Thermal density functional theory: Time-dependent linear response and approximate functionals from the fluctuation-dissipation theorem

TL;DR

This paper extends time-dependent density functional theory to finite temperatures using the fluctuation-dissipation theorem, enabling the development of new thermal exchange-correlation functionals for improved modeling of thermal systems.

Contribution

It generalizes the van Leeuwen proof of TDDFT to thermal ensembles, allowing finite-temperature extensions of key relations and the creation of new thermal XC approximations.

Findings

Generalized the van Leeuwen proof to thermal ensembles

Extended the Gross-Kohn relation to finite temperatures

Provided a framework for new thermal XC functionals

Abstract

The van Leeuwen proof of linear-response time-dependent density functional theory (TDDFT) is generalized to thermal ensembles. This allows generalization to finite temperatures of the Gross-Kohn relation, the exchange-correlation kernel of TDDFT, and fluctuation dissipation theorem for DFT. This produces a natural method for generating new thermal exchange-correlation (XC) approximations.