolecular interactions including charge transfer and hydrogen bonds in the title compound. In this crystal, the molecules form dimers via N–HS intermolecular hydrogen bonds. The dimers are further linked by C–HO hydrogen bonds into chains along the c crystallographic axis. This study has also allowed us to determine the electrostatic potential and therefore locate the electropositive part and the electronegative part in molecular scale of the title compound.
Charge density wave crossover at low fillings in the fractional quantum Hall regime
We show that besides the Wigner Crystal, the lowest Landau level supports a state with the same crystalline symmetry but qualitatively different charge density distribution at low densities. Instead of periodic peaks the new state forms percolating ridges that may favor an energy decrease through correlated ring exchange contributions. For the case of half electron per cell a crossover is found close to filling 1/7 between this new state and the Wigner-like solid, showing that transitions may occur from one to the other as the electron density is varied. This result is consistent with recent experimental findings. (author)
The influence of oxidation on space charge formation in gamma-irradiated low-density polyethylene
Chen, G; Xie, H K; Banford, H M; Davies, A E
2003-01-01
The research presented in this paper investigates the role of oxidation in the formation of space charge in gamma-irradiated low-density polyethylene after being electrically stressed under dc voltage. Polyethylene plaques both with and without antioxidant were irradiated up to 500 kGy using a sup 6 sup 0 Co gamma source and space charge distributions were measured using the piezoelectric induced pressure wave propagation method. It has been found that a large amount of positive charge evolved adjacent to the cathode in the sample without antioxidant and was clearly associated with oxidation of the surface. The amount of charge formed for a given applied stress increased with the dose absorbed by the material. A model has been proposed to explain the formation of space charge and its profile. The charge decay after the removal of the external applied stress is dominated by a process being controlled by the cathode interfacial stress (charge injection) rather than a conventional RC circuit model. On the other ...
Transverse charge and magnetization densities in the nucleon's chiral periphery
Granados, Carlos G. [JLAB Newport News, VA (United States); Weiss, Christian [JLAB Newport News, VA (United States)
2014-01-01
In the light-front description of nucleon structure the electromagnetic form factors are expressed in terms of frame-independent transverse densities of charge and magnetization. Recent work has studied the transverse densities at peripheral distances b = O(M{pi}{sup -1}), where they are governed by universal chiral dynamics and can be computed in a model-independent manner. Of particular interest is the comparison of the peripheral charge and magnetization densities. We summarize (a) their interpretation as spin-independent and -dependent current matrix elements; (b) the leading-order chiral effective field theory results; (c) their mechanical interpretation in the light-front formulation; (d) the large-N_c limit of QCD and the role of {Delta} intermediate states; (e) the connection with generalized parton distributions and peripheral high-energy scattering processes.
Chemical bonding in view of electron charge density and kinetic energy density descriptors.
Jacobsen, Heiko
2009-05-01
Stalke's dilemma, stating that different chemical interpretations are obtained when one and the same density is interpreted either by means of natural bond orbital (NBO) and subsequent natural resonance theory (NRT) application or by the quantum theory of atoms in molecules (QTAIM), is reinvestigated. It is shown that within the framework of QTAIM, the question as to whether for a given molecule two atoms are bonded or not is only meaningful in the context of a well-defined reference geometry. The localized-orbital-locator (LOL) is applied to map out patterns in covalent bonding interaction, and produces results that are consistent for a variety of reference geometries. Furthermore, LOL interpretations are in accord with NBO/NRT, and assist in an interpretation in terms of covalent bonding. PMID:19090572
The utility of charge pumping to measure Si-SiO2 interface trap density in irradiated four-terminal VDMOSFETs is demonstrated. A modification of the conventional charge pumping approach is employed, where recombination of charge through interface traps in the neck region is measured in the drain. Three components of drain current resulting from the charge pumping measurement are identified. When the device is properly biased, charge pumping current can be separated from the other components of drain current and modeled over a wide range of interface trap densities using standard charge pumping theory. When sources of error are accounted for, radiation-induced interface trap densities measured with charge pumping are in good quantitative agreement with those estimated with the midgap charge separation and subthreshold hump techniques
The extended Peierls-Hubbard model is used to study the competition of the spin-density-wave (SDW) and charge-density-wave (CDW) states as well as the attendant localized excitations in quasi-one-dimensional systems like MX-chains. The ground state properties are first studied as a function of the Coulomb interaction U and the on-site electron-phonon coupling λ2. The SDW state dominates in the region of large U and small λ2, while the CDW state prevails in the opposite limit. In the intermediate region these two states compete with each other, one being stable, whereas the other being metastable. The localized excitations (polarons and excitons) are studied in detail in each region using the Bogoliubov-de Gennes formalism. The self-trapped excitons (STE) in the CDW dominating regime contain locally non-vanishing SDW distortions and vice versa. As λ2 increases, the number of bound states changes from two to four for the exciton case and from two to three for the polaron case. Upon its further increase, one type of STE with a certain pattern of SDW distortion and charge transfer is transforming into another type of STE with a different pattern. The possibilities of verifying the ground state properties in optical and transport experiments and identifying these local excitations in Raman and ENDOR measurements are discussed. (author). 25 refs, 11 figs
Crystal structure and charge density analysis of Li2NH by synchrotron X-ray diffraction
Complex hydrides, such as lithium amide (LiNH2) and lithium imide (Li2NH), have recently been noticed as one of the most promising materials for reversible hydrogen storage. In this paper, we reveal the bonding nature of hydrogen in Li2NH crystal by synchrotron powder X-ray diffraction measurement at room temperature. The crystal structure was refined by Rietveld method and the charge density distribution was analyzed by maximum entropy method (MEM). The Li2NH crystal is anti-fluorite type structure (space group Fm3-bar m) consisting of Li and NH. Hydrogen atom occupies randomly the 48h (Wyckoff notation) sites around N atom. The refined lattice constant is a=5.0742(2)A. The charge density distribution around NH anion in Li2NH is almost spherical. The number of electrons within the sphere around the Li and NH is estimated from the obtained charge density distribution. As the result, the ionic charge is expressed as [Li0.99+]2[NH]1.21-. Therefore, it is confirmed experimentally that Li2NH is ionically bonded
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...
Standard hydrogen electrode and potential of zero charge in density functional calculations
Tripkovic, Vladimir; Björketun, Mårten; Skúlason, Egill;
2011-01-01
Methods to explicitly account for half-cell electrode potentials have recently appeared within the framework of density functional theory. The potential of the electrode relative to the standard hydrogen electrode is typically determined by subtracting the experimental value of the absolute...... functional setups. By analyzing a dozen different water structures, built up from water hexamers, in their uncharged [potential of zero charge (PZC)] states on Pt(111), we then determine three different criteria (no net dipole, no charge transfer, and high water flexibility) that a water structure should...
Jung, Ju-Hyun; Yakhshiev, Ulugbek; Kim, Hyun-Chul
2016-03-01
We investigate the medium modification of the generalized vector form factors of the nucleon, which include the electromagnetic and energy-momentum tensor form factors, based on an in-medium modified π -ρ -ω soliton model. We find that the vector form factors of the nucleon in nuclear matter fall off faster than those in free space, which implies that the charge radii of the nucleon become larger in nuclear medium than in free space. We also compute the corresponding transverse charge densities of the nucleon in nuclear matter, which clearly reveal the increasing of the nucleon size in nuclear medium.
Jung, Ju-Hyun; Kim, Hyun-Chul
2015-01-01
We investigate the medium modification of the generalized vector form factors of the nucleon, which include the electromagnetic and energy-momentum tensor form factors, based on an in-medium modified $\\pi$-$\\rho$-$\\omega$ soliton model. We find that the vector form factors of the nucleon in nuclear matter fall off faster than those in free space, which implies that the charge radii of the nucleon become larger in nuclear medium than in free space. We also compute the corresponding transverse charge densities of the nucleon in nuclear matter, which clearly reveal the increasing of the nucleon size in nuclear medium.
Tian, Kai; Cao, Zhou; Xue, Yu-Xiong; Yang, Shi-Yu
2010-01-01
Heavy ions and pulsed lasers are important means to simulate the ionization damage effects on semiconductor materials. The analytic solution of high-energy heavy ion energy loss in silicon has been obtained using the Bethe-Bloch formula and the Kobetich-Katz theory, and some ionization damage parameters of Fe ions in silicon, such as the track structure and ionized charge density distribution, have been calculated and analyzed according to the theoretical calculation results. Using the Gaussian function and Beer's law, the parameters of the track structure and charge density distribution induced by a pulsed laser in silicon have also been calculated and compared with those of Fe ions in silicon, which provides a theoretical basis for ionization damage effect modeling.
