"Ab initio theory of native defects in alloys: application to charged N vacancies in Al_x Ga _1-x N alloys",
L.E. Ramos, J. Furthmüller, F. Bechstedt, L.M.R. Scolfaro, and J.R. Leite,
J. Phys. C: Condens. Matt. 14 , 2577 (2001).

We present calculations of the electronic and atomic structures of neutral and charged nitrogen vacancies in AlxGa1-xN alloys using a combination of first-principles methods. The treatment of the alloys is based on the generalized quasichemical approach to disorder and composition effects and a cluster expansion to account for the various configurations. The point defects are modeled by supercells which are multiples of the clusters. The total energy and electronic-structure calculations are performed within the density functional theory and the local spin density approximation. We study the atomic structure, the energetics and the charge-dependent vacancy states for the different clusters versus cation numbers and for the alloys versus composition x.