Pressure Dependence of the Elastic Constants of SrTiO3

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Abstract
The effects of hydrostatic pressure between 0 and 22 kbar on the elastic constants of SrTiO3 were measured at 295°K. All constants increased linearly with pressure in this range. The pressure derivatives of the adiabatic constants dCij/dP are: 10.21±0.15, 3.51±0.15, and 1.24±0.05 for C11, C12, and C44, respectively. These pressure derivatives, in conjunction with the recent second‐harmonic generation results of Mackey and Arnold, allow us to determine the complete set of third‐order elastic constants. The results, in units of 1012 dyn/cm2, are: C111=−49.6±4.3, C112=−7.7±1.6, C123=+0.2±4.3, C144=−8.1±2.4, C166=−3.0±1.2, and C456=0.9±2.7. Combined with the temperature derivatives of the (second‐order) elastic constants at constant pressure, the pressure results allow a determination of the explicit volume and temperature dependences of these constants. In addition, the present results allow us to calculate the acoustic mode Grüneisen parameters, an approximate value of the limiting Grüneisen constant, γ0=1.52, and the coefficients of the polynominal and logarithmic (Murnaghan) forms of the high‐pressure equation of state of SrTiO3.