Defects in hexagonal-AlN sheets by first-principles calculations E.F. de Almeida Junior, F. de Brito Mota, C.M.C. de Castilho, A. Kakanakova-Georgieva and G. K. Gueorguiev Eur. Phys. J. B, 85 1 (2012) 48 Published online: 30 January 2012 DOI: 10.1140/epjb/e2011-20538-6