Pushing X-ray charge densities to the limit: Comparative study of CoSb3
Schmøkel, Mette Stokkebro; Larsen, Finn Krebs; Overgaard, Jacob; Bjerg, Lasse; Cenedese, Simone; Jørgensen, Mads Ry Vogel; Christensen, Mogens; Iversen, Bo Brummerstedt
CoSb3 is a highly important host-guest material for the engineering of high-performance thermoelectric materials.[1] Its crystal structure has empty cavities and when guest atoms are added to CoSb3, its thermoelectric properties are greatly enhanced due to decreased thermal conductivity.[2] In...... order to understand the origin of the thermoelectric properties of this family of materials, it is important to understand the crystal structure and chemical bonding of the un-doped host material.[3] This can be achieved through analysis of the charge density, which in principle can be obtained from...... modeling of accurate X-ray diffraction data.[4] However, considering the heavy elements, the high symmetry and the perfect crystallinity of this inorganic network structure one cannot think of a much more challenging case for experimental charge density analysis. In the present study we analyze several low...
Exploring effective interactions through transition charge density study of 70,72,74,76Ge nuclei
A Shukla; P K Raina; P K Rath
2005-02-01
Transition charge densities (TCD) for $0^{+} → 2_{1}^{+}$ excitation have been calculated for 70, 72, 74, 76Ge nuclei within microscopic variational framework employing 23/2, 15/2, 21/2 and 19/2 valence space. The calculated TCDs for different monopole variants of Kuo interaction are compared with available experimental results. Other systematics like reduced transition probabilities (2) and static quadrupole moments (2) are also presented. It is observed that the transition density study acts as a sensitive probe for discriminating the response of different parts of effective interactions.
The malleability of uranium: manipulating the charge-density wave in epitaxial films
Springell, R.; Ward, R. C. C.; Bouchet, J.; Chivall, J.; Wermeille, D.; Normile, P. S.; Langridge, S.; Zochowski, S W; Lander, G. H.
2014-01-01
We report x-ray synchrotron experiments on epitaxial films of uranium, deposited on niobium and tungsten seed layers. Despite similar lattice parameters for these refractory metals, the uranium epitaxial arrangements are different and the strains propagated along the a-axis of the uranium layers are of opposite sign. At low temperatures these changes in epitaxy result in dramatic modifications to the behavior of the charge-density wave in uranium. The differences are explained with the curren...
Charge density wave in graphene: magnetic-field-induced Peierls instability
Fuchs, Jean-Noël; Lederer, Pascal
2006-01-01
We suggest that a magnetic-field-induced Peierls instability accounts for the recent experiment of Zhang et al. in which unexpected quantum Hall plateaus were observed at high magnetic fields in graphene on a substrate. This Peierls instability leads to an out-of-plane lattice distortion resulting in a charge density wave (CDW) on sublattices A and B of the graphene honeycomb lattice. We also discuss alternative microscopic scenarios proposed in the literature and leading to a similar CDW gro...
Charge density wave in graphene: magnetic-field-induced Peierls instability
Fuchs, Jean-Noël; Lederer, Pascal
2007-01-01
Proceeding of the "graphene conference" (25 September - 01 October 2006) held in Dresden. We suggest that a magnetic-field-induced Peierls instability accounts for the recent experiment of Zhang et al. in which unexpected quantum Hall plateaus were observed at high magnetic fields in graphene on a substrate. This Peierls instability leads to an out-of-plane lattice distortion resulting in a charge density wave (CDW) on sublattices A and B of the graphene honeycomb lattice. We also discuss ...
Astakhov, O.; Carius, R.; F. Finger; Petrusenko, Y.; Borysenko, V.; Barankov, D.
2009-01-01
The influence of dangling-bond defects and the position of the Fermi level on the charge carrier transport properties in undoped and phosphorous doped thin-film silicon with structure compositions all the way from highly crystalline to amorphous is investigated. The dangling-bond density is varied reproducibly over several orders of magnitude by electron bombardment and subsequent annealing. The defects are investigated by electron-spin-resonance and photoconductivity spectroscopies. Comparin...
Thermal ageing and its impact on charge trap density and breakdown strength in ldpe LDPE
Li, Ziyun; Chen, George; Fu, Mingli; Hou, Shuai
2015-01-01
Low-density polyethylene (LDPE) has been widely used as power cable insulation, because of its good electrical performance and stable chemical characteristics. However, in recent years, with the rise of large-capacity and long-distance HVDC transmission systems, the effect of space charge has a significant impact on the insulation selection and design. Furthermore, the change in the electrical performance of insulation after ageing is also required to be understood. It has been reported that ...
Infrared signature of the charge-density-wave gap in $ZrTe_3$
Perucchi, A.; Degiorgi, L.; Berger, H.
2005-01-01
The chain-like $ZrTe_3$ compound undergoes a charge-density-wave (CDW) transition at $T_{CDW}=63$ $K$, most strongly affecting the conductivity perpendicular to the chains. We measure the temperature ($T$) dependence of the optical reflectivity from the far infrared up to the ultraviolet with polarized light. The CDW gap $\\Delta(T)$ along the direction perpendicular to the chains is compatible for $T
Nuclear charge-exchange excitations in localized covariant density functional theory
The recent progress in the studies of nuclear charge-exchange excitations with localized covariant density functional theory is briefly presented, by taking the fine structure of spin-dipole excitations in 16O as an example. It is shown that the constraints introduced by the Fock terms of the relativistic Hartree-Fock scheme into the particle-hole residual interactions are straightforward and robust. (authors)
Effect of high magnetic fields on the charge density wave properties of KMo 6O 17
Rötger, A.; Dumas, J.; Marcus, J.; Schlenker, C.; Ulmet, J. P.; Audouard, A.; Askenazy, S.
1992-03-01
The electrical resistivity of the purple bronze KMo 6O 17 has been studied between 2 and 88 K with pulsed magnetic fields up to 35 T. Several anomalies are found on the curves Δρ/ρ(B) at different temperatures. The low field results are compared with previous measurements of susceptibility and magnetization. A phase diagram which may show a field displaced charge density wave instability and field induced transitions is proposed.
Nuclear charge-exchange excitations in localized covariant density functional theory
Liang, H Z; Nakatsukasa, T; Niu, Z M; Ring, P; Roca-Maza, X; Van Giai, N; Zhao, P W
2014-01-01
The recent progress in the studies of nuclear charge-exchange excitations with localized covariant density functional theory is briefly presented, by taking the fine structure of spin-dipole excitations in 16O as an example. It is shown that the constraints introduced by the Fock terms of the relativistic Hartree-Fock scheme into the particle-hole residual interactions are straightforward and robust.
Correlation of scanning-tunneling-microscope image profiles and charge-density-wave amplitudes
Scanning-tunneling-microscope (STM) studies of 4Hb-TaS2 and 4Hb-TaSe2 at 4.2 K show systematic correlation between the charge-density-wave (CDW) amplitude and the STM deflection. The 4Hb phases have both weak and strong CDW's in the trigonal prismatic and octahedral sandwiches, respectively. Scans on opposite faces of the same cleave allow a comparison of the STM response to the two types of CDW
In this paper we discuss representations of charge particle densities in particle-in-cell (PIC) simulations, analyze the sources and profiles of the intrinsic numerical noise, and present efficient methods for their removal. We devise two alternative estimation methods for charged particle distribution which represent significant improvement over the Monte Carlo cosine expansion used in the 2d code of Bassi, designed to simulate coherent synchrotron radiation (CSR) in charged particle beams. The improvement is achieved by employing an alternative beam density estimation to the Monte Carlo cosine expansion. The representation is first binned onto a finite grid, after which two grid-based methods are employed to approximate particle distributions: (i) truncated fast cosine transform (TFCT); and (ii) thresholded wavelet transform (TWT). We demonstrate that these alternative methods represent a staggering upgrade over the original Monte Carlo cosine expansion in terms of efficiency, while the TWT approximation also provides an appreciable improvement in accuracy. The improvement in accuracy comes from a judicious removal of the numerical noise enabled by the wavelet formulation. The TWT method is then integrated into Bassi's CSR code, and benchmarked against the original version. We show that the new density estimation method provides a superior performance in terms of efficiency and spatial resolution, thus enabling high-fidelity simulations of CSR effects, including microbunching instability.
