# First-Principles Simulations of Warm Dense Lithium Fluoride

## TL;DR

This study uses first-principles simulations to investigate the properties of warm dense lithium fluoride, revealing ionization effects, benchmarking EOS models, and analyzing electronic structure at extreme conditions.

## Contribution

It provides comprehensive first-principles data on LiF's behavior in warm dense matter states, including ionization features and electronic properties, serving as benchmarks for EOS models.

## Key findings

- Identified compression maximum and shoulder on Hugoniot curve due to shell ionization.
- Provided benchmark data for EOS tables like SESAME, LEOS.
- Observed that the electronic gap can remain open at high densities and temperatures.

## Abstract

We perform first-principles path integral Monte Carlo (PIMC) and density functional theory molecular dynamics (DFT-MD) calculations to explore warm dense matter states of LiF. Our simulations cover a wide density-temperature range of $2.08-15.70$~g$\,$cm$^{-3}$ and $10^4-10^9$~K. Since PIMC and DFT-MD accurately treat effects of atomic shell structure, we find a pronounced compression maximum and a shoulder on the principal Hugoniot curve attributed to K-shell and L-shell ionization. The results provide a benchmark for widely-used EOS tables, such as SESAME, LEOS, and models. In addition, we compute pair-correlation functions that reveal an evolving plasma structure and ionization process that is driven by thermal and pressure ionization. Finally, we compute electronic density of states of liquid LiF from DFT-MD simulations and find that the electronic gap can remain open with increasing density and temperature to at least 15.7 g$~$cm$^{-3}$.