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First principles thermoelasticity of MgSiO 3 ‐perovskite: Consequences for the inferred properties of the lower mantle
Author(s) -
Karki Bijaya B.,
Wentzcovitch Renata M.,
de Gironcoli Stefano,
Baroni Stefano
Publication year - 2001
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 - 10.1029/2001gl012910
Subject(s) - adiabatic process , thermoelastic damping , mantle (geology) , grüneisen parameter , geology , thermodynamics , phonon , perovskite (structure) , moduli , geophysics , thermal , mineralogy , materials science , physics , condensed matter physics , chemistry , crystallography , quantum mechanics
Some key thermoelastic properties of MgSiO 3 ‐perovskite ( pv ) have been determined at lower mantle (LM) pressures and temperatures using the quasi‐harmonic approximation in conjunction with first principles phonon dispersions. The adiabatic bulk moduli ( K S ) of pv and of an assemblage of 80 vol% pv and 20 vol% MgO were obtained along the thermodynamically inferred adiabat and compared with the seismic counterpart given by the preliminary reference Earth model ( K PREM ). The discrepancy between calculated K S 's and K PREM in the deep LM suggests a super‐adiabatic gradient, or subtle changes of composition, or phase, or all beginning at about 1200 km. The Anderson Grüneisen parameter, δ S =(∂ln K S /∂lnρ) P , was predicted to decrease rapidly with depth (from 2.7 to 1.2 across the LM) supporting the thermal origin for the lateral heterogeneities throughout most of the LM.