Balsa Terzic, Gabriele Bassi
2011-07-01
In this paper we discuss representations of charge particle densities in particle-in-cell (PIC) simulations, analyze the sources and profiles of the intrinsic numerical noise, and present efficient methods for their removal. We devise two alternative estimation methods for charged particle distribution which represent significant improvement over the Monte Carlo cosine expansion used in the 2d code of Bassi, designed to simulate coherent synchrotron radiation (CSR) in charged particle beams. The improvement is achieved by employing an alternative beam density estimation to the Monte Carlo cosine expansion. The representation is first binned onto a finite grid, after which two grid-based methods are employed to approximate particle distributions: (i) truncated fast cosine transform (TFCT); and (ii) thresholded wavelet transform (TWT). We demonstrate that these alternative methods represent a staggering upgrade over the original Monte Carlo cosine expansion in terms of efficiency, while the TWT approximation also provides an appreciable improvement in accuracy. The improvement in accuracy comes from a judicious removal of the numerical noise enabled by the wavelet formulation. The TWT method is then integrated into Bassi's CSR code, and benchmarked against the original version. We show that the new density estimation method provides a superior performance in terms of efficiency and spatial resolution, thus enabling high-fidelity simulations of CSR effects, including microbunching instability.
Modelling of passive charge exchange emission and neutral background density deduction in JET
Passive Charge Exchange (PCX) emission induced by the interaction of neutral deuterium entering the plasma from the walls, and fully ionised light impurities in a tokamak fusion plasma have been investigated. The incentive was to improve the evaluation accuracy of active charge exchange (ACX) spectra, leading to ion temperature, impurity density and plasma rotation. The reconstruction of synthetic line-of-sight-integrated PCX emission spectra is based on a modelled neutral density profile as derived from the FRANTIC code, local emission rates for D0(1s) and D0(2s) donor states and finally local impurity ion densities (C6+, He2+) from CX analysis. As a result of the PCX modelling the experimental errors in ion temperature values can be reduced and the range of accessible PCX spectra extended from magnetic axis to separatrix. A comparison between the modelled intensity of the synthetic spectra and experimental PCX data allows also a consistency check of neutral density and its radial distribution. (author)
Fischer, Tobias
2016-01-01
In this article the role of the supersaturation density equation of state (EOS) is explored in simulations of failed core-collapse supernova explosions. Therefore the nuclear EOS is extended via a one-parameter excluded volume description for baryons, taking into account their finite and increasing volume with increasing density in excess of saturation density. Parameters are selected such that the resulting supernova EOS represent extreme cases, with high pressure variations at supersaturation density which feature extreme stiff and soft EOS variants of the reference case, i.e. without excluded volume corrections. Unlike in the interior of neutron stars with central densities in excess of several times saturation density, central densities of core-collapse supernovae reach only slightly above saturation density. Hence, the impact of the supersaturation density EOS on the supernova dynamics as well as the neutrino signal is found to be negligible. It is mainly determined from the low- and intermediate-density...
Overlap fermions, which preserve exact chiral symmetry on the lattice, provide a powerful tool for investigating the topological structure of the vacuum. Applying this formulation to zerotemperature quenched SU(3) configurations generated by means of the Luescher-Weisz action, we define the topological charge density with and without UV filtering and study its properties by looking at the density profile and the two-point correlation function. We observe that the density possesses global sign coherent structures, which get increasingly tangled as more and more modes are included. This change of the structure is also detected by the increasing negative tail of the two-point function. We also study the inverse participation ratio of the eigenmodes and discuss their dimensionality. (orig.)
Lagström, Tove; Gmür, Tobias A; Quaroni, Luca; Goel, Alok; Brown, Matthew A
2015-03-31
We show that attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy can be used to determine the surface charge density (SCD) of colloidal silica nanoparticles (NPs) in aqueous solution. We identify the Si-O stretch vibrations of neutral surface bound silanol, ≡Si-OH, and of the deprotonated group, ≡Si-O(-). The position of the Si-(OH) stretch vibration is shown to directly correlate with the NPs SCD as determined by traditional potentiometric titrations, shifting to lower wavenumber (cm(-1)) with increasing density of ≡Si-O(-). The origin of this shift is discussed in terms of inductive effects that reduce the ionic character of the Si-(OH) bond after delocalization of the negative charge left on a terminal ≡Si-O(-) group across the atoms within ∼1 nm of the charged site. Using this new methodology, we quantitatively determine the SCD of 9, 14, and 25 nm diameter colloidal silica in varying concentrations of NaCl electrolyte at different bulk pH. This novel spectroscopic approach to investigate SCDs provides several opportunities for in situ coupling, for example, in microfluidic channels or with liquid microjets, and requires only very little sample—all potential advantages over a traditional potentiometric titration. PMID:25761506
Long-range charge-density-wave proximity effect at cuprate/manganate interfaces
Frano, A.; Blanco-Canosa, S.; Schierle, E.; Lu, Y.; Wu, M.; Bluschke, M.; Minola, M.; Christiani, G.; Habermeier, H. U.; Logvenov, G.; Wang, Y.; van Aken, P. A.; Benckiser, E.; Weschke, E.; Le Tacon, M.; Keimer, B.
2016-08-01
The interplay between charge density waves (CDWs) and high-temperature superconductivity is currently under intense investigation. Experimental research on this issue is difficult because CDW formation in bulk copper oxides is strongly influenced by random disorder, and a long-range-ordered CDW state in high magnetic fields is difficult to access with spectroscopic and diffraction probes. Here we use resonant X-ray scattering in zero magnetic field to show that interfaces with the metallic ferromagnet La2/3Ca1/3MnO3 greatly enhance CDW formation in the optimally doped high-temperature superconductor YBa2Cu3O6+δ (δ ~ 1), and that this effect persists over several tens of nanometres. The wavevector of the incommensurate CDW serves as an internal calibration standard of the charge carrier concentration, which allows us to rule out any significant influence of oxygen non-stoichiometry, and to attribute the observed phenomenon to a genuine electronic proximity effect. Long-range proximity effects induced by heterointerfaces thus offer a powerful method to stabilize the charge-density-wave state in the cuprates and, more generally, to manipulate the interplay between different collective phenomena in metal oxides.
Growth dynamics, charge density, and structure of polyamide thin-film composite membranes
Matthews, Tamlin
The main objectives of this dissertation are to characterize polyamide layers formed on polysulfone supports, without physical or chemical removal, so that it is close to its native form, which has been used in industrial reverse osmosis applications. Growth dynamics by diffuse reflectance spectroscopy was developed for the polymerization of polyamide on porous polysulfone supports using varying concentrations of m-phenylenediamine (MPD) in water of 0.1-- 100 g/L with a fixed concentration of trimesoyl chloride (TMC) in hexane of 1 g/L, and varying TMC concentrations of 0.1--10 g/L with a fixed MPD concentration of 20 g/L. A relationship was developed between diffuse reflectance and polyamide thickness. The diffuse reflectance data shows that ~50% of the polyamide thickness is produced in 2 g/L. All studied concentrations of TMC at a fixed 20 g/L MPD concentration produced a polyamide thickness of ≈120 nm. Polyamide thickness increases from ≈10 to 110 nm with increasing concentration of MPD at 1 g/L TMC. The roughness measured with AFM increases with increasing MPD concentration but decreases with increasing TMC concentration. At MPD concentrations polyamide does not grow on top of the polysulfone. The charge density of polyamide layers arises from unpolymerized free amine and carboxylic groups contributing positive and negative charges, respectively. The negative charge groups from carboxylic acid were tagged with Ag+. Using the same concentration ranges as the growth dynamics study, the charge densities were characterized in the bulk by RBS and in the near-surface by XPS. With increasing concentration of MPD, the charge density in the near-surface region is constant and ≈0.3 M, due to constant surface contact with the carboxylic acid containing TMC monomer. The charge density decreases from 0.3 M to 0.1 M in the polyamide bulk with increasing MPD concentration. TMC showed a 30x increase in charge density from 0.02 to 0.61 g/L in the bulk polyamide between 0
Changes in Surface Charge Density of Blood Cells in Fatal Accidental Hypothermia.
