Vacancy-cluster mechanism of metal-atom diffusion in substoichiometric carbides

We find, using ab initio atomistic simulations of vacancy-mediated diffusion processes in TiC and ZrC, that a multivacancy self-diffusion mechanism is operative for metal-atom diffusion in substoichiometric carbides. It involves a special type of a stable point defect, a metal vacancy dressed in a shell of carbon vacancies. We show that this vacancy cluster is strongly bound and can propagate through the lattice without dissociating. DOI: 10.1103/PhysRevB.87.054203