Nature of Non-Adiabatic Electron-Ion Forces in Liquid Metals

TL;DR

This paper investigates the non-adiabatic electron-ion forces in liquid metals and warm dense plasmas, revealing complex frictional interactions driven by electronic excitations affecting ionic dynamics.

Contribution

It provides detailed ab-initio calculations of the full friction tensor, highlighting the inhomogeneous, anisotropic, and non-diagonal nature of electron-ion interactions in liquid metals.

Findings

Friction forces are significant between nearest neighbors.

Electron-ion interactions cause hydrodynamic couplings.

Friction tensor varies with density and is inhomogeneous.

Abstract

An accurate description of electron-ion interactions in materials is crucial for our understanding of their equilibrium and non-equilibrium properties. Here, we assess the properties of frictional forces experienced by ions in non-crystalline metallic systems, including liquid metals and warm dense plasmas, that arise from electronic excitations driven by the nuclear motion due to the presence of a continuum of low-lying electronic states. To this end, we perform detailed ab-initio calculations of the full friction tensor that characterizes the set of friction forces. The nonadiabatic electron-ion interactions introduce hydrodynamic couplings between the ionic degrees of freedom, which are sizeable between nearest neigbors. The friction tensor is generally inhomogeneous, anisotropic and non-diagonal, especially at lower densities.