Effect of hydrostatic pressure on the elastic constants ofV2O3

The elastic constants of pure single-crystal ${\mathrm{V}}_2$ ${\mathrm{O}}_3$ at 296 K are determined up to 4 kbar from measurements of the travel times of 30-MHz ultrasonic waves. Linear pressure dependences are found for all modes. Four elastic constants $C_{11}$, $C_{12}$, $C_{13}$, and $C_{33}$ have large positive pressure dependences. Comparison with results for $\alpha$-${\mathrm{Al}}_2$ ${\mathrm{O}}_3$ indicate that these large dependences are due in part to the highly anisotropic contraction of ${\mathrm{V}}_2$ ${\mathrm{O}}_3$ under pressure. The softening with pressure of the shear elastic stiffness $C_{\mathrm{ST}}$ suggests that a high-pressure transition occurs in ${\mathrm{V}}_2$ ${\mathrm{O}}_3$ between 150 and 250 kbar. Using the values and pressure dependences of $C_{11}$, $C_{12}$, $C_{13}$, and $C_{33}$, we calculate the changes in lattice parameters with pressure up to 140 kbar. Our results are compared with x-ray data of others.