, Volume 17, Issue 3, pp 228-237

High-pressure crystal chemistry of MgSiO3 perovskite

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A high-pressure single-crystal x-ray diffraction study of perovskite-type MgSiO3 has been completed to 12.6 GPa. The compressibility of MgSiO3 perovskite is anisotropic with b approximately 23% less compressible than a or c which have similar compressibilities. The observed unit cell compression gives a bulk modulus of 254 GPa using a Birch-Murnaghan equation of state with K′ set equal to 4 and V/V 0 at room pressure equal to one. Between room pressure and 5 GPa, the primary response of the structure to pressure is compression of the Mg-O and Si-O bonds. Above 5 GPa, the SiO6 octahedra tilt, particularly in the [bc]-plane. The distortion of the MgO12 site increases under compression. The variation of the O(2)-O(2)-O(2) angles and bondlength distortion of the MgO12 site with pressure in MgSiO3 perovskite follow trends observed in GdFeO3type perovskites with increasing distortion. Such trends might be useful for predicting distortions in GdFeO3-type perovskites as a function of pressure.