DOSs of AlN nanosheets with single X substitution: (a) total DOS of Al₁₅ZnN₁₆, partial DOS of 2p states of a first neighboring N atom around Zn atom and 3d states of a Zn atom, (b) total DOS of Al₁₅CdN₁₆, partial DOS of 2p states of a first neighboring N atom around Cd atom and 4d states of a Cd atom, respectively. Fermi energy is indicated by the dashed vertical line.