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Comparison between the lattice dynamics and molecular dynamics methods: Calculation results for MgSiO3 perovskite

Matsui, M; Price, GD; Patel, A; (1994) Comparison between the lattice dynamics and molecular dynamics methods: Calculation results for MgSiO3 perovskite. Geophysical Research Letters , 21 (15) 1659 - 1662. 10.1029/94GL01370. Green open access

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Abstract

The lattice dynamics (LD) and molecular dynamics (MD) methods have been used to calculate the structure, bulk modulus, and volume thermal expansivity of MgSiO3 perovskite, in order to investigate the reliability of the two simulation techniques over a wide range of temperature and pressure conditions. At an intermediate temperature of 500 K and zero pressure, the LD and MD values are in exellent agreement for both the structure and bulk modulus of MgSiO3 perovskite. At high temperatures and zero pressure, however, the LD method, which is based on the quasi-harmonic approximation, increasingly overestimates the molar volume of MgSiO3 perovskite because of the neglect of higher-order anharmonic terms. At the high temperatures and high pressures prevailing in the lower mantle, the errors in the LD values for both the molar volume and bulk modulus, relative to the MD values, are generally small or negligible. However, since anharmonicity decreases substantially with pressure but increases rapidly with temperature, the error in the LD simulated volume thermal expansivity is serious, especially in the lower pressure region.

Type: Article
Title: Comparison between the lattice dynamics and molecular dynamics methods: Calculation results for MgSiO3 perovskite
Open access status: An open access version is available from UCL Discovery
DOI: 10.1029/94GL01370
Publisher version: http://dx.doi.org/10.1029/94GL01370
Language: English
Additional information: Copyright 1994 by the American Geophysical Union
Keywords: Computer-simulation, Mantle, Temperature, Polymorphs, Crystal, State
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > VP: Research
URI: https://discovery.ucl.ac.uk/id/eprint/99100
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