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Theoretical Study of the stability of MgSiO 3 ‐perovskite in the deep mantle
Author(s) -
Dubrovinsky L.,
Saxena S. K.,
Ahuja R.,
Johansson B.
Publication year - 1998
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/1998gl900141
Subject(s) - stishovite , periclase , anharmonicity , perovskite (structure) , silicate perovskite , thermodynamics , gibbs free energy , materials science , oxide , mineralogy , mantle (geology) , geology , high pressure , condensed matter physics , chemistry , geophysics , crystallography , physics , spinel , metallurgy
We have used theoretical methods (Full‐Potential Linear‐muffin‐tin‐orbital, FPLMTO, and lattice dynamics) to calculate the Gibbs free energy of the phases, perovskite (MgSiO 3 ), SBAD (SiO 2 ), stishovite (SiO 2 ) and periclase (MgO). At 300 K, perovskite is found to be stable at all pressures up to 150 GPa. As the temperature is increased, the free energy difference between the oxide mixture and perovskite decreases and at 3000 K and at pressures between 105 and 115 GPa, the oxide mixture becomes more stable. The calculated equilibrium pressure is much higher than the observed experimental pressure which may be due to stress in the sample and/or due to the inadequacy of the applied theoretical models not accounting for anharmonicity effects.