Structural and elastic properties of CaGeO3 perovskite at high pressures

A re-investigation on structural stability of CaGeO3 perovskite was conducted by synchrotron radiation X-ray diffraction with diamond anvil cell up to 48.8 GPa and first-principles calculations based on density functional theory. Both experimental and theoretical results reveal that CaGeO3 perovskite becomes more distorted deviated from the ideal perovskite with increasing pressure, in contradiction to previous experimental results. A phase transition from perovskite to post-perovskite of CaGeO3 is theoretically predicted to occur at 36–44 GPa, which is experimentally observed at 43 GPa quenched from high temperature. Elastic behavior of CaGeO3 at high pressures is similar to those of MgSiO3. A large positive jump (+4%) of shear velocity in CaGeO3 is predicted across the phase-transition pressure.