Gradient corrections to the exchange-correlation free energy

TL;DR

This paper introduces the first gradient correction to the exchange-correlation free energy for finite temperature density functional theory, improving accuracy without additional computational cost.

Contribution

It develops a new temperature-dependent extension for functionals beyond the local density approximation, enhancing finite temperature DFT calculations.

Findings

Finite temperature functionals outperform zero temperature ones in accuracy.

The proposed functionals match path integral Monte Carlo results for deuterium.

No additional computational cost is incurred by the new functionals.

Abstract

We develop the first order gradient correction to the exchange-correlation free energy of the homogeneous electron gas for use in finite temperature density functional calculations. Based on this we propose and implement a simple temperature dependent extension for functionals beyond the local density approximation. These finite temperature functionals show improvement over zero temperature functionals as compared to path integral Monte Carlo calculations for deuterium and perform without computational cost increase compared to zero temperature functionals and so should be used for finite temperature calculations.