Anion ordering in spinel-type gallium oxonitride

The specific locations of the anions-nitrogen and oxygen-in the crystallographic sites are not known in the spinel-type gallium oxonitride. We report here on an indirect method for determining the specific location of the light elements N and O in a defect spinel-structured gallium oxonitride, Ga2.79O3.05N0.76. The locations of elements that are adjacent in the periodic table (Delta Z=±1) are indistinguishable with conventional x-ray diffraction techniques. However, by examining the local electronic structure we show that the anions are spatially ordered such that R3¯ m (no. 166) is the most appropriate defect-free space group. Finally, we determined the electronic band gap of Ga2.79O3.05N0.76 experimentally to be 2.95 ± 0.30, agreeing with our calculated value of 2.79 eV (direct) for Ga3O3N using a local density approximation functional including a semilocal potential modified from that of Becke and Johnson (the MBJLDA functional).