A Fully Ab-Initio Spin-Lattice Dynamics Framework for Magnetic Materials

TL;DR

This paper introduces a fully ab initio spin-lattice dynamics framework integrated into VASP, enabling parameter-free simulations of magnetic phenomena and providing data for machine learning potentials.

Contribution

It presents a novel, unified first-principles approach for coupled spin-lattice dynamics that does not rely on empirical parameters, validated across diverse magnetic materials.

Findings

Successfully recovers magnetic ground states from random initial conditions.

Provides physically correlated training data for magnetic machine-learning potentials.

Reduces energy MAE significantly when trained on randomized spin configurations.

Abstract

Coupled spin-lattice dynamics (SLD) underlie a wide range of magnetic phenomena, yet a unified first-principles framework that propagates both degrees of freedom without empirical parameterization has remained elusive. We present a fully ab initio SLD approach integrated into VASP, in which interatomic forces and effective magnetic fields are obtained at each time step from self-consistent constrained-moment density-functional calculations. The method is validated on four materials spanning ferromagnetic, non-collinear, and geometrically frustrated orders, recovering the correct magnetic ground state in every case from random initial conditions. SLD trajectories also provide physically correlated training data for magnetic machine-learning potentials, as demonstrated for BiFeO$_3$ by a reduction of up to approximately one order of magnitude in energy MAE over training on randomized spin configurations. This framework opens a practical first-principles route to finite-temperature spin-lattice coupled phenomena in magnetic materials.