The equilibrium structures of cubic, tetragonal and orthorhombic phases of magnesium silicate perovskite are found from first principles electronic structure calculations. Zone centre and zone boundary phonons of each phase are also calculated from ab initio forces from finite displacements, and phase transitions between the phases are analysed in terms of phonon instabilities, and coupling between modes. Both the cubic and tetragonal phases have strongly unstable modes dominated by rotation of the SiO 6 octahedra, which freeze in to ultimately form the orthorhombic phase. First principles molecular dynamics simulations at finite temperatures are used to further investigate the stability of the intermediate tetragonal phase and the coupling between participating phonon modes. The implications for a transition temperature between orthorhombic and tetragonal phases are discussed.
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October 01, 1998
Phase transitions in silicate perovskites from first principles
Michele C. Warren;
Michele C. Warren
University of Edinburgh, Department of Physics and Astronomy, Edinburgh, United Kingdom
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Michele C. Warren
University of Edinburgh, Department of Physics and Astronomy, Edinburgh, United Kingdom
Graeme J. Ackland
Bijaya B. Karki
Stewart J. Clark
Publisher: Mineralogical Society of Great Britain and Ireland
First Online:
03 Mar 2017
Online ISSN: 1471-8022
Print ISSN: 0026-461X
GeoRef, Copyright 2004, American Geological Institute.
American Geological Institute
Mineralogical Magazine (1998) 62 (5): 585–598.
Article history
First Online:
03 Mar 2017
Citation
Michele C. Warren, Graeme J. Ackland, Bijaya B. Karki, Stewart J. Clark; Phase transitions in silicate perovskites from first principles. Mineralogical Magazine 1998;; 62 (5): 585–598. doi:
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