Modified Enskog Kinetic Theory for Strongly Coupled Plasmas

TL;DR

This paper extends the Enskog kinetic theory to strongly coupled plasmas by incorporating short-range correlations and an exclusion radius, improving predictions of transport coefficients like diffusion and viscosity.

Contribution

It introduces a novel adaptation of Enskog theory for plasmas, including an exclusion radius to account for Coulomb repulsion, and tests its accuracy against molecular dynamics simulations.

Findings

Accurately predicts self-diffusion coefficients for plasmas.

Effectively captures shear viscosity at moderate coupling.

Less accurate for potential contributions at very strong coupling.

Abstract

Concepts underlying the Enskog kinetic theory of hard-spheres are applied to include short-range correlation effects in a model for transport coefficients of strongly coupled plasmas. The approach is based on an extension of the effective potential transport theory [S.~D.~Baalrud and J.~Daligault, Phys.~Rev.~Lett.~{\bf 110}, 235001 (2013)] to include an exclusion radius surrounding individual charged particles that is associated with Coulomb repulsion. This is obtained by analogy with the finite size of hard spheres in Enskog's theory. Predictions for the self-diffusion and shear viscosity coefficients of the one-component plasma are tested against molecular dynamics simulations. The theory is found to accurately capture the kinetic contributions to the transport coefficients, but not the potential contributions that arise at very strong coupling ($\Gamma \gtrsim 30$). Considerations related to a first-principles generalization of Enskog's kinetic equation to continuous potentials are also discussed.