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Yair Kurzweil

Publications and source records attributed to Yair Kurzweil.

8 recordsLinked to original sources
arXiv2018

The effect of ionic correlations on radiative properties in the solar interior and terrestrial experiments

Intending to solve the decade old problem of solar opacity, we report substantial photoabsorption uncertainty due to the effect of ion-ion correlations. By performing detailed opacity calculations of the solar mixture, we find that taking into account the ionic structure changes the Rosseland opacity near the convection zone by about 10%. We also report about 15% difference in the Rosseland opacity for iron, which was recently measured at the Sandia Z facility, where the temperature reached that prevailing in the convection zone boundary while the density is 2.5 times lower. Finally, we propose a method to measure opacities at solar temperatures and densities that were never reached in the past via laboratory radiation flow experiments, by using plastic foams doped with permilles of dominant photon absorbers in the Sun. The method is advantageous for an experimental study of solar opacities that may lead to a resolution of the solar problem.

astro-ph.SR↗
arXiv2008

Analysis of multi-configuration Kohn-Sham methods

We consider the extension of the standard single-determinant Kohn-Sham method to the case of a multiconfiguration trial wavefunction. By applying the rigorous Kohn-Sham method to this case, we construct the proper interacting and non-interacting energy functionals. Following the Hohenberg-Kohn theorem for both energy functionals, we derive the corre-sponding multiconfiguration Kohn-Sham equations. At the end of the analysis we show that, at the ground state, the multiconfiguration wavefunction must collapse into a single-determinant wavefunction, equal to the regular KS wavefunction. We also discuss the non-collapse of the wavefunction in other multiconfiguration density functional theory methods where the auxiliary system is partially interacting.

cond-mat.str-el↗
arXiv2007

Adapting approximate memory potentials for time-dependent density functional theory

Frequency dependent exchange correlation kernels for time-dependent density functional theory can be used to construct approximate exchange-correlation potentials. The resulting potentials are usually not translationally covariant nor do they obey the so-called zero-force condition. These two basic symme-try requirements are essential for using the potentials in actual applications (even within the linear re-sponse regime). We provide two pragmatic methods for imposing these conditions. As an example we take the Gross and Kohn (GK) frequency dependent XC functional (Phys. Rev.Lett. 55, 2850 (1985)), correct it, and numerically test it on a sodium metal cluster. Violation of the basic symme-tries causes instabilities or spurious low frequency modes.

cond-mat.str-el↗
arXiv2005

Quantum memory effects on the dynamics of electrons in gold clusters

Electron dynamics in metallic clusters are examined using a time-dependent density functional theory that in-cludes a "memory term", i.e. attempts to describe temporal non-local correlations. Using the Iwamoto, Gross and Kohn exchange-correlation (XC) kernel we construct a translationally invariant memory action from which an XC potential is derived that is translationally covariant and exerts zero net force on the electrons. An efficient and stable numerical method to solve the resulting Kohn-Sham equations is presented. Using this framework, we study memory effects on electron dynamics in spherical Jellium "gold clusters". We find memory significantly broadens the surface plasmon absorption line, yet considerably less than measured in real gold clusters, attributed to the inadequacy of the Jellium model. Two-dimensional pump-probe spectroscopy is used to study the temporal decay profile of the plasmon, finding a fast decay followed by slower tail. Finally, we examine memory effects on high harmonic generation, finding memory narrows emission lines.

cond-mat.str-el↗
arXiv2005

Quantum memory effects on the dynamics of electrons in small gold clusters

Electron dynamics in metallic clusters are examined using a time-dependent density functional theory that includes a 'memory term', i.e. attempts to describe temporal non-local correlations. Using the Iwamoto, Gross and Kohn exchange-correlation (XC) kernel we construct a translationally invariant memory action from which an XC potential is derived that is translationally covariant and exerts zero net force on the electrons. An efficient and stable numerical method to solve the resulting Kohn-Sham equations is presented. Using this framework, we study memory effects on electron dynamics in spherical Jellium 'gold clusters'. We find memory significantly broadens the surface plasmon absorption line, yet considerably less than measured in real gold clusters, attributed to the inadequacy of the Jellium model. Two-dimensional pump-probe spectroscopy is used to study the temporal decay profile of the plasmon, finding a fast decay followed by slower tail. Finally, we examine memory effects on high harmonic generation, finding memory narrows emission lines.

cond-mat.str-el↗
arXiv2005

Generic Galilean invariant exchange correlation functionals with quantum memory

Today, most application of time-dependent density functional theory (TDDFT) use adiabatic exchange-correlation (XC) potentials that do not take into account non-local temporal effects. Incorporating such "memory" terms into XC potentials is complicated by the constraint that the derived force and torque densities must integrate to zero at every instance. This requirement can be met by deriving the potentials from an XC action that is Galilean in-variant (GI). We develop a class of simple but flexible forms for an action that respect these constraints. The basic idea is to formulate the action in terms of the Eularian-Lagrangian transformation (ELT) metric tensor, which is itself GI. The general form of the XC potentials in this class is then derived and the linear response limit is derived as well.

cond-mat.str-el↗
arXiv2004

Galilean invariant exchange correlation functionals with quantum memory

Today, most application of time-dependent density functional theory (TDDFT) use adiabatic exchange-correlation (XC) potentials that do not take into account non-local temporal effects. Incorporating such "memory" terms into XC potentials is complicated by the constraint that the derived force and torque densities must integrate to zero at every instance. This requirement can be met by deriving the potentials from an XC action that is Galilean in-variant (GI). We develop a class of simple but flexible forms for an action that respect these constraints. The basic idea is to formulate the action in terms of the Eularian-Lagrangian transformation (ELT) metric tensor, which is itself GI. The general form of the XC potentials in this class is then derived and the linear response limit is derived as well.

cond-mat.str-el↗
arXiv2004

Time-dependent exchange-correlation current density functionals with memory

Most present applications of time-dependent density functional theory use adiabatic functionals, i.e. the effective potential at time t is determined solely by the density at the same time. This paper discusses a method that aims to go beyond this approximation, by incorporating "memory" effects: the potential will depend also on the history. We add to the adiabatic approximation an additional part that includes memory and yields a functional that is totally consis-tent with known dynamical properties of the homogeneous electron gas (in the linear response limit). In order to achieve this, we write down an action principle from which Kohn-Sham equations are derived for description of the time-dependent electron density and fluid velocity field. The action principle is built in such a way that it is Galilean invariant and yields causal equations.

cond-mat.str-el↗