Elastic Properties of SiO2 Stishovite to 50GPa

Stishovite is a major phase in the crustal portion of subducted slabs in the bottom of the upper amntle and in the lower mantle. We have measured the acoustic velocities, densities, and Raman frequencies of pure SiO2 stishovite at pressures up to 50 GPa. The acoustic velocities data were used to calculate single-crystal and aggregate elastic moduli for stishovite. For single-crystal elastic moduli we obtained: C11 = 462(3) GPa, C33 = 769(5) GPa, C44 = 258(2) GPa, C66 = 299(3) GPa, C12 = 201(2) GPa, C13 = 190(2) GPa. Aggregate elastic moduli were fit at values: KS0 = 313(3) GPa, K0' = 4.41(20); G0 = 226(2) GPa. Our data are in excellent agreement with previous ambient and low-pressure measurements performed with Brillouin scattering (Weidner et al., 1982) and with first principles calculations ( Karki et al., 1997), The shear modulus varies strongly as a function of pressure. Our high-pressure measurements on variation of elastic properties with increasing pressure are in excellent agreement with the Landau theory calculations (Carpenter et al., 2000) which predict the high-pressure elastic properties in vicinity of second-order phase transitions. There is also reasonagle agreement with than the predicted high-pressure behavior fromfirst-principles methods.