Yukawa Friedel-Tail pair potentials for warm dense matter applications

TL;DR

This paper introduces a simple Yukawa Friedel-Tail (YFT) pair potential model that accurately fits and extrapolates NPA and DFT-MD potentials for warm dense matter, enabling efficient large-scale multi-species plasma simulations.

Contribution

The paper develops a physically motivated analytic YFT pair potential model that simplifies and accelerates the generation of EOS and transport data for warm dense matter.

Findings

YFT model accurately fits NPA and DFT-MD pair potentials.

YFT provides reliable extrapolations for various particle separations.

Model applicable to multi-species warm dense matter simulations.

Abstract

Accurate equations of state (EOS) and plasma transport properties are essential for numerical simulations of warm dense matter encountered in many high-energy-density situations. Molecular dynamics (MD) is a simulation method that generates EOS and transport data using an externally provided potential to dynamically evolve the particles without further reference to the electrons. To minimize computational cost, pair potentials needed in MD may be obtained from the neutral-pseudoatom (NPA) approach, a form of single-ion density functional theory (DFT), where many-ion effects are included via ion-ion correlation functionals. Standard $N$-ion DFT-MD provides pair potentials via the force matching technique but at much greater computational cost. Here we propose a simple analytic model for pair potentials with physically meaningful parameters based on a Yukawa form with a thermally damped Friedel tail (YFT) applicable to systems containing free electrons. The YFT model accurately fits NPA pair potentials or the non-parametric force-matched potentials from $N$-ion DFT-MD, showing excellent agreement for a wide range of conditions. The YFT form provides accurate extrapolations of the NPA or force-matched potentials for small and large particle separations within a physical model. Our method can be adopted to treat plasma mixtures, allowing for large-scale simulations of multi-species warm dense matter.