First-principles study of spin transition and seismic properties of ferric iron-bearing post-perovskite with oxygen vacancy

摘要

The spin states, elastic properties and seismic velocities of ferric iron-bearing post-perovskite MgSiO3 (pPv) with single oxygen vacancy [Mg-8(Si-6,Fe-2)O-23 and Mg-16(Si-14,Fe-2)O-47] were calculated by first principles based on density functional theory. The effects of ferric iron and oxygen vacancy on seismic waves were studied for the host pPv subjected to a hydrostatic pressure. Calculations revealed a new spin transition from intermediate-spin to low-spin states with increasing pressure. As a result, the volume was reduced and the elastic constants were modified, producing a clear decrease in the seismic velocities of both compressive wave and shear wave due to the reduction of bulk modulus and shear modulus. The ferric iron and oxygen vacancy also had a minor effect on wave anisotropy.