Microscopic theory and quantum simulation of atomic heat transport

TL;DR

This paper develops a new method to simulate atomic heat transport using density-functional theory, overcoming previous limitations by exploiting gauge invariance, and validates it with simulations of liquid argon and heavy water.

Contribution

It introduces an expression for adiabatic energy flux within DFT, enabling ab-initio heat transport simulations despite quantum energy density ambiguities.

Findings

Method agrees with classical and non-equilibrium simulations for liquid argon.

Successfully applied to simulate heat transport in heavy water.

Shows gauge invariance ensures thermal conductivity is well-defined at atomic scale.

Abstract

Quantum simulation methods based on density-functional theory are currently deemed unfit to cope with atomic heat transport within the Green-Kubo formalism, because quantum-mechanical energy densities and currents are inherently ill-defined at the atomic scale. We show that, while this difficulty would also affect classical simulations, thermal conductivity is indeed insensitive to such ill-definedness by virtue of a sort of gauge invariance resulting from energy extensivity and conservation. Based on these findings, we derive an expression for the adiabatic energy flux from density-functional theory, which allows heat transport to be simulated using ab-initio equilibrium molecular dynamics. Our methodology is demonstrated by comparing its predictions with those of classical equilibrium and ab-initio non-equilibrium (M\"uller-Plathe) simulations for a liquid-Argon model, and finally applied to heavy water at ambient conditions.