Szeremeta, Michał; Petelska, Aneta Dorota; Kotyńska, Joanna; Pepiński, Witold; Naumowicz, Monika; Figaszewski, Zbigniew Artur; Niemcunowicz-Janica, Anna
2015-12-01
The objective of this research was to evaluate postmortem changes concerning electric charge of human erythrocytes and thrombocytes in fatal accidental hypothermia. The surface charge density values were determined on the basis of the electrophoretic mobility measurements of the cells conducted at various pH values of electrolyte solution. The surface charge of erythrocyte membranes after fatal accidental hypothermia increased compared to the control group within whole range of experimental pH values. Moreover, a slight shift of the isoelectric point of erythrocyte membranes towards high pH values was observed. The surface charge of thrombocyte membranes in fatal accidental hypothermia decreased at low pH compared to the control group. However, at pH range 4-9, the values increased compared to the control group. The isoelectric point of thrombocyte membranes after fatal accidental hypothermia was slightly shifted towards low pH values compared to the control group. The observed changes are probably connected with the partial destruction and functional changes of the blood cell structure. PMID:26364031
Li, Hao; Chen, Guang; Sinha, Shayandev; Das, Siddhartha; Soft Matter, Interfaces,; Energy Laboratory (Smiel) Team
Understanding the electric double layer (EDL) electrostatics of spherical polyelectrolyte (PE) brushes, which are spherical particles grafted with PE layers, is essential for appropriate use of PE-grfated micro-nanoparticles for targeted drug delivery, oil recovery, water harvesting, emulsion stabilization, emulsion breaking, etc. Here we elucidate the EDL electrostatics of spherical PE brushes for the case where the PE exhibits pH-dependent charge density. This pH-dependence necessitates the consideration of explicit hydrogen ion concentration, which in turn dictates the distribution of monomers along the length of the grafted PE. This monomer distribution is shown to be a function of the nature of the sphere (metallic or a charged or uncharged dielectric or a liquid-filled sphere). All the calculations are performed for the case where the PE electrostatics can be decoupled from the PE elastic and excluded volume effects. Initial predictions are also provided for the case where such decoupling is not possible.
George, S.C.; Lisk, M.; Quezada, R.A. [CSIRO Div. of Petroleum Resources, North Ryde (Australia); Summons, R.E. [Australian Geological Survey Organisation, Canberra (Australia)
1998-12-31
The South Pepper oilfield, located in the Barrow Sub-basin on the NW margin of the Australian continent, has experienced a multi-phase charge history. Abundant oil-bearing fluid inclusions are present in samples from within the current gas cap, suggesting that an oil column existed prior to gas. This palaeo-oil (gas-leg FI oil) has Ts/Tm and C{sub 29}/C{sub 30} {alpha}{beta} hopane ratios of {approx} 1 and the C{sub 35} homohopanes are a significant proportion of the extended homohopanes. It has lower Pr/Ph and diasterane/sterane ratios than the currently reservoired live oil and contains gammacerane, a series of peaks tentatively identified as C{sub 30} to C{sub 34} 17{alpha}(H)-30-norhopanes and a large amount of 2{alpha}-methylhopanes. Collectively, geochemical analysis of the gas-leg FI oil suggests that it was generated from a less mature, more calcareous rock, deposited under more reducing conditions than the Upper Jurassic Dingo Claystone, the main source of the live oil. In addition the presence of C{sub 30} dinosteranes in the gas-leg FI oil provides a Triassic or younger age constraint. This makes Palaeozoic carbonates an unlikely source. Possible source intervals for the gas-leg FI oil are thin, Lower Jurassic limestones and marls which occur at the base of the Lower Dingo Claystone, or a thin limestone unit (the Cunaloo Member) at the base of the Triassic Locker Shale. Samples from within the present oil-leg also contain abundant oil inclusions, consistent with high oil saturations at the present day. However, these oil inclusions exhibit different fluorescent colours, suggesting they represent a second oil charge. Complex charge histories are common and the analysis of palaeo-oils trapped within fluid inclusions provides the opportunity to achieve a more comprehensive assessment of hydrocarbon charge. (author)
Space Charge Neutralization of DEMO Relevant Negative Ion Beams at Low Gas Density
The application of neutral beams to future power plant devices (DEMO) is dependent on achieving significantly improved electrical efficiency and the most promising route to achieving this is by implementing a photoneutralizer in place of the traditional gas neutralizer. A corollary of this innovation would be a significant reduction in the background gas density through which the beam is transported between the accelerator and the neutralizer. This background gas is responsible for the space charge neutralization of the beam, enabling distances of several metres to be traversed without significant beam expansion. This work investigates the sensitivity of a D- beam to reduced levels of space charge compensation for energies from 100 keV to 1.5 MeV, representative of a scaled prototype experiment, commissioning and full energy operation. A beam transport code, following the evolution of the phase space ellipse, is employed to investigate the effect of space charge on the beam optics. This shows that the higher energy beams are insensitive to large degrees of under compensation, unlike the lower energies. The probable degree of compensation at low gas density is then investigated through a simple, two component beam-plasma model that allows the potential to be negative. The degree of under-compensation is dependent on the positive plasma ion energy, one source of which is dissociation of the gas by the beam. The subsequent space charge state of the beam is shown to depend upon the relative times for equilibration of the dissociation energy and ionization by the beam ions.
Terzić, Balša; Bassi, Gabriele
2011-07-01
In this paper we discuss representations of charge particle densities in particle-in-cell simulations, analyze the sources and profiles of the intrinsic numerical noise, and present efficient methods for their removal. We devise two alternative estimation methods for charged particle distribution which represent significant improvement over the Monte Carlo cosine expansion used in the 2D code of Bassi et al. [G. Bassi, J. A. Ellison, K. Heinemann, and R. Warnock, Phys. Rev. ST Accel. Beams 12, 080704 (2009); PRABFM1098-440210.1103/PhysRevSTAB.12.080704G. Bassi and B. Terzić, in Proceedings of the 23rd Particle Accelerator Conference, Vancouver, Canada, 2009 (IEEE, Piscataway, NJ, 2009), TH5PFP043], designed to simulate coherent synchrotron radiation (CSR) in charged particle beams. The improvement is achieved by employing an alternative beam density estimation to the Monte Carlo cosine expansion. The representation is first binned onto a finite grid, after which two grid-based methods are employed to approximate particle distributions: (i) truncated fast cosine transform; and (ii) thresholded wavelet transform (TWT). We demonstrate that these alternative methods represent a staggering upgrade over the original Monte Carlo cosine expansion in terms of efficiency, while the TWT approximation also provides an appreciable improvement in accuracy. The improvement in accuracy comes from a judicious removal of the numerical noise enabled by the wavelet formulation. The TWT method is then integrated into the CSR code [G. Bassi, J. A. Ellison, K. Heinemann, and R. Warnock, Phys. Rev. ST Accel. Beams 12, 080704 (2009)PRABFM1098-440210.1103/PhysRevSTAB.12.080704], and benchmarked against the original version. We show that the new density estimation method provides a superior performance in terms of efficiency and spatial resolution, thus enabling high-fidelity simulations of CSR effects, including microbunching instability.
In this paper we discuss representations of charge particle densities in particle-in-cell simulations, analyze the sources and profiles of the intrinsic numerical noise, and present efficient methods for their removal. We devise two alternative estimation methods for charged particle distribution which represent significant improvement over the Monte Carlo cosine expansion used in the 2D code of Bassi et al. (G. Bassi, J.A. Ellison, K. Heinemann and R. Warnock Phys. Rev. ST Accel. Beams 12 080704 (2009)G. Bassi and B. Terzic, in Proceedings of the 23rd Particle Accelerator Conference, Vancouver, Canada, 2009 (IEEE, Piscataway, NJ, 2009), TH5PFP043), designed to simulate coherent synchrotron radiation (CSR) in charged particle beams. The improvement is achieved by employing an alternative beam density estimation to the Monte Carlo cosine expansion. The representation is first binned onto a finite grid, after which two grid-based methods are employed to approximate particle distributions: (i) truncated fast cosine transform; and (ii) thresholded wavelet transform (TWT). We demonstrate that these alternative methods represent a staggering upgrade over the original Monte Carlo cosine expansion in terms of efficiency, while the TWT approximation also provides an appreciable improvement in accuracy. The improvement in accuracy comes from a judicious removal of the numerical noise enabled by the wavelet formulation. The TWT method is then integrated into the CSR code (G. Bassi, J.A. Ellison, K. Heinemann and R. Warnock Phys. Rev. ST Accel. Beams 12 080704 (2009)), and benchmarked against the original version. We show that the new density estimation method provides a superior performance in terms of efficiency and spatial resolution, thus enabling high-fidelity simulations of CSR effects, including microbunching instability.
Calculation of the Nuclear Transition Charge Density in a Microscopic sdgIBM-1
ZHANG Zhan-Jun; SANG Jian-ping; LIU Yong
2000-01-01
Formulae of proton and neutron boson structure functions (BSF's) are deduced in terms of a microscopic approach of sdgIBM (namely, microscopic sdgIBM). For the nucleus 190Os, the value of BSF's is worked out. Due to the high similarity, the maximum F-spin truncation is made under the full-symmetry approximation. Thereafter, calculations of E2 and E4 transition charge densities (TCD's) are performed in the sdgIBM-1. It is found that the E2 and E4 TCD's can be reproduced quite satisfactorily in the uniform frame of microscopic sdgIBM-1.
