The structure of warm dense matter modeled with an average atom model with ion-ion correlations

TL;DR

This paper introduces a computationally efficient average atom model for warm dense matter that incorporates ion-ion correlations via fluid theory, validated against ab initio simulations, and useful for property calculations.

Contribution

It develops a new intermediate model combining average atom and fluid correlation theories, expanding the realism of warm dense matter simulations with manageable computational cost.

Findings

Model accurately reproduces ion pair distribution functions.

Simpler theories are recovered in limiting cases.

Validated against ab initio simulation data.

Abstract

We present a new model of warm dense matter that represents an intermediate approach between the relative simplicity of ''one-ion'' average atom models and the more realistic but computationally expensive ab initio simulation methods. Physical realism is achieved primarily by including the correlations in the plasma that surrounds a central ion. The plasma is described with the Ornstein-Zernike integral equations theory of fluids, which is coupled to an average atom model for the central ion. In this contribution we emphasize the key elements and approximations and how they relate to and expand upon a typical average atom model. Besides being relatively inexpensive computationally, this approach offers several advantages over ab initio simulations but also has a number of limitations. The model is validated by comparisons with numerical solutions for the pair distribution function of the ions from ab initio simulations for several elements and a wide range of plasma conditions. Simulations results are reproduced remarkably well and simpler limiting theories are recovered as well. This model has many potential applications to calculation of the properties of warm dense matter such as the equation of state and conductivities for a wide range of temperatures and densities.