Effective Potential and Interdiffusion in Binary Ionic Mixtures

TL;DR

This paper develops a method to accurately calculate interdiffusion coefficients in binary ionic mixtures across weak to strong Coulomb coupling regimes, applicable to astrophysical plasma environments.

Contribution

It introduces an effective potential approach extending Chapman-Enskog theory to strongly coupled plasmas, providing practical formulas for diverse astrophysical conditions.

Findings

Computed binary diffusion coefficients for various ionic mixtures.

Provided fitting formulas for diffusion coefficients over wide plasma parameters.

Validated the method for applications in stellar and compact object modeling.

Abstract

We calculate interdiffusion coefficients in a two-component, weakly or strongly coupled ion plasma (gas or liquid, composed of two ion species immersed into a neutralizing electron background). We use an effective potential method proposed recently by Baalrud and Daligaut [PRL, 110, 235001, (2013)]. It allows us to extend the standard Chapman-Enskog procedure of calculating the interdiffusion coefficients to the case of strong Coulomb coupling. We compute binary diffusion coefficients for several ionic mixtures and fit them by convenient expressions in terms of the generalized Coulomb logarithm. These fits cover a wide range of plasma parameters spanning from weak to strong Coulomb couplings. They can be used to simulate diffusion of ions in ordinary stars as well as in white dwarfs and neutron stars.