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Lattice Thermal Conductivity of MgSiO 3 Postperovskite Under the Lowermost Mantle Conditions From Ab Initio Anharmonic Lattice Dynamics
Author(s) -
Dekura Haruhiko,
Tsuchiya Taku
Publication year - 2019
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 - 10.1029/2019gl085273
Subject(s) - anharmonicity , anisotropy , thermal conductivity , mantle (geology) , isotropy , materials science , phonon , core–mantle boundary , geology , condensed matter physics , mineralogy , seismic anisotropy , lattice (music) , geophysics , physics , optics , composite material , acoustics
Abstract The lattice thermal conductivity ( κ lat ) of MgSiO 3 postperovskite (Mg‐PPv) under the lowermost mantle pressure ( P ) and temperature ( T ) conditions was calculated using density functional theory combining anharmonic lattice dynamics theory. The κ lat of Mg‐PPv was found to be ~50% higher than that of MgSiO 3 bridgmanite (Mg‐Brg) owing to the larger phonon group velocity and lifetime. The lateral variation in the core‐mantle boundary heat flux ( q CMB ) can be enhanced by the Brg‐PPv phase transition. We also found that the κ lat along the c axis of Mg‐PPv is close to the conductivity of isotropic aggregate. This suggests that the effect of anisotropy in the κ lat on q CMB would be minor if the transversely isotropic aggregate with the c axis vertical alignment, a potential source of seismic anisotropy in the D″ layer, is developed.