Crystal morphology and surface structures of orthorhombic MgSiO ₃ perovskite

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• 作者：M. Alfredsson ; J. P. Brodholt ; D. P. Dobson ; A. R. Oganov ; C. R. A. Catlow ; S. C. Parker and G. D. Price
• 关键词：Perovskite ; Morpholgy ; Surface structures ; Grain boundary ; Mantle ; Modelling
• 刊名：Physics and Chemistry of Minerals
• 出版年：2005
• 出版时间：February 2005
• 年：2005
• 卷：31
• 期：10
• 页码：671-682
• 全文大小：669 KB

文摘

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.