Pseudopotential and full-electron DFT calculations of thermodynamic properties of electrons in metals and semiempirical equations of state

Levashov, P. R.; Sin'ko, G. V.; Smirnov, N. A.; Minakov, D. V.; Shemyakin, O P; Khishchenko, K. V.

doi:10.1088/0953-8984/22/50/505501

Cited by 42 publications

(21 citation statements)

References 27 publications

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“…Satisfaction of some computational threshold for the smallest non-negligible occupation number requires an increasingly large set of those virtuals to be considered with increasing T. Concurrently there is [36] found that for ambient density Al, the PAW pressure deviated from the all-electron value at about T = 5-6 eV. This is less than 10% of the magnitude of the LSDA 2p atomic KS eigenvalue (about 70 eV).…”

Section: Finite Temperatures a Pseudopotentials And Level Populamentioning

confidence: 99%

“…That threshold is directly related to basis set size or, equivalently, the plane-wave cutoff. We know of only one study of any of these questions [36]. In it, all-electron calculations with the full-potential linearized muffin-tin orbital methodology were used to benchmark projector augmented wave (PAW) calculations with a plane wave basis.…”

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confidence: 99%

“…Additionally, Ref. 36 used the free-electron expression for the non-interacting electronic entropy, rather than the proper explicit dependence on occupation numbers f i :…”

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confidence: 99%

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Comparison of density functional approximations and the finite-temperature Hartree-Fock approximation in warm dense lithium

2012

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We compare the behavior of the finite-temperature Hartree-Fock model with that of thermal density functional theory using both ground-state and temperature-dependent approximate exchange functionals. The test system is bcc Li in the temperature-density regime of warm dense matter (WDM). In this exchange-only case, there are significant qualitative differences in results from the three approaches. Those differences may be important for Born-Oppenheimer molecular dynamics studies of WDM with ground-state approximate density functionals and thermal occupancies. Such calculations require reliable regularized potentials over a demanding range of temperatures and densities. By comparison of pseudopotential and all-electron results at T = 0 K for small Li clusters of local bcc symmetry and bond-lengths equivalent to high density bulk Li, we determine the density ranges for which standard projector augmented wave (PAW) and norm-conserving pseudopotentials are reliable. Then we construct and use all-electron PAW data sets with a small cutoff radius which are valid for lithium densities up to at least 80 g/cm 3 .

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Section: Finite Temperatures a Pseudopotentials And Level Populamentioning

confidence: 99%

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Comparison of density functional approximations and the finite-temperature Hartree-Fock approximation in warm dense lithium

2012

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“…Shell effects in condensed matter caused by both pressure and temperature were investigated by DFT [31]. In this case the thermal excitation of inner electrons takes place which causes oscillations of some thermodynamic functions.…”

Section: Resultsmentioning

confidence: 99%

“…At T > 0 the quantum molecular dynamics (QMD) method allows us to simulate a cubic supercell with up to 1000 ions; in the Born-Oppenheimer approximation quantum electrons are treated by DFT while the movement of classical ions obeys Newton's second law. As some electrons in a pseudopotential DFT approach are included into an invariable core this method is restricted both on temperature and density because of the excitation of core electrons [31]. Also in QMD additional error may appear when some particles move very close to each other at high enough temperatures [32].…”

Section: Methods Of Calculationmentioning

confidence: 99%

Influence of shell effects on thermodynamic properties of matter at high pressures