Charge-density-wave phase slip in NbSe3
We have studied the phase-slip process by which charge-density-wave (CDW) current is converted to single-particle current at electrical contacts. Transport and X-ray scattering measurements indicate that an excess voltage Vps dropped between current contacts induces a large static deformation of the CDW phase. The measured Vps- and temperature-dependent phase-slip rates are consistent with a model in which CDW dislocation loops are thermally nucleated in the presence of these deformations. The effects of impurities and contact perturbations on the phase slip process are also discussed. (orig.)
Instability and Charge Density Wave of Metallic Quantum Chains on a Silicon Surface
Yeom, H.W. [Research Center for Spectrochemistry, the University of Tokyo, Tokyo 113-0033 (Japan); Takeda, S.; Horikoshi, K.; Nagao, T.; Hasegawa, S. [Department of Physics, the University of Tokyo, Tokyo 113-0033 (Japan); Rotenberg, E.; Lee, C.M. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Matsuda, I.; Ohta, T. [Department of Chemistry, the University of Tokyo, Tokyo 113-0033 (Japan); Schaefer, J.; Kevan, S.D. [Department of Physics, University of Oregon, Eugene, Oregon 97403 (United States); Nagao, T.; Hasegawa, S. [CREST, the Japan Science and Technology Corporation, Saitama 332-0012 (Japan)
1999-06-01
Self-assembled indium linear chains on the Si(111) surface are found to exhibit instability of the metallic phase and 1D charge density wave (CDW). The room-temperature metallic phase of these chains undergoes a temperature-induced, reversible transition into a semiconducting phase. The 1D CDW along the chains is observed directly in real space by scanning tunneling microscopy at low temperature. The Fermi contours of the metallic phase measured by angle-resolved photoemission exhibit a perfect nesting predicting precisely the CDW periodicity. {copyright} {ital 1999} {ital The American Physical Society }
Instability and Charge Density Wave of Metallic Quantum Chains on a Silicon Surface
Self-assembled indium linear chains on the Si(111) surface are found to exhibit instability of the metallic phase and 1D charge density wave (CDW). The room-temperature metallic phase of these chains undergoes a temperature-induced, reversible transition into a semiconducting phase. The 1D CDW along the chains is observed directly in real space by scanning tunneling microscopy at low temperature. The Fermi contours of the metallic phase measured by angle-resolved photoemission exhibit a perfect nesting predicting precisely the CDW periodicity. copyright 1999 The American Physical Society
Distance-of-flight spectra of charge density of ions generated with a low laser intensity
Krása, Josef; Velardi, L.; Lorusso, A.; Delle Side, D.; Nassisi, V.
Vol. 508. Bristol : IOP Publishing, 2014, "012004-1"-"012004-5". ISSN 1742-6588. [Plasma Physics by Laser and Applications 2013 Conference (PPLA2013). Lecce (IT), 02.10.2013-04.10.2013] R&D Projects: GA MŠk EE2.3.20.0279; GA ČR GAP205/12/0454 Grant ostatní: LaserZdroj (OP VK 3)(XE) CZ.1.07/2.3.00/20.0279 Institutional support: RVO:68378271 Keywords : laser ion sources * map of ion charge density * ion expansion * modeling Subject RIV: BL - Plasma and Gas Discharge Physics
Instanton Aharonov-Bohm effect and macroscopic quantum coherence in charge-density-wave systems
It is predicted that in a charge-density-wave (CDW) ring-shaped conductor, placed in an external vector-potential field, there should appear a new Aharonov-Bohm contribution to the magnetic susceptibility and the electrical conductivity oscillating as a function of the flux with the period φ0=hc/2e. This contribution arises from instanton transitions between degenerate vacua of the CDW-condensate and is the solid-state realization of θ-vacuum in the quantum field theory. The period transforms into φ0/N in N strongly correlated parallel CDW chains. (author). 27 refs, 2 figs
Time-of-flight spectra for mapping of charge density of ionsproduced by laser
Krása, Josef; Parys, P.; Velardy, L.; Velyhan, Andriy; Ryc, L.; Delle Side, D.; Nassisi, V.
2014-01-01
Roč. 32, č. 1 (2014), s. 15-20. ISSN 0263-0346 R&D Projects: GA MŠk EE2.3.20.0279; GA ČR GAP205/12/0454 Grant ostatní: Laser Zdroj (OP VK 3)(XE) CZ.1.07/2.3.00/20.0279 Institutional support: RVO:68378271 Keywords : laser ion sources * map of ion charge density * ion expansion * modeling Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.295, year: 2014
Pressure dependence of the charge-density-wave gap in rare-earth tritellurides.
Sacchetti, A; Arcangeletti, E; Perucchi, A; Baldassarre, L; Postorino, P; Lupi, S; Ru, N; Fisher, I R; Degiorgi, L
2007-01-12
We investigate the pressure dependence of the optical properties of CeTe3, which exhibits an incommensurate charge-density-wave (CDW) state already at 300 K. Our data are collected in the midinfrared spectral range at room temperature and at pressures between 0 and 9 GPa. The energy for the single particle excitation across the CDW gap decreases upon increasing the applied pressure, similarly to the chemical pressure by rare-earth substitution. The broadening of the bands upon lattice compression removes the perfect nesting condition of the Fermi surface and therefore diminishes the impact of the CDW transition on the electronic properties of RTe3. PMID:17358625
Pressure Dependence of the Charge-Density-Wave Gap in Rare-Earth Tri-Tellurides
Sacchetti, A.; /Zurich, ETH; Arcangeletti, E.; Perucchi, A.; Baldassarre, L.; Postorino, P.; Lupi, S.; /Rome U.; Ru, N.; Fisher, I.R.; /Stanford U., Geballe Lab.; Degiorgi, L.; /Zurich, ETH
2009-12-14
We investigate the pressure dependence of the optical properties of CeTe{sub 3}, which exhibits an incommensurate charge-density-wave (CDW) state already at 300 K. Our data are collected in the mid-infrared spectral range at room temperature and at pressures between 0 and 9 GPa. The energy for the single particle excitation across the CDW gap decreases upon increasing the applied pressure, similarly to the chemical pressure by rare-earth substitution. The broadening of the bands upon lattice compression removes the perfect nesting condition of the Fermi surface and therefore diminishes the impact of the CDW transition on the electronic properties of RTe{sub 3}.
Pressure dependence of the charge-density-wave gap in rare-earth tri-tellurides
A. Sacchetti; Arcangeletti, E.; Perucchi, A.; Baldassarre, L.; Postorino, P.; Lupi, S.; Ru, N.; Fisher, I. R.; Degiorgi, L.
2006-01-01
We investigate the pressure dependence of the optical properties of CeTe$_3$, which exhibits an incommensurate charge-density-wave (CDW) state already at 300 K. Our data are collected in the mid-infrared spectral range at room temperature and at pressures between 0 and 9 GPa. The energy for the single particle excitation across the CDW gap decreases upon increasing the applied pressure, similarly to the chemical pressure by rare-earth substitution. The broadening of the bands upon lattice com...
Optical properties of the Ce and La ditelluride charge density wave compounds
Lavagnini, M.; Sacchetti, A.; Degiorgi, L.; /Zurich, ETH; Shin, K.Y.; Fisher, I.R.; /Stanford U., Geballe Lab. /Stanford U., Appl. Phys. Dept.
2010-02-15
The La and Ce di-tellurides LaTe{sub 2} and CeTe{sub 2} are deep in the charge-density-wave (CDW) ground state even at 300 K. We have collected their electrodynamic response over a broad spectral range from the far infrared up to the ultraviolet. We establish the energy scale of the single particle excitation across the CDW gap. Moreover, we find that the CDW collective state gaps a very large portion of the Fermi surface. Similarly to the related rare earth tri-tellurides, we envisage that interactions and Umklapp processes play a role in the onset of the CDW broken symmetry ground state.
Nucleon to $\\Delta$ transition form factors and empirical transverse charge densities
Chakrabarti, Dipankar
2016-01-01
We investigate the nucleon to $\\Delta$ transition form factors in a soft-wall AdS/QCD model and a light-front quark-diquark model inspired by AdS/QCD. From the transition form factors we evaluate the transition charge densities which influences the nucleon to $\\Delta$ excitation. Here we consider both the unpolarized and the transversely polarized cases. The AdS/QCD predictions are compared with available experimental data and with the results of the global parameterization, MAID2007.
