Equation of state of stishovite and interpretation of SiO2 shock-compression data -: art. no. 2015

We present an isothermal equation of state for the high-pressure stishovite phase of SiO2 based on synchrotron X-ray diffraction at 300 K to 60 GPa. The inferred equation of state is the same for stishovite synthesized from pure SiO2 glass as from a natural, basalt glass that forms stishovite in association with other mineral phases, yielding a zero-pressure bulk modulus K-0T = 312.9(+/-3.4) GPa and pressure derivative K-0' = 4. 8(+/-0.2). Our measurements of stishovite at static, high pressures predict a shock-compressed (Hugoniot) state that is 2.4 (+/-1.6)% denser than observed for SiO2, suggesting that an amorphous phase, rather than stishovite, is produced under impact loading.