Levashov

Minakov

2018

J. Phys.: Conf. Ser.

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Abstract. We analyze the influence of shell effects on thermodynamic properties of matter at high pressures. Spherically symmetric average atom models show significant contribution of electronic transitions to cold pressure which is not confirmed by more accurate density functional theory models. In particular, the s-d transition in aluminum and potassium does not reveal itself on the shock Hugoniots. Oscillations on shock Hugoniots at very high pressures predicted earlier by many authors should be confirmed by precise first-principle calculations. IntroductionThermodynamic properties of matter at high pressure are of importance in many problems of high energy density physics, in particular, in astrophysics [1], in wide-range equations of state [2,3], in the problems of interaction of intense energy fluxes with matter [4-6], in perspective power generation facilities [7] and in some others. The finite-temperature Thomas-Fermi (TF) model [8] based upon semiclassical approximation is widely used to describe thermodynamic properties of matter, but there are many phenomena beyond this approach. In particular, shell effects reflect non-regularities of physical parameters because of the discrete energy spectrum. For example, in low-density plasma step-wise dependencies of thermodynamic functions on isochors or isobars are quite typical [9]. The other well-known effect is connected with the non-regular behavior of density of elements vs. atomic mass [10,11]. To describe shell effects one should take into account discrete energy levels. Analytically shell corrections to the TF model have been studied in [12,13] using the Poisson formula in the transition from summation to integration (see also the review [14]). Average atom models [15][16][17][18][19] are based on a radial solution of the single-particle Schrödinger (Dirac) equation so that the discrete spectrum and shell effects are taken into account implicitly. During the last 30 years it became possible to obtain approximate three-dimensional (3D) solutions of a quantum many-particle problem using density functional theory (DFT) [20,21]. In this case one gets a 3D band structure of a system of particles that provides for the appearance of shell effects through non-regularities of the electronic density and some thermodynamic functions. There were several attempts to register shell effects at high pressures and temperatures experimentally [22][23][24] using underground nuclear explosions. It is claimed [24] that the influence of the discrete energy spectrum is

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Electron‐Ion Relaxation, Phase Transitions, and Surface Nano‐Structuring Produced by Ultrashort Laser Pulses in Metals

Inogamov

Zhakhovsky

Petrov

et al. 2013

Contrib. Plasma Phys.

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Fundamental physical phenomena in metals irradiated by ultrashort laser pulses with absorbed fluences higher than few tens of mJ/cm2 are investigated. For those fluences, laser‐produced electron distribution function relaxes to equilibrium Fermi distribution with electron temperature Te within a short time of 10‐100 fs. Because the electron subsystem has Te highly exceeding much the ion subsystem temperature Ti the well‐known twotemperature hydrodynamic model (2T‐HD) is used to evaluate heat propagation associated with hot conductive electron diffusion and electron‐ion energy exchange. The model coefficients of electron heat conductivity κ (ϱ, Te, Ti) and electron‐ion coupling parameter α (ϱ, Te) together with 2T equation of state E (ϱ, Te, Ti) and P (ϱ, Te, Ti) are calculated. Modeling with 2T‐HD code shows transition of electron heat wave from supersonic to subsonic regime of prop‐agation. At the moment of transition the heat wave emits a compression wave moving into the bulk of met al. Nonlinear evolution of the compression wave after its separation from the subsonic heat wave till spallation of rear‐side layer of a film is traced in both 2T‐HD modeling and molecular dynamics (MD) simulation. For fluences above some threshold the nucleation of voids in frontal surface layer is initiated by strong tensile wave following the compression wave. If the absorbed fluence is ∼30 % above the ablation threshold than void nucleation develops quickly to heavily foam the molten met al. Long‐term evolution of the metal foam including foam breaking and freezing is simulated. It is shown that surface nano‐structures observed in experiments are produced by very fast cooling of surface molten layer followed by recrystallization of supercooled liquid in disintegrating foam having complex geometry. Characteristic lengths of such surface nanostructures, including frozen pikes and bubbles, are of the order of thickness of molten layer formed right after laser irradiation. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Pseudopotential and full-electron DFT calculations of thermodynamic properties of electrons in metals and semiempirical equations of state

Cited by 42 publications

References 27 publications

Comparison of density functional approximations and the finite-temperature Hartree-Fock approximation in warm dense lithium

Comparison of density functional approximations and the finite-temperature Hartree-Fock approximation in warm dense lithium

Influence of shell effects on thermodynamic properties of matter at high pressures

Electron‐Ion Relaxation, Phase Transitions, and Surface Nano‐Structuring Produced by Ultrashort Laser Pulses in Metals

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