Magnetostriction and Long-Range Interactions in Coupled Spin and Lattice Dynamics

A scalable and symplectic algorithm for coupled spin dynamics and molecular dynamics was
recently released in the molecular dynamics code LAMMPS. Our presentation will focus on two
of its recent improvements: (1) incorporating magnetostrictive effects in and (2) implementing
scalable techniques to compute long-range magnetic interactions.
A methodology accounting for magnetostriction in hexagonal crystals based on Néel’s work on
pair anisotropy models was developed and applied to HCP-cobalt. We parametrized our model
using ab-initio calculations within the Spin-Dependent Density Functional Theory framework in-
cluding the Spin-Orbit coupling. We will show how typical magnetostrictive results were recovered.
Although negligible for most small magnetic simulations, the magnetic dipolar energy becomes
fundamental for larger configurations, where magnetic domains can nucleate and be stabilized. In
order to account for it (and for the associated magneto-mechanical interactions), two methodolo-
gies, Ewald sums and Particle-Particle Particle-Mesh, were coupled to the spin-lattice symplectic
algorithms developed in LAMMPS. Scaling and energy preservation results will be presented.