Exchange torque in noncollinear spin density functional theory with a semilocal exchange functional

TL;DR

This paper introduces a new semilocal exchange-correlation functional for noncollinear spin density functional theory that is gauge invariant and capable of capturing exchange-correlation torques, with promising results on chromium clusters.

Contribution

The authors develop a novel semilocal functional explicitly designed for noncollinear magnetism, incorporating gauge invariance and exchange-correlation torques, improving computational efficiency.

Findings

Functional performs favorably compared to more expensive methods

Successfully captures exchange-correlation torques in noncollinear systems

Demonstrates effectiveness on frustrated antiferromagnetic chromium clusters

Abstract

We present a semilocal exchange-correlation energy functional for noncollinear spin density functional theory based on short-range expansions of the spin-resolved exchange hole and the two-body density matrix. Our functional is explicitly derived for noncollinear magnetism, U(1) and SU(2) gauge invariant, and gives rise to nonvanishing exchange-correlation torques. Testing the functional for frustrated antiferromagnetic chromium clusters, the exchange part is shown to perform favorably compared to the far more expensive Slater and optimized effective potentials, and a delicate interplay between exchange and correlation torques is uncovered.