High-pressure behaviour of orthorhombic MgSiO3 perovskite crystal is simulated by using the density functional theory and plane-wave pseudopotentials approach up to 120 GPa pressure at zero temperature. The lattice co...High-pressure behaviour of orthorhombic MgSiO3 perovskite crystal is simulated by using the density functional theory and plane-wave pseudopotentials approach up to 120 GPa pressure at zero temperature. The lattice constants and mass density of the MgSiO3 crystal as functions of pressure are computed, and the corresponding bulk modulus and bulk velocity are evaluated. Our theoretical results agree well with the high-pressure experimental data. A thermodynamic method is introduced to correct the temperature effect on the O-K first-principles results of bulk wave velocity, bulk modulus and mass density in lower mantle PIT range. Taking into account the temperature corrections, the corrected mass density, bulk modulus and bulk wave velocity of MgSiO3-perovskite are estimated from the first-principles results to be 2%, 4%, and 1% lower than the preliminary reference Earth model （PREM） profile, respectively, supporting the possibility of a pure perovskite lower mantle model.展开更多
We report new shock-compression data for polycrystalline （Mg,Fe）O up to 130 GPa shock pressures corresponding to Earth＇s lowermost mantle conditions. Our data together with the existing shock-wave data of （Mg, Fe...We report new shock-compression data for polycrystalline （Mg,Fe）O up to 130 GPa shock pressures corresponding to Earth＇s lowermost mantle conditions. Our data together with the existing shock-wave data of （Mg, Fe）O and its end-members MgO and FeO reveal that the Hugoniot curves of （Mg,Fe）O does not change with varying FeO content for their B1 phase （NaCl-structure） in the pressure-relative-volume plane. The evidence of the volume change within 3% at around 120GPa along the Hugoniot of （Mgo.6, Feo.4）O is consistent with a structural transition from B1 phase （NaC1 cubic） to B8 phase （NiAs-type hexagonal）. Such a structural transition of （Mg, Fe）O, if indeed occurs, may in part contribute to the scattering of seismic waves and change in velocity gradient found in the lowermost mantle.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 40474033 and 10376024, and the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No 20050613017.
文摘High-pressure behaviour of orthorhombic MgSiO3 perovskite crystal is simulated by using the density functional theory and plane-wave pseudopotentials approach up to 120 GPa pressure at zero temperature. The lattice constants and mass density of the MgSiO3 crystal as functions of pressure are computed, and the corresponding bulk modulus and bulk velocity are evaluated. Our theoretical results agree well with the high-pressure experimental data. A thermodynamic method is introduced to correct the temperature effect on the O-K first-principles results of bulk wave velocity, bulk modulus and mass density in lower mantle PIT range. Taking into account the temperature corrections, the corrected mass density, bulk modulus and bulk wave velocity of MgSiO3-perovskite are estimated from the first-principles results to be 2%, 4%, and 1% lower than the preliminary reference Earth model （PREM） profile, respectively, supporting the possibility of a pure perovskite lower mantle model.
基金Supported by the National Natural Science Foundation of China under Grant No 40474033, and the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No 20050613017.
文摘We report new shock-compression data for polycrystalline （Mg,Fe）O up to 130 GPa shock pressures corresponding to Earth＇s lowermost mantle conditions. Our data together with the existing shock-wave data of （Mg, Fe）O and its end-members MgO and FeO reveal that the Hugoniot curves of （Mg,Fe）O does not change with varying FeO content for their B1 phase （NaCl-structure） in the pressure-relative-volume plane. The evidence of the volume change within 3% at around 120GPa along the Hugoniot of （Mgo.6, Feo.4）O is consistent with a structural transition from B1 phase （NaC1 cubic） to B8 phase （NiAs-type hexagonal）. Such a structural transition of （Mg, Fe）O, if indeed occurs, may in part contribute to the scattering of seismic waves and change in velocity gradient found in the lowermost mantle.
