Quantum molecular dynamics simulations of warm dense lithium hydride: Examination of mixing rules

Abstract

We have performed a systematic study of lithium hydride (LiH) in a density range from half to twice solid for temperatures from $0.5\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}3.0\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ using quantum molecular dynamics (QMD) methods and have tested density and pressure mixing rules for obtaining equations of state and optical properties such as frequency-dependent absorption coefficients and Rosseland mean opacities. The QMD simulations for the full LiH fluid served as a benchmark against which to assess the rules. In general, the mixing rule based on the pressure matching produces superior equations of state and mean opacities for the mixture except at the very lowest temperatures and densities. However, the frequency-dependent absorption coefficients displayed considerable differences in some frequency ranges except at the highest temperatures and densities.