Rh$_{2}$O$_{3}$(II)-type structures in Ga$_{2}$O$_{3}$ and In$_{2}$O$_{3}$ under high pressure: Experiment and theory
Hitoshi Yusa, Taku Tsuchiya, Nagayoshi Sata, and Yasuo Ohishi

High-pressure transitions of Ga$_{2}$O$_{3}$ and In$_{2}$O$_{3}$ were examined by using a laser-heated diamond-anvil cell combined with in-situ x-ray diffractometry at pressures up to 108 GPa and 20 GPa, respectively. To predict the transition pressure to high-pressure phases, first principles static lattice energy calculations based on the density functional theory were also performed. Rh$_{2}$O$_{3}$(II) phases were confirmed as post corundum phases for both Ga$_{2}$O$_{3}$ and In$_{2}$O$_{3}$ at about 37 GPa and 7 GPa, respectively. The transition pressures determined by high-pressure experiments are almost consistent with those by theoretical computations. In regard to the present sesquioxides, a link of transition from corundum to perovskite was not confirmed. The Rh$_{2}$O$_{3}$(II) phases converted to corundum phases under decompression at room temperature. The bulk modulus of Rh$_{2}$O$_{3}$(II) phase in Ga$_{2}$O$_{3}$ and In$_{2}$O$_{3}$ were determined as 271$\pm $10 GPa and 169$\pm $4 GPa with their pressure derivatives fixed at 4, respectively.

© 2008 The American Physical Society.