Reconciling ionization energies and band gaps of warm dense matter derived with ab initio simulations and average atom models

TL;DR

This paper introduces AVION, a novel average atom model that accurately predicts electronic properties of warm dense matter, reconciling previous discrepancies with ab initio simulations by using innovative boundary conditions.

Contribution

The paper develops AVION, an advanced AA model with new boundary conditions that align its predictions with ab initio results for high-pressure materials.

Findings

AVION accurately predicts band structures of carbon and aluminum.

It resolves previous inconsistencies between AA models and ab initio simulations.

The model improves understanding of electronic properties in warm dense matter.

Abstract

Average atom (AA) models allow one to efficiently compute electronic and optical properties of materials over a wide range of conditions and are often employed to interpret experimental data. However, at high pressure, predictions from AA models have been shown to disagree with results from ab initio computer simulations. Here we reconcile these deviations by developing an innovative type of AA model, AVION, that computes the electronic eigenstates with novel boundary conditions within the ion sphere. Bound and free states are derived consistently. We drop the common AA image that the free-particle spectrum starts at the potential threshold, which we found to be incompatible with ab initio calculations. We perform ab initio simulations of crystalline and liquid carbon and aluminum over a wide range of densities and show that the computed band structure is in very good agreement with predictions from AVION.