Pressure Dependence of the Elastic Constants of Calcite

The values of the six elastic constants of single-crystal calcite are determined to 6 kbar at 25°C by the pulse-echo method. The values of these constants at 1 atm and 25°C agree fairly well with those obtained by Peselnick and Robie. The value of $C_{11}$ increases from 14.63×${10}^{11}$ dyn/${\mathrm{cm}}^2$ to 14.70×${10}^{11}$ dyn/${\mathrm{cm}}^2$ at 6 kbar. The values of $C_{33}$ and $C_{66}$ do not change with pressure to 6 kbar. These values are, respectively, 8.53±0.05 and 4.33±0.07×${10}^{11}$ dyn/${\mathrm{cm}}^2$. The increases in the magnitude of $C_{13}$ and $C_{14}$ are nonlinear. The variation of $C_{44}$ shows a maximum between 3 and 4 kbar. The possible reasons for such a maximum are qualitatively discussed.