A nine-fold coordinated vanadium by oxygen in V<Subscript>2</Subscript>O<Subscript>3</Subscript> from first-principles calculations

Crystal structural stability of V<Subscript>2</Subscript>O<Subscript>3</Subscript> under high pressure has been investigated by first-principles calculations. Our results demonstrate that the phase-transition sequence of V<Subscript>2</Subscript>O<Subscript>3</Subscript> is from corundum structure to Gd<Subscript>2</Subscript>S<Subscript>3</Subscript>-type structure at 30 GPa, then to the Th<Subscript>2</Subscript>S<Subscript>3</Subscript>-type structure at 52 GPa, finally to the Os<Subscript>2</Subscript>Al<Subscript>3</Subscript>-type structure at 257 GPa. The latest Os<Subscript>2</Subscript>Al<Subscript>3</Subscript>-type structure with nine-fold coordinated cation is denser than previous reported models in sesquioxides, which is vibrationally stable at least at 329 GPa supported by its phonon spectrum. According to the contributions of different components to enthalpy, the Gd<Subscript>2</Subscript>S<Subscript>3</Subscript>-to-Th<Subscript>2</Sub script>S<Subscript>3</Subscript> and Th<Subscript>2</Subscript>S<Subscript>3</Subscript>-to-Os<Subscript>2</Sub script>Al<Subscript>3</Subscript> transitions are mainly caused by the volume contraction. Copyright EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2012