Calculation of the nuclear transition charge density in a microscopic adgIBM-1
Formulae of proton and neutron boson structure functions (BFS's) are deduced in terms of a microscopic approach of sdgIBM (namely, microscopic sdgIBM). For the nucleus 190Os, the value of BSF's is worked out. Due to the high similarity, the maximum F-spin truncation is made under the full-symmetry approximation. Thereafter, calculations of E2 and E4 transition charge densities (TCD's) are performed in the sdgIBM-1. It is found that the E2 and E4 TCD's can be reproduced quite satisfactorily in the uniform frame of microscopic sdgIBM-1
Scanning tunneling microscopy of charge-density waves in NbSe3
The charge-density wave (CDW) structure in NbSe3 due to the two independent CDW's has been imaged by scanning microscopy. As predicted by band-structure considerations, the CDW modulation is observed to be substantially localized on different chains for the separate CDW's. AT 77 K where only the high-temperature CDW exists, a relatively weak modulation with a single component along the b axis is observed. At 4.2 K the low-temperature CDW contributes a much stronger ∼4b0 x 2c0 superlattice modulation
Origin of the charge density wave in 1T-TiSe2
Zhu, Zhiyong
2012-06-27
All-electron ab initio calculations are used to study the microscopic origin of the charge density wave (CDW) in 1T-TiSe2. A purely electronic picture is ruled out as a possible scenario, indicating that the CDW transition in the present system is merely a structural phase transition. The CDW instability is the result of a symmetry lowering by electron correlations occurring with electron localization. Suppression of the CDW in pressurized and in Cu-intercalated 1T-TiSe2 is explained by a delocalization of the electrons, which weakens the correlations and counteracts the symmetry lowering.
Regnier, D.; Dubray, N.; Schunck, N.; Verrière, M.
2016-05-01
Background: Accurate knowledge of fission fragment yields is an essential ingredient of numerous applications ranging from the formation of elements in the r process to fuel cycle optimization for nuclear energy. The need for a predictive theory applicable where no data are available, together with the variety of potential applications, is an incentive to develop a fully microscopic approach to fission dynamics. Purpose: In this work, we calculate the pre-neutron emission charge and mass distributions of the fission fragments formed in the neutron-induced fission of 239Pu using a microscopic method based on nuclear density functional theory (DFT). Methods: Our theoretical framework is the nuclear energy density functional (EDF) method, where large-amplitude collective motion is treated adiabatically by using the time-dependent generator coordinate method (TDGCM) under the Gaussian overlap approximation (GOA). In practice, the TDGCM is implemented in two steps. First, a series of constrained EDF calculations map the configuration and potential-energy landscape of the fissioning system for a small set of collective variables (in this work, the axial quadrupole and octupole moments of the nucleus). Then, nuclear dynamics is modeled by propagating a collective wave packet on the potential-energy surface. Fission fragment distributions are extracted from the flux of the collective wave packet through the scission line. Results: We find that the main characteristics of the fission charge and mass distributions can be well reproduced by existing energy functionals even in two-dimensional collective spaces. Theory and experiment agree typically within two mass units for the position of the asymmetric peak. As expected, calculations are sensitive to the structure of the initial state and the prescription for the collective inertia. We emphasize that results are also sensitive to the continuity of the collective landscape near scission. Conclusions: Our analysis confirms
Fischer, Tobias [University of Wroclaw, Wroclaw (Poland)
2016-03-15
In this article the role of the supersaturation density equation of state (EOS) is explored in simulations of failed core-collapse supernova explosions. Therefore the nuclear EOS is extended via a one-parameter excluded-volume description for baryons, taking into account their finite and increasing volume with increasing density in excess of saturation density. Parameters are selected such that the resulting supernova EOS represent extreme cases, with high pressure variations at supersaturation density which feature extreme stiff and soft EOS variants of the reference case, i.e. without excluded-volume corrections. Unlike in the interior of neutron stars with central densities in excess of several times saturation density, central densities of core-collapse supernovae reach only slightly above saturation density. Hence, the impact of the supersaturation density EOS on the supernova dynamics as well as the neutrino signal is found to be negligible. It is mainly determined from the low- and intermediate-density domain, which is left unmodified within this generalized excluded volume approach. (orig.)
Fischer, Tobias
2016-03-01
In this article the role of the supersaturation density equation of state (EOS) is explored in simulations of failed core-collapse supernova explosions. Therefore the nuclear EOS is extended via a one-parameter excluded-volume description for baryons, taking into account their finite and increasing volume with increasing density in excess of saturation density. Parameters are selected such that the resulting supernova EOS represent extreme cases, with high pressure variations at supersaturation density which feature extreme stiff and soft EOS variants of the reference case, i.e. without excluded-volume corrections. Unlike in the interior of neutron stars with central densities in excess of several times saturation density, central densities of core-collapse supernovae reach only slightly above saturation density. Hence, the impact of the supersaturation density EOS on the supernova dynamics as well as the neutrino signal is found to be negligible. It is mainly determined from the low- and intermediate-density domain, which is left unmodified within this generalized excluded volume approach.
Electronic properties and charge density of BeZn1−Te alloys
C B Swarnkar; U Paliwal; N N Patel; K B Joshi
2011-06-01
Electronic band structure calculations are performed for the BeZn1−Te (0 ≤ ≤ 1 in steps of 0.2) alloys following the empirical pseudopotential method. The alloying effects are modelled through the modified virtual crystal approximation. Throughout the composition, valence band maximum resides at the point. The conduction band minimum, however, shifts from to point of symmetry when = 0.27. The observed crossover from direct to indirect bandgap is well in accordance with the experimental observations. Effect of alloying on the density of states is also discussed. The charge density distribution along a few major planes is computed and discussed. The electronic band structure related parameters like bandwidths, bandgaps and ionicity are reported and compared with experimental data wherever available. We also give estimates of cohesive energy and bulk modulus for the alloys.
Harris, Alexander R; Molino, Paul J; Kapsa, Robert M I; Clark, Graeme M; Paolini, Antonio G; Wallace, Gordon G
2015-01-01
Neural stimulation is used in the cochlear implant, bionic eye, and deep brain stimulation, which involves implantation of an array of electrodes into a patient's brain. The current passed through the electrodes is used to provide sensory queues or reduce symptoms associated with movement disorders and increasingly for psychological and pain therapies. Poor control of electrode properties can lead to suboptimal performance; however, there are currently no standard methods to assess them, including the electrode area and charge density. Here we demonstrate optical and electrochemical methods for measuring these electrode properties and show the charge density is dependent on electrode geometry. This technique highlights that materials can have widely different charge densities but also large variation in performance. Measurement of charge density from an electroactive area may result in new materials and electrode geometries that improve patient outcomes and reduce side effects. PMID:25495574
Carnal, Fabrice; Stoll, Serge
2011-01-01
Complex formation between a weak flexible polyelectrolyte chain and one positively charged nanoparticle in presence of explicit counterions and salt particles is investigated using Monte Carlo simulations. The influence of parameters such as the nanoparticle surface charge density, salt valency, and solution property such as the pH on the chain protonation/deprotonation process and monomer adsorption at the nanoparticle surface are systematically investigated. It is shown that the nanoparticl...
Topology density correlator on dynamical domain-wall ensembles with nearly frozen topological charge
Fukaya, H; Cossu, G; Hashimoto, S; Kaneko, T; Noaki, J
2014-01-01
Global topological charge decorrelates very slowly or even freezes in fine lattice simulations. On the other hand, its local fluctuations are expected to survive and lead to the correct physical results as long as the volume is large enough. We investigate this issue on recently generated configurations including dynamical domain-wall fermions at lattice spacings a = 0.08 fm and finer. We utilize the Yang-Mills gradient flow to define the topological charge density operator and calculate its long-distance correlation, through which we propose a new method for extracting the topological susceptibility in a sub-volume. This method takes care of the finite volume correction, which reduces the bias caused by the global topological charge. Our lattice data clearly show a shorter auto-correlation time than that of the naive definition using the whole lattice, and are less sensitive to the global topological history. Numerical results show a clear sea-quark mass dependence, which agrees well with the prediction of c...
Density functional theory for the description of charge-transfer processes at TTF/TCNQ interfaces
Van Regemorter, Tanguy
2012-09-15
In the field of organic electronics, a central issue is to assess how the frontier electronic levels of two adjacent organic layers align with respect to one another at the interface. This alignment can be driven by the presence of a partial charge transfer and the formation of an interface dipole; it plays a key role for instance in determining the rates of exciton dissociation or exciton formation in organic solar cells or light-emitting diodes, respectively. Reliably modeling the processes taking place at these interfaces remains a challenge for the computational chemistry community. Here, we review our recent theoretical work on the influence of the choice of density functional theory (DFT) methodology on the description of the charge-transfer character in the ground state of TTF/ TCNQ model complexes and interfaces. Starting with the electronic properties of the isolated TTF and TCNQ molecules and then considering the charge transfer and resulting interface dipole in TTF/TCNQ donor-acceptor stacks and bilayers, we examine the impact of the choice of DFT functional in describing the interfacial electronic structure. Finally, we employ computations based on periodic boundary conditions to highlight the impact of depolarization effects on the interfacial dipole moment. © Springer-Verlag 2012.
