Precise Diffusion Coefficients for White Dwarf Astrophysics

TL;DR

This paper provides high-precision diffusion coefficients for white dwarf modeling using molecular dynamics simulations, significantly improving the accuracy of stellar evolution predictions.

Contribution

It introduces a new physically motivated diffusion law with a semi-empirical correction, validated at the percent level, for use in white dwarf simulations.

Findings

Diffusion coefficients calculated with high resolution for relevant regimes.

A new diffusion law with semi-empirical correction improves accuracy.

Implementation reduces diffusion-related errors by an order of magnitude.

Abstract

Observations of galactic white dwarfs with Gaia have allowed for unprecedented modeling of white dwarf cooling, resolving core crystallization and sedimentary heating from neutron rich nuclei. These cooling sequences are sensitive to the diffusion coefficients of nuclei in Coulomb plasmas which have order 10\% uncertainty and are often not valid across coupling regimes. Using large scale molecular dynamics simulations we calculate diffusion coefficients at high resolution in the regime relevant for white dwarf modeling. We present a physically motivated law for diffusion with a semi-empirical correction which is accurate at the percent level. Implemented along with linear mixing in stellar evolution codes, this law should reduce the error from diffusion coefficients by an order of magnitude.