An interpretation of the structures of mantle minerals at high pressure in terms of interionic forces

抄録

The energy minimization program WMIN of BUSING (1970) has been applied to predict the crystal structures of mantle minerals at high pressure. The repulsive parameters, ionic radius A_i and softness parameter B_i (ionic compressibility) to be used in the predictions are evaluated for Mg²⁺, Si⁴⁺, Al³⁺, Ca²⁺, Fe²⁺ and O^2- ions by employing the cell dimensions and atomic coordinates of α-Mg₂SiO₄(olivine), Fe₂SiO₄ (fayalite), MgAl₂O₄(spinel) and CaMgSi₂O₆(diopside) determined at one atm. These parameters were then used to predict the u-parameter of γ-Mg₂SiO₄(spinel) by the energy minimization method of WMIN. The u-parameter, 0.3685 was obtained for the observed cell parameter a(=8.0649A). The method and the parameters will be applied to predict other stable minerals in Earth's mantle.