Noncollinear Magnetism in Density Functional Calculations

TL;DR

This paper extends density functional theory to handle noncollinear spin configurations, deriving new potential expressions and demonstrating their application on frustrated magnetic chromium clusters.

Contribution

It introduces a generalized formalism for noncollinear spin in density functional calculations, including derivation of exchange-correlation potential matrix elements.

Findings

Demonstrates noncollinear spin states in Cr clusters due to geometric frustration

Provides a generalized framework applicable to various functionals

Shows the importance of noncollinear treatment in magnetic systems

Abstract

We generalize the treatment of the electronic spin degrees of freedom in density functional calculations to the case where the spin vector variables employed in the definition of the energy functional can vary in any direction in space. The expression for the generalized exchange-correlation potential matrix elements is derived for general functionals which among their ingredients include the electron density, its gradient and Laplacian, the kinetic energy density, and non-local Hartree-Fock type exchange. We present calculations on planar Cr clusters that exhibit ground states with noncollinear spin densities due to geometrically frustrated antiferromagnetic interactions.