Dynamical Exchange Interaction From Time-Dependent Spin Density Functional Theory

TL;DR

This paper introduces a first-principles method using time-dependent spin density functional theory to dynamically evaluate the Heisenberg exchange coupling in magnetic complexes, aligning well with traditional approaches.

Contribution

It presents a novel dynamical approach to determine the Heisenberg exchange constant from time-dependent spin density simulations, providing a first-principles alternative to existing methods.

Findings

The dynamical method yields exchange coupling values consistent with traditional schemes.

Time-dependent spin density evolution can be mapped onto classical Heisenberg models.

The approach offers a new way to analyze spin interactions in molecular complexes.

Abstract

We report on {\it ab initio} time-dependent spin dynamics simulations for a two-center magnetic molecular complex based on time-dependent non-collinear spin density functional theory. In particular, we discuss how the dynamical behavior of the {\it ab initio} spin-density in the time-domain can be mapped onto a model Hamiltonian based on the classical Heisenberg spin-spin interaction $J\vcr{S}_1\cdot \vcr{S}_2$. By analyzing individual localized-spin trajectories, extracted from the spin-density evolution, we demonstrate a novel method for evaluating the effective Heisenberg exchange coupling constant, $J$, from first principles simulations. We find that $J$, extracted in such a new dynamical way, agrees quantitatively to that calculated by the standard density functional theory broken-symmetry scheme.