Vice Professor ZHANG Zhigang and his team carry out extensive first principles molecular dynamics simulations to determine the equation of state, elastic constants, moduli and velocities of MgSiO3-perovskite over a wide temperature and pressure regime (from static conditions to 3500 K and from 36 GPa to 140 GPa). Systematic errors arising from approximations to the exchange–correlation functional in density functional theory are essentially eliminated with a generalized re-scaling method. Molecular dynamics trajectories were carefully converged with respect to duration and system size and analyzed to distinguish the effects of anharmonicity.
Based on the new elastic properties derived in this study, the pyrolite mineralogical model is found to predict wave velocities in close agreement with those of seismic observations in most of lower mantle regime.
Fig.1. Shear wave velocities of a six-component pyrolite model over the lower mantle regime along two adiabatic geotherms with potential temperatures of 1500 K according to present work and the thermodynamic model compared with PREM and AK135. (Image by ZHANG)
Zhang et al. Elastic properties of MgSiO3-perovskite under lower mantle conditions and the composition of the deep Earth. Earth and Planetary Science Letters, 2013, 379: 1-12 (Link)
