Extraction of effective ion pair interactions in warm dense beryllium and helium plasmas within integral equation theory

Ye, Jingxin; Zhao, Bin; Zheng, Jian

doi:10.1063/1.3559489

Cited by 13 publications

(6 citation statements)

References 25 publications

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“…At temperatures below 4 eV, the PCF computed with the SC-MD method are dramatically different from those computed with DFT-MD or EFF-MD. In particular, the short-range behavior of the PCF from our SC-MD simulations is indicative of a potential that is too soft at small r. This is consistent with previous studies where a short-range repulsive modification to an LSC potential was shown to improve agreement with DFT-MD [36,37]. This approach is based on finding a potential that gives a solution to the Ornstein-Zernicke integral equations www.cpp-journal.org that is consistent with data from DFT-MD.…”

Section: Pair Correlation Functionssupporting

confidence: 91%

“…For all temperatures where we have reported the ionic specific heat, we set Z = 3.2e and κ = 2.6Å −1 . The shape of the LSC potential at short range is not consistent with the DFT-MD force-matched potentials, so we expect that it will not provide a good description of carbon at the conditions studied here, in agreement with what has been observed in previous studies of other elements where a correction to the LSC has been applied at short range [36,37,40].…”

Section: Specific Heatsupporting

confidence: 68%

“…We note that, while the approach of Refs. [36,37] may provide an adequate description of the ionic correlations at higher temperatures, it does not address why an apparent "attraction" occurs. We do not observe any attractive (defined by negative interaction potential) regions in our force matched potentials.…”

Section: Pair Correlation Functionsmentioning

confidence: 99%

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Molecular Dynamics Simulations of Warm Dense Carbon

Whitley

Sanchez

Hamel

et al. 2015

Contrib. Plasma Phys.

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We present classical and DFT-based molecular dynamics (MD) simulations of carbon in the warm dense matter regime (ρ= 3.7 g/cc, 0.86 eV < T < 8.62 eV [T < 100 eV for classical MD]). Two different classical interatomic potentials are used: 1. LCBOP, designed to simulate condensed (e.g. solid) phases of C, and 2. linearly screened Coulomb (Yukawa) potentials. It is shown that LCBOP over-predicts minima and maxima in the pair correlation functions of liquid-C in this regime when compared to the DFT-MD results. The screened Coulomb model, while under-correlating at low-T , seems to produce the correct qualitative features in the static ionic pair distributions at the highest-T . However, both approaches predict the decay in the ionic contribution of the specific heat as T −→ ∞ to be much slower than that predicted by a model based on DFT-MD. These differences in the MD-derived equations of state in warm dense regimes could have important consequences when using classical inter-ionic forces such as these in large-scale MD simulations aimed at studying, for instance, processes of relevance to inertial confinement fusion when C is used as an ablator material.

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Section: Pair Correlation Functionssupporting

confidence: 91%

Section: Specific Heatsupporting

confidence: 68%

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Molecular Dynamics Simulations of Warm Dense Carbon

Whitley

Sanchez

Hamel

et al. 2015

Contrib. Plasma Phys.

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“…For a few years, the behavior of warm dense beryllium has been an issue of interest from both a theoretical and experimental point of view [15,16,17,18,19,20,13]. The recent possibility to carry out comparisons with different approaches motivates our interest to develop a pure classical investigation based on classical MD.…”

Section: Application To Berylliummentioning

confidence: 99%

Warm dense matter through classical molecular dynamics

Calisti

Ferri

Marciante

et al. 2014

High Energy Density Physics

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A classical Molecular Dynamics code has been developed to simulate dense plasmas i.e. neutral systems of interacting ions and electrons. Our goal is to design a tool that relies on a reduced set of microscopic mechanisms in order to obtain solutions of complex time dependent n-body problems and to allow an efficient description of the plasma states between classical high temperature systems to strongly coupled plasmas. Our present objective is an attempt to explore the behavior of such a classical approach for typical conditions of warm dense matter. We calculate the dynamic structure factor in warm dense beryllium by means of our molecular dynamics simulations. The results are then compared with those obtained within the framework of the random phase approximation (RPA).

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“…The complexity of WDM, compressions and temperatures involved call for simplifications without sacrificing accuracy. Thus molecular dynamics (MD), i.e., classical simulations, using various effective potentials have been a focus of some recent studies [8,9]. Such methods were used in earlier work [10], often with phenomenological or 'chemical' models for pairinteractions, and in recent studies as well [12].…”

Section: Introductionmentioning

confidence: 99%

Electron-ion and ion-ion potentials for modeling warm dense matter: Applications to laser-heated or shock-compressed Al and Si

Dharma‐wardana

2012

Phys. Rev. E

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The pair-interactions Uij (r) determine the thermodynamics and linear transport properties of matter via the pair-distribution functions (PDFs), i.e., gij(r). Great simplicity is achieved if Uij (r) could be directly used to predict material properties via classical simulations, avoiding many-body wavefunctions. Warm dense matter (WDM) is encountered in quasi-equilibria where the electron temperature Te differs from the ion temperature Ti, as in laser-heated or in shock-compressed matter. The electron PDFs gee(r) as perturbed by the ions are used to evaluate fully non-local exchangecorrelation corrections to the free energy, using Hydrogen as an example. Electron-ion potentials for ions with a bound core are discussed with Al and Si as examples, for WDM with Te = Ti, and valid for times shorter than the electron-ion relaxation time. In some cases the potentials develop attractive regions, and then become repulsive and 'Yukawa-like' for higher Te. These results clarify the origin of initial phonon-hardening and rapid release. Pair-potentials for shock-heated WDM show that phonon hardening would not occur in most such systems. Defining meaningful quasi-equilibrium static transport coefficients consistent with the dynamic values is addressed. There seems to be no meaningful 'static conductivity' obtainable by extrapolating experimental or theoretical σ(ω, Ti, Te) to ω → 0, unless Ti → Te as well. Illustrative calculations of quasi-static resistivities R(Ti, Te) of laser-heated as well as shock-heated Aluminum and Silicon are presented using our pseudopotentials, pair-potentials and classical integral equations. The quasi-static resistivities display clear differences in their temperature evolutions, but are not the strict ω → 0 limits of the dynamic values.

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Extraction of effective ion pair interactions in warm dense beryllium and helium plasmas within integral equation theory

Cited by 13 publications

References 25 publications

Molecular Dynamics Simulations of Warm Dense Carbon

Molecular Dynamics Simulations of Warm Dense Carbon

Warm dense matter through classical molecular dynamics

Electron-ion and ion-ion potentials for modeling warm dense matter: Applications to laser-heated or shock-compressed Al and Si

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