Ab initio modeling of the formation and migration of monovacancies in Ti2AlC

We performed ab initio calculations for monovacancy formation and migration in Ti2AlC. Carbon and aluminum vacancies have almost equally low formation energies, respectively, at (Ti- and Al-rich) and (Ti- and C-rich) growth conditions, wherein both defects exhibit a high equilibrium concentration and structural tolerance to large off-stoichiometry in Ti2AlC. In contrast, VTi has the highest formation energy at all possible conditions. The intrinsic migration energies of various vacancies are determined to be in the sequence Em(VAl) < Em(VTi) < Em(VC).