The elastic constants of cassiterite SnO2 and their pressure and temperature dependence

The second-order elastic constants of single-crystal cassiterite, rutile structure SnO2, have been measured as functions of pressure (1 bar to 10 kbar) and temperature 25°–100°C) by using the pulse superposition method. The observed negative pressure derivative and positive temperature derivative of Cs = ½(C11 - C12) are in qualitative agreement with those measured for isostructural TiO2 [Manghnani, 1969] and GeO2 [Wang and Simmons, 1973]. According to the VRH averaging scheme the pertinent isotropic bulk elastic properties are K0S = 2.123 Mbar, (∂Ks/∂P)T = 5.50, and (∂Ks/∂T)P = −0.18 kbar/°C. The calculated bulk modulus K0s of cassiterite is related systematically to the corresponding data for TiO2 and GeO2 with respect to cation radius; however, the pressure and temperature derivatives of K0s for SnO2 are significantly lower and higher, respectively, than those of the rutile structure analogues.