Ultrasonic measurements of single-crystal gold under hydrostatic pressures up to 8 GPa in a Kawai-type multi-anvil apparatus

Ultrasonic measurements were conducted on single-crystal gold at ambient condition and hydrostatic pressures up to 8 GPa at room temperature in a Kawai-type multi-anvil apparatus. The P-wave velocities measured at high pressures were in good agreement with Daniels and Smith's ultrasonic study. The three independent elastic constants of gold at ambient condition were determined to be C ₁₁=192.7 GPa, C ₁₂=162.9 GPa, and _{C 44}=42.4 GPa. On the basis of an analysis of previous elastic data and the present ultrasonic data, the pressure derivatives of three elastic constants were estimated to be C₁₁ = 7.12, C₁₂ = 6.24, and C₄₄ = 1.82. The calculated values of isothermal bulk modulus (K _T0) and its pressure derivatives (K′_T0) are K _T0 = 166.44 GPa and K′_T0 = 6.56. This indicates that Anderson et al.'s model of equation of state of gold might underestimates pressure about 1 GPa at pressure around 23 GPa and ambient temperature. Our results explained the discrepancies among the models of equation of state of gold proposed previously.