Group Conductivity and Nonadiabatic Born Effective Charges of Disordered Metals, Warm Dense Matter, and Hot Dense Plasma

TL;DR

This paper introduces a method to determine ionization states in disordered metallic systems like warm dense matter and plasma by using nonadiabatic Born effective charges and group conductivity derived from first-principles calculations.

Contribution

It presents a novel approach to extract ionization states from group conductivity in disordered metals and plasma, extending the application of nonadiabatic Born effective charges.

Findings

Group conductivity can reveal ionization states in disordered systems.

NBEC differs from average ionization in static limit for metallic systems.

Method validated on various examples including aluminium and carbon WDM.

Abstract

The average ionization state is a critical parameter in plasma models for charged particle transport, equation of state, and optical response. The dynamical or nonadiabatic Born effective charge (NBEC), calculated via first principles time-dependent density functional theory, provides exact ionic partitioning of bulk electron response for both metallic and insulating materials. The NBEC can be trivially transformed into a ''group conductivity," that is, the electron conductivity ascribed to a subset of ions. We show that for disordered metallic systems, such as warm dense matter (WDM) and hot dense plasma, the static limit of the NBEC is different from the average ionization state, but that the ionization state can be extracted from the group conductivity even in mixed systems. We demonstrate this approach using a set of archetypical examples, including cold and warm aluminium, low- and high- density WDM carbon, and a WDM carbon-beryllium-hydrogen mixture.