Space Charge Trapping and Conduction in Low-Density Polyethylene/Silica Nanocomposite
Wu; Jiandong; Yin; Yi; Lan; Li; Wang; Qiaohua; Li; Xuguang; Xiao; Dengming
2012-04-01
The high field conduction and space charge distribution were investigated in low-density polyethylene (LDPE) and LDPE/silica nanocomposites filled with various concentrations of nanosilica. The results indicate that nanosilica could effectively suppress space charge accumulation at nanofiller concentrations from 0.1 to 5.0 wt %. However, the conduction current at a high field significantly increases at low concentrations from 0.1 to 0.5 wt % and remarkably reduces at high concentrations from 0.5 to 5.0 wt %. It is shown that the trap depth corresponding to the time from 2 to 3600 s significantly decreases at low nanofiller concentrations from 0.1 to 0.5 wt %. However, the depth of deep traps corresponding to the time from 100 to 3600 s increases with the increase in nanofiller concentration from 0.5 to 5.0 wt %. Moreover, the depth of shallow traps corresponding to the time from 2 to 100 s increases at concentrations from 0.5 to 2.0 wt %, and then it decreases at concentrations from 2.0 to 5.0 wt %. In addition, the apparent mobility varies with the modification of trap depth caused by the introduction of nanofiller. The threshold field EΩ-t for remarkable charge injection and Et-c proportional to the total trap density H are significantly lower in the nanocomposite with a low nanosilica concentration, i.e., 0.1 and 0.5 wt %, while both of them increase at concentrations from 0.5 to 5.0 wt %. It is considered that the impurity effect is greater than the nanofiller effect at a low nanofiller concentration. The deep trap is speculated as the chemical trap in the interface of the nanofiller bonding strongly with the polymer chain, while the shallow trap may be related to the chemical trap in the weakly bonded interface. It is clear that the space charge behavior and conduction are significantly affected by modification of the trap depth and density distribution owing to the introduction of nanofiller.
Charge and spin density in s-stable rare earth intermetallic compounds
This thesis deals with a study of the electronic structure of rare earth intermetallic compounds, in particular the electronic charge and spin density distribution. These are closely related to the properties of the rare earth ions, which carry the partly filled 4f shell. In chapter 1 a survey of the theory of hyperfine interaction as far as it has a bearing on the Moessbauer effect of 155Gd and 151Eu is given. Also some details of the Moessbauer spectra, which have practical importance are discussed. In chapter 2 the experimental set-up is described. Special attention is paid to the gamma radiation source and gamma detection requirements. In chapter 3 the author introduces the theoretical framework which will be used to interpret the measurements. In chapter 4 the results of the 155Gd Moessbauer measurements are presented. Also it is discussed how the result can be understood in terms of the charge and spin density in rare earth intermetallic compounds. In order to lend support to the picture emerging from the previous chapter, in chapter 5 the conduction electron band structure of some representative Gd intermetallics is computed with an approximate semi-empirical LCAO method. The results are compared with those from chapter 4. Finally, in chapter 6, the 151Eu resonance is used to investigate the temperature dependence of the hyperfine field and line width in the Eu intermetallic compounds Eu2Mg17 and EuMg5. (Auth.)
Computational analysis of the influence of initial fixed charge density on pH-sensitive hydrogels
In this paper, we conduct a computational analysis of the effects of initial fixed charge density on the responsive performance of pH-sensitive hydrogels to environmental change in solution pH. The analysis is based on a chemo-electro-mechanical formulation previously termed the multi-effect-coupling pH-stimulus (MECpH) model. In this work, we improve the MECpH model by incorporating the finite deformation formulation into the mechanical equilibrium equation. The present model consisting of coupled nonlinear partial differential equations is solved via a meshless numerical technique called the Hermite-cloud method with the modified Newton iteration methodology. After validation of the MECpH model by comparing the computational results with experimental data available in the literature, several computational case studies are carried out for analysis of the effects of initial fixed charge density on the distributive variations of the diffusive ion concentrations and electric potential and on the deformation of the pH-stimulus-responsive hydrogels, when they are immersed in different buffered solutions
Yu-ling Chu; Zhong Yang; Zhe-feng Pan; Jing Liu; Yue-yi Han; Yong Ding; Peng Song
2012-01-01
Density functional theory and time-dependent density-functional theory have been used to investigate the photophysical properties and relaxation dynamics of dimethylaminobenzophenone (DMABP) and its hydrogen-bonded DMABP-MeOH dimer.It is found that,in nonpolar aprotic solvent,the transitions from S0 to S1 and S2 states of DMABP have both n→π* and π→π* characters,with the locally excited feature mainly located on the C=O group and the partial CT one characterized by electron transfer mainly from the dimethylaminophenyl group to the C=O group.But when the intermolecular hydrogen bond C=O…H-O is formed,the highly polar intramolecular charge transfer character switches over to the first excited state of DMABP-MeOH dimer and the energy difference between the two lowlying electronically excited states increases.To gain insight into the relaxation dynamics of DMABP and DMABP-MeOH dimer in the excited state,the potential energy curves for conformational relaxation are calculated.The formation of twisted intramolecular charge transfer state via diffusive twisting motion of the dimethylamino/dimethylaminophenyl groups is found to be the major relaxation process.In addition,the decay of the S1 state of DMABP-MeOH dimer to the ground state,through nonradiative intermolecular hydrogen bond stretching vibrations,is facilitated by the formation of the hydrogen bond between DMABP and alcohols.
Gebremariam, B.; Bogner, S. K.; Duguet, T.
2010-01-01
The density matrix expansion (DME) of Negele and Vautherin is a convenient tool to map finite-range physics associated with vacuum two- and three-nucleon interactions into the form of a Skyme-like energy density functional (EDF) with density-dependent couplings. In this work, we apply the improved formulation of the DME proposed recently in arXiv:0910.4979 by Gebremariam {\\it et al.} to the non-local Fock energy obtained from chiral effective field theory (EFT) two-nucleon (NN) interactions a...
Goiffon, Vincent; Virmontois, Cédric; Magnan, Pierre; Girard, Sylvain; Paillet, Philippe
2010-01-01
The origin of total ionizing dose induced dark current in CMOS image sensors is investigated by comparing dark current measurements to interface state density and trapped charge density measurements. Two types of photodiode and several thick-oxide-FETs were manufactured using a 0,18 um CMOS image sensor process and exposed to 10 keV X-ray from 3 krad to 1 Mrad. It is shown that the radiation induced trapped charge extends the space charge region at the oxide interface, leading to an enhanceme...
Hammer, Maria S; Rauh, Daniel; Deibel, Carsten; Dyakonov, Vladimir
2008-01-01
Charge transport properties of thin films of sol--gel processed undoped and Al-doped zinc oxide nanoparticles with variable doping level between 0.8 at% and 10 at% were investigated. The X-ray diffraction studies revealed a decrease of the average crystallite sizes in highly doped samples. We provide estimates of the conductivity and the resulting charge carrier densities with respect to the doping level. The increase of charge carrier density due to extrinsic doping were compared to the accu...
Tsuchiizu, Masahisa; Yamakawa, Youichi; Kontani, Hiroshi
2016-04-01
The discovery of the charge-density-wave formation in the high-Tc cuprate superconductors has activated intensive theoretical studies for the pseudogap states. However, the microscopic origin of the charge-density-wave state has been unknown so far since the many-body effects beyond the mean-field-level approximations, called the vertex corrections, are essential. Toward solving this problem, we employ the recently developed functional renormalization group method, by which we can calculate the higher-order vertex corrections in a systematic and unbiased way with high numerical accuracy. We discover the critical development of the p -orbital-density-wave (p -ODW) instability in the strong-spin-fluctuation region. The obtained p -ODW state possesses the key characteristics of the charge-ordering pattern in Bi- and Y-based superconductors, such as the wave vector parallel to the nearest Cu-Cu direction, and the d -symmetry form factor with the antiphase correlation between px and py orbitals in the same unit cell. In addition, from the observation of the beautiful scaling relation between the spin susceptibility and the p -ODW susceptibility, we conclude that the main driving force of the density wave is the Aslamazov-Larkin vertex correction that becomes very singular near the magnetic quantum-critical point.
Interplay of charge density wave and multiband superconductivity in 2H-PdxTaSe2.
