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Molecular dynamics studies of electron-ion temperature equilibration in hydrogen plasmas within the coupled-mode regime

Lorin X. Benedict, Michael P. Surh, Liam G. Stanton, Christian R. Scullard, Alfredo A. Correa, John I. Castor, and Frank R. Graziani

Lee A. Collins, Ondřej Čertík, and Joel D. Kress

Michael S. Murillo

Lawrence Livermore National Laboratory, Livermore, California 94550, USA

Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

Department of Computational Mathematics, Science and Engineering, Michigan State University, East Lansing, Michigan 48824, USA

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Phys. Rev. E 95, 043202 – Published 10 April, 2017

DOI: https://doi.org/10.1103/PhysRevE.95.043202

Abstract

We use classical molecular dynamics (MD) to study electron-ion temperature equilibration in two-component plasmas in regimes for which the presence of coupled collective modes has been predicted to substantively reduce the equilibration rate. Guided by previous kinetic theory work, we examine hydrogen plasmas at a density of $n = 10^{26} {cm}^{- 3}, T_{i} = 10^{5} K$ , and $10^{7} K < T_{e} < 10^{9} K$ . The nonequilibrium classical MD simulations are performed with interparticle interactions modeled by quantum statistical potentials (QSPs). Our MD results indicate (i) a large effect from time-varying potential energy, which we quantify by appealing to an adiabatic two-temperature equation of state, and (ii) a notable deviation in the energy equilibration rate when compared to calculations from classical Lenard-Balescu theory including the QSPs. In particular, it is shown that the energy equilibration rates from MD are more similar to those of the theory when coupled modes are neglected. We suggest possible reasons for this surprising result and propose directions of further research along these lines.

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References (74)

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Molecular dynamics studies of electron-ion temperature equilibration in hydrogen plasmas within the coupled-mode regime

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