Minimum direct two-body barrier approach for kinetic Monte Carlo simulations: a unified framework for bulk diffusion and surface growth

Abstract

Kinetic Monte Carlo (KMC) simulations are widely used to investigate diffusionmediated processes that unfold on time scales inaccessible to molecular dynamics.However, conventional atomistic KMC requires extensive activation-barriercatalogues—especially in multicomponent systems where local environments inducestrong many-body effects. Here, we introduce the minimum Direct Two-Body Barrier(mDTBB) approach, a compact strategy in which the activation energy barrier for agiven event is defined as the minimum energy among its relevant two-bodyinteractions. This substantially reduces the number of required barriers while retainingthe essential physics associated with saddle-point energetics. We validate mDTBBapproach using two well-established test cases: (i) vacancy mediated solute clusteringin supersaturated Al–Mg–Cu alloys, and (ii) surface diffusion during Au deposition onTiO2 (110). In both systems, the simulation trends closely reproduce experimentalobservations, and the resulting energetics are consistent with those obtained fromsignificantly more computationally demanding methods. We further apply mDTBB in apredictive setting to Ga monolayer formation on GaN, demonstrating its ability todeliver physically grounded insights in regimes where experimental data are scarce.Overall, mDTBB emerges as a versatile and computationally efficient framework formodeling bulk and surface atomistic processes without the need for extensive barrier parametrisation.