Rh2O3(II)-type structures inGa2O3andIn2O3under high pressure: Experiment and theory

Abstract

High-pressure transitions of ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ and ${\mathrm{In}}_{2}{\mathrm{O}}_{3}$ were examined by using a laser-heated diamond-anvil cell combined with in situ x-ray diffractometry at pressures up to $108\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ and $20\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, 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. ${\mathrm{Rh}}_{2}{\mathrm{O}}_{3}(\mathrm{II})$ phases were confirmed as post corundum phases for both ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ and ${\mathrm{In}}_{2}{\mathrm{O}}_{3}$ at about $37\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ and $7\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, 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 ${\mathrm{Rh}}_{2}{\mathrm{O}}_{3}(\mathrm{II})$ phases converted to corundum phases under decompression at room temperature. The bulk modulus of ${\mathrm{Rh}}_{2}{\mathrm{O}}_{3}(\mathrm{II})$ phase in ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ and ${\mathrm{In}}_{2}{\mathrm{O}}_{3}$ were determined as $271\ifmmode\pm\else\textpm\fi{}10\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ and $169\ifmmode\pm\else\textpm\fi{}4\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ with their pressure derivatives fixed at 4, respectively.