First-Principles Calculation of Principal Hugoniot and K-Shell X-ray Absorption Spectra for Warm Dense KCl

TL;DR

This paper uses first-principles molecular dynamics to calculate the principal Hugoniot and K-shell X-ray absorption spectra of warm dense KCl, revealing electronic structure evolution and factors affecting pressure and ionization.

Contribution

It provides a detailed first-principles analysis of electronic structures and ionization effects in warm dense KCl under shock conditions, including pressure and spectral properties.

Findings

Pressure ionization occurs at lower energy levels for Cl and K 3p electrons.

Band gap persists after pressure ionization, influencing electronic structure evolution.

Cancellation between electronic kinetic and virial pressures reduces deviation in Hugoniot.

Abstract

Principal Hugoniot and K-shell X-ray absorption spectra of warm dense KCl are calculated using the first-principles molecular dynamics method. Evolution of electronic structures as well as the influence of the approximate description of ionization on pressure (caused by the underestimation of the energy gap between conduction bands and valence bands) in the first-principles method are illustrated by the calculation. Pressure ionization and thermal smearing are shown as the major factors to prevent the deviation of pressure from global accumulation along the Hugoniot. In addition, cancellation between electronic kinetic pressure and virial pressure further reduces the deviation. The calculation of X-ray absorption spectra shows that the band gap of KCl persists after the pressure ionization of the $3p$ electrons of Cl and K taking place at lower energy, which provides a detailed understanding to the evolution of electronic structures of warm dense matter.