Phase transition in MgSiO3 perovskite in the earth’s lower mantle
نویسندگان
چکیده
A new polymorph of MgSiO3 more stable than the Pbnm-perovskite phase has been identified by first-principles computations. It has the CaIrO3 structure with Cmcm symmetry and consists of SiO3 layers intercalated by eightfoldcoordinated Mg ions. High-temperature calculations within the quasiharmonic approximation give a volume change of f 1.5% and a Clapeyron slope of f 7.5F 0.3 MPa/K at f 2750 K and f 125 GPa. These pressure–temperature (P–T) conditions are close to those in which a phase transition in MgSiO3-perovskite has been observed by in situ angle dispersive X-ray diffraction measurements. This transition appears to be associated with the DU discontinuity. D 2004 Elsevier B.V. All rights reserved.
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