DFT calculations were performed with the AM05 XC functional to determine the structural parameters of the ten polymorphs under consideration. We investigated five polymorphs of Ga 2 O 3 : the α phase 20 (rhombohedral corundum), the stable β phase (base-centered monoclinic), the γ phase (cubic defective spinel-type), the δ phase 64 (cubic bixbyite), and the κ phase . For the In 2 O 3 , we also studied the α phase 20 (rhombohedral corundum), the cubic bixbyite δ phase, and three different orthorhombic phases, labeled as ω1, ω2, and ω3. The atomic geometries are illustrated in Fig. .