EOS Analysis of SiO₂ Polymorphs from Hugoniot Data

Abstract

Thermal analysis of the Hugoniot data of quartz was performed to discuss the equation of state (EOS) and phase transitions of stishovite, considering the changes in Grüneiisen parameter and internal energy due to phase transition. It was found that the effect of internal energy change was small, but the shock temperature and thermal pressure rather depended on the Grüneisen parameter. The derived isothermal compression curve of the high pressure phase was situated in the lower density region than those derived from the ultrasonic and Brillouin scattering data, and, at the pressures higher than 80-100 GPa, it was off towards the lower density region than the static X-ray data (room temperature).