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 C₁₁ increases from 14.63×{}10¹¹ dyn/cm² to 14.70×{}10¹¹ dyn/cm² at 6 kbar. The values of C₃₃ and C₆₆ do not change with pressure to 6 kbar. These values are, respectively, 8.53±{}0.05 and 4.33±{}0.07×{}10¹¹ dyn/cm². The increases in the magnitude of C₁₃ and C₁₄ are nonlinear. The variation of C₄₄ shows a maximum between 3 and 4 kbar. The possible reasons for such a maximum are qualitatively discussed.