Theoretical study of nitrogen vacancies in Ti_4AIN_3

摘要

We have investigated the energetics of the N vacancy formation in Ti_4AlN_3 by ab initio calculations. We identify N 2a sites (Wyckoff notation) in Ti_4AlN__(2.75) as the most probable vacancy sites based on the energetics of vacancy formation. Furthermore, Ti_4AlN_3 does not exhibit any states at the Fermi level. Introducing N vacancies causes states to appear at the Fermi level, which may enable electron transport. Recently measured conductivity data [Finkel et al., Phys. Rev. B 67, 235108 (2003)] for Ti_4AlN_3 can be understood based on our calculations.