Charge state and entropic effects affecting the formation and dynamics of divacancies in 3C-SiC

Using nudged elastic band calculations and first-principles molecular dynamics with enhanced sampling, we study the formation and dynamics of the divacancy VCVSi (VV) in cubic silicon carbide, including VV rotation and migration. We show that for all processes studied here the energy barriers and preferred pathway depend on the charge state of the defects. Our results indicate that the influence of multiple charge states and entropic effects should be considered for a quantitative description of the physical and dynamical properties of point defects at finite temperatures. In addition, we demonstrate that molecular dynamics simulations using machine-learning potentials can efficiently and reliably capture entropic effects and yield accurate free-energy barriers.