[S-MP47_1PO1] Physics and Chemistry of Minerals

[SMP47-P01] Thermodynamic properties of Mg-postperovskite with Fe³⁺ and Al³⁺ dopant: an internally consistent LSDA+U study

*Xianlong WANG¹, Taku TSUCHIYA¹ (1.GRC, Ehime University and ELSI, Tokyo Institute of Technology)

Keywords:First-principles method, Internally consistent LSDA+U, Thermodynamic properties, Postperovskite

Thermodynamic properties of MgSiO₃ perovskite (Pv) and postperovskite (PPv) with Fe and Al incorporation at high pressure and high temperature are important to understand the Earth^,s lower mantle (LM). The thermodynamic properties of Fe²⁺, Fe³⁺, and Al³⁺-bearing Pv[1,2,3] and Fe²⁺-bearing PPv[4] have been investigated in our previous works uniformally based on first-principles method combined with the internally consistent LSDA+U method and quasi-harmonic approximation (QHA). However, to date, effects of trivalent ions, Fe³⁺ and Al³⁺, on the thermodynamic properties of PPv are still unclear. In this work, by using the same methods with previous works, the structural, electronic, magnetic, and thermodynamic properties of (Mg,Fe³⁺)(Si,Fe³⁺)O₃ and (Mg,Fe³⁺)(Si,Al³⁺)O₃ PPv at several pressures, from 0 GPa to 180 GPa, are investigated. Our results show that for (Mg,Fe³⁺)(Si,Fe³⁺)O₃ PPv, Fe³⁺ ions substituted at Mg and Si site respectively have the high and low spin state within the deep LM pressure range, while Fe³⁺ in (Mg,Fe³⁺)(Si,Al³⁺)O₃ PPv remains in the high spin state. Furthermore, separated phase between Fe₂O₃ and Al₂O₃ in PPv is found unfavorable.References:[1] Metsue, A. and Tsuchiya, T. (2012) Geophys. J. Int. 190, 310.[2] Tsuchiya, T. and Wang, