Crystal morphology and surface structures of orthorhombic MgSiO3 perovskite |
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| Authors: | M Alfredsson J P Brodholt D P Dobson A R Oganov C R A Catlow S C Parker G D Price |
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| Institution: | (1) Davy Faraday Research Laboratory, The Royal Institution of Great Britain, 21 Albemarle Street, London, W1S 4BS, UK;(2) Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, UK;(3) Laboratory of Crystallography, Department of Materials, ETH Zurich, CH-8092 Zurich, Switzerland;(4) Department of Chemistry, Bath University, Bath, BA2 7AY, UK |
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| Abstract: | Orthorhombic MgSiO3 perovskite is thought to be the most abundant mineral in the mantle of the Earth. Its bulk properties have been widely studied, but many geophysical and rheological processes are also likely to depend upon its surface and grain boundary properties. As a first step towards modelling these geophysical properties, we present here an investigation of the structures and energetics of the surfaces of MgSiO3-perovskite, employing both shell-model atomistic effective-potential simulations, and density-functional-theory (DFT) calculations. Our shell-model calculations predict the {001} surfaces to be the energetically most stable surfaces: the calculated value of the surface energy being 2.2 J/m2 for the MgO-terminated surface, which is favoured over the SiO2-terminated surface (2.7 J/m2). Also for the polar surfaces {111}, {101} and {011} the MgO-terminated surfaces are energetically more stable than the Si-terminated surfaces. In addition we report the predicted morphology of the MgSiO3 perovskite structure, which is dominated by the energetically most stable {001} and {110} surfaces, and which appears to agree well with the shape of grown single crystals. |
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| Keywords: | Perovskite Morpholgy Surface structures Grain boundary Mantle Modelling |
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