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CaSiO 3 perovskite at lower mantle pressures
Author(s) -
Caracas R.,
Wentzcovitch R.,
Price G. David,
Brodholt J.
Publication year - 2005
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 - 10.1029/2004gl022144
Subject(s) - tetragonal crystal system , perovskite (structure) , orthorhombic crystal system , shear modulus , geology , bulk modulus , materials science , softening , mantle (geology) , phase (matter) , mineralogy , condensed matter physics , geophysics , crystal structure , crystallography , physics , composite material , chemistry , quantum mechanics
We investigate by first‐principles the structural behavior of CaSiO 3 perovskite up to lower mantle pressures. We confirm that the cubic perovskite modification is unstable at all pressures. The zero Kelvin structure is stabilized by SiO 6 octahedral rotations that lower the symmetry to tetragonal, orthorhombic, rhombohedral, or to a cubic supercell. The resulting structures have comparable energies and equation of state parameters. This suggests that relatively small deviatoric/shear stresses might induce phase transformations between these various structures softening some elastic moduli, primarily the shear modulus. The seismic signature accompanying a local increase in CaSiO 3 content should be a positive density anomaly and a negative V S anomaly.