Native point defects in Ti3GeC2 and Ti2GeC

Abstract

Using density functional theory, we calculated the formation energy of native point defects (vacancies, interstitials and antisites) in MAX phase Ti2GeC and Ti3GeC2 compounds. Ge vacancy with a formation energy of 2.87eV was the most stable defect in Ti2GeC while C vacancy with a formation energy of 2.47eV was the most stable defect in Ti3GeC2. Ge vacancies, in particular, were found to be strong phonon scattering centres that reduce the lattice contribution to thermal conductivity in Ti2GeC. In both compounds, the reported high thermal and electrical conductivity is attributed to the electronic contribution that originates from high density of states at the Fermi level.