Elasticity of AlFeO(3) and FeAlO(3) perovskite and post-perovskite from first-principles calculations

Razvan Caracas (1)

1 LST - Laboratoire de Sciences de la Terre

We use state-of-the-art ab initio calculations based on the generalized gradient approximation of the density functional theory in the planar augmented wavefunction formalism to determine the elastic constants tensor of perovskite and post-perovskite with formulas AlFeO(3) and FeAlO(3) in which Fe or Al respectively occupy only octahedral sites, for the stable magnetic configurations. The phase transition between perovskite and post-perovskite is associated with a site exchange, during which Fe from the inter-octahedral site in perovskite moves into the octahedral site in post-perovskite. Following this transition path the elastic moduli show positive jumps, considerably larger than for MgSiO(3). The phase transition is marked by a positive jump of 0.04 km/s (0.33\%) in the velocity of the compressional waves and by a negative jump of -0.15 km/s (-1.87\%) in shear wave velocity. We find that the effects of the Mg + Si <=> Al + Fe substitution on the seismic properties of MgSiO(3) perovskite and post-perovskite depend on the crystallography of the substitution, namely the position the exchanged cations take in the structure. Citation: Caracas, R. (2010), Elasticity of AlFeO(3) and FeAlO(3) perovskite and post-perovskite from first-principles calculations, Geophys. Res. Lett., 37, L20306, doi:10.1029/2010GL044404.

Mots clés: LOWER MANTLE; PHASE; MGSIO3; PRESSURE; DYNAMIC S; IRON

Domaines: Sciences de la Terre

Razvan Caracas. Elasticity of AlFeO(3) and FeAlO(3) perovskite and post-perovskite from first-principles calculations. Geophysical Research Letters, 2010, 37, pp.L20306. ⟨10.1029/2010GL044404⟩. ⟨hal-00676913⟩