Thermophysical properties of hydrogen-helium mixtures: Re-examination of the mixing rules via quantum molecular dynamics simulations

TL;DR

This study uses quantum molecular dynamics to evaluate the thermophysical properties of hydrogen-helium mixtures, validating mixing rules and providing insights into their accuracy in warm dense matter conditions.

Contribution

It re-examines the validity of common mixing rules for hydrogen-helium mixtures using detailed QMD simulations in the warm dense matter regime.

Findings

Mixing rules reproduce pressure within 10% accuracy.

Diffusion and viscosity predictions are less accurate, with 75% and 50% agreement.

Binary ionic mixing rule improves the agreement for composite properties.

Abstract

Thermophysical properties of hydrogen, helium, and hydrogen-helium mixtures have been investigated in the warm dense matter regime at electron number densities ranging from $6.02\times10^{29}\sim2.41\times10^{30}$/m$^{3}$ and temperatures from 4000 to 20000 K via quantum molecular dynamics simulations. We focus on the dynamical properties such as the equation of states, diffusion coefficients, and viscosity. Mixing rules (density matching, pressure matching, and binary ionic mixing rules) have been validated by checking composite properties of pure species against that of the fully interacting mixture derived from QMD simulations. These mixing rules reproduce pressures within 10% accuracy, while it is 75% and 50% for the diffusion and viscosity, respectively. Binary ionic mixing rule moves the results into better agreement. Predictions from one component plasma model are also provided and discussed.