Bhoi, D; Khim, S; Nam, W; Lee, B S; Kim, Chanhee; Jeon, B-G; Min, B H; Park, S; Kim, Kee Hoon
2016-01-01
2H-TaSe2 has been one of unique transition metal dichalcogenides exhibiting several phase transitions due to a delicate balance among competing electronic ground states. An unusual metallic state at high-T is sequentially followed by an incommensurate charge density wave (ICDW) state at ≈122 K and a commensurate charge density wave (CCDW) state at ≈90 K, and superconductivity at TC ~ 0.14 K. Upon systematic intercalation of Pd ions into TaSe2, we find that CCDW order is destabilized more rapidly than ICDW to indicate a hidden quantum phase transition point at x ~ 0.09-0.10. Moreover, TC shows a dramatic enhancement up to 3.3 K at x = 0.08, ~24 times of TC in 2H-TaSe2, in proportional to the density of states N(EF). Investigations of upper critical fields Hc2 in single crystals reveal evidences of multiband superconductivity as temperature-dependent anisotropy factor γH = , quasi-linear increase of , and an upward, positive-curvature in near TC. Furthermore, analysis of temperature-dependent electronic specific heat corroborates the presence of multiple superconducting gaps. Based on above findings and electronic phase diagram vs x, we propose that the increase of N(EF) and effective electron-phonon coupling in the vicinity of CDW quantum phase transition should be a key to the large enhancement of TC in PdxTaSe2. PMID:27045426
Sun, Guangyu; Kurti, Jeno; Kertesz, Miklos; Baughman, Ray H.
2002-10-01
Charge-induced dimensional changes allow conducting polymers and single walled carbon nanotubes to function as electromechanical actuators. The unit cell of the prototypical conducting polymer, trans-polyacetylene, was calculated as a function of charge injection using density functional theory in combination with ultrasoft pseudopotentials using the solid-state Vienna ab initio simulation package. Test calculations on the charged pyridinium molecular ion give results in good agreement with the experimental geometry. Strain versus charge relationships are predicted from dimensional changes calculated using a uniform background charge ("jellium") for representing the counterions, which we show provides results consistent with experiment for doped polyacetylenes. These jellium calculations are consistent with further presented calculations that include specific counterions, showing that hybridization between the guest dopant ions and the host polyacetylene chains is unimportant. The lack of guest-host orbital hybridization allows a qualitative rigid band interpretation of the amount of charge transfer for both acceptor and donor doping. For polyacetylene, asymmetry of strain along the chain with respect to the sign of the charge is predicted: negative charge elongates and positive charge shortens the polymer. For charge less than 0.05e per carbon, an approximately linear dependence is obtained for the dependence of chain-direction strain on the amount of injected charge.
Kaihan Fakhar
Full Text Available OBJECTIVE: We aimed in this investigation to study deep brain stimulation (DBS battery drain with special attention directed toward patient symptoms prior to and following battery replacement. BACKGROUND: Previously our group developed web-based calculators and smart phone applications to estimate DBS battery life (http://mdc.mbi.ufl.edu/surgery/dbs-battery-estimator. METHODS: A cohort of 320 patients undergoing DBS battery replacement from 2002-2012 were included in an IRB approved study. Statistical analysis was performed using SPSS 20.0 (IBM, Armonk, NY. RESULTS: The mean charge density for treatment of Parkinson's disease was 7.2 µC/cm(2/phase (SD = 3.82, for dystonia was 17.5 µC/cm(2/phase (SD = 8.53, for essential tremor was 8.3 µC/cm(2/phase (SD = 4.85, and for OCD was 18.0 µC/cm(2/phase (SD = 4.35. There was a significant relationship between charge density and battery life (r = -.59, p<.001, as well as total power and battery life (r = -.64, p<.001. The UF estimator (r = .67, p<.001 and the Medtronic helpline (r = .74, p<.001 predictions of battery life were significantly positively associated with actual battery life. Battery status indicators on Soletra and Kinetra were poor predictors of battery life. In 38 cases, the symptoms improved following a battery change, suggesting that the neurostimulator was likely responsible for symptom worsening. For these cases, both the UF estimator and the Medtronic helpline were significantly correlated with battery life (r = .65 and r = .70, respectively, both p<.001. CONCLUSIONS: Battery estimations, charge density, total power and clinical symptoms were important factors. The observation of clinical worsening that was rescued following neurostimulator replacement reinforces the notion that changes in clinical symptoms can be associated with battery drain.
On the Control of the Fixed Charge Densities in Al2O3-Based Silicon Surface Passivation Schemes.
Simon, Daniel K; Jordan, Paul M; Mikolajick, Thomas; Dirnstorfer, Ingo
2015-12-30
A controlled field-effect passivation by a well-defined density of fixed charges is crucial for modern solar cell surface passivation schemes. Al2O3 nanolayers grown by atomic layer deposition contain negative fixed charges. Electrical measurements on slant-etched layers reveal that these charges are located within a 1 nm distance to the interface with the Si substrate. When inserting additional interface layers, the fixed charge density can be continuously adjusted from 3.5 × 10(12) cm(-2) (negative polarity) to 0.0 and up to 4.0 × 10(12) cm(-2) (positive polarity). A HfO2 interface layer of one or more monolayers reduces the negative fixed charges in Al2O3 to zero. The role of HfO2 is described as an inert spacer controlling the distance between Al2O3 and the Si substrate. It is suggested that this spacer alters the nonstoichiometric initial Al2O3 growth regime, which is responsible for the charge formation. On the basis of this charge-free HfO2/Al2O3 stack, negative or positive fixed charges can be formed by introducing additional thin Al2O3 or SiO2 layers between the Si substrate and this HfO2/Al2O3 capping layer. All stacks provide very good passivation of the silicon surface. The measured effective carrier lifetimes are between 1 and 30 ms. This charge control in Al2O3 nanolayers allows the construction of zero-fixed-charge passivation layers as well as layers with tailored fixed charge densities for future solar cell concepts and other field-effect based devices. PMID:26618751
Ayuel, K.; de Châtel, P. F.; Amani, Salah
2002-04-01
Charge, current and spin densities are calculated for a two-electron system, maintaining the explicit form of the wave functions, in terms of Slater determinants. The two-electron Russell-Saunders spin-orbit coupled eigenstates | L, S, J, MJ> are expressed as four-component spinors, and the operators of the above densities as 4×4 matrices. The contributions of various one-electron states to these densities are identified.
Impurity-Mediated Early Condensation of a Charge Density Wave in an Atomic Wire Array.
Yeom, Han Woong; Oh, Deok Mahn; Wippermann, Stefan; Schmidt, Wolf Gero
2016-01-26
We directly show how impurity atoms induce the condensation of a representative electronic phase, the charge density wave (CDW) phase, in atomic scale with scanning tunneling microscopy. Oxygen impurity atoms on the self-assembled metallic atomic wire array on a silicon crystal condense the CDW locally above the pristine transition temperature. More interestingly, the CDW along the wires is induced not by a single atomic impurity but by the cooperation of multiple impurities. First-principles calculations disclose the mechanism of the cooperation as the coherent superposition of the local lattice strain induced by impurities, stressing the coupled electronic and lattice degrees of freedom for the CDW. This opens the possibility of the strain engineering over electronic phases of atomic-scale systems. PMID:26634634
After having recalled that elastic electron scattering allows the determination of nucleus charge density with a high precision, and that a sufficiently high momentum transfer is required for the precision of analysis methods, this research thesis presents the results obtained by an experiment performed on 208Pb with a high momentum transfer. This nucleus meets at best the approximations required by theoretical calculations. In a first part, the author discusses the use of this nucleus, discusses the available data and outlines the lacking ones. He presents the experimental installation and aspects: the linear accelerator, the scattering angle, the solid angle, the number of incident neutrons, the target thermal toughness, and the number of elastically scattered neutrons. He reports the reduction of data: experiment-based corrections, radiative corrections, spectrum deconvolution methods, data normalisation, diaphragm aperture corrections and multiple scattering corrections. The next part proposes an analysis of data, and the last one compares the obtained results with theoretical ones
Subgap Collective Tunneling and Its Staircase Structure in Charge Density Waves
Tunneling spectra of chain materials NbSe3 and TaS3 were studied in nanoscale mesa devices. Current-voltage I-V characteristics related to all charge density waves (CDWs) reveal universal spectra within the normally forbidden region of low V, below the electronic CDW gap 2Δ. The tunneling always demonstrates a threshold Vt≅0.2Δ, followed, for both CDWs in NbSe3, by a staircase fine structure. T dependencies of Vt(T) and Δ(T) scale together for each CDW, while the low T values Vt(0) correlate with the CDWs' transition temperatures Tp. Fine structures of CDWs perfectly coincide when scaled along V/Δ. The results evidence the sequential entering of CDW vortices (dislocations) in the junction area with the tunneling current concentrated in their cores. The subgap tunneling proceeds via the phase channel: coherent phase slips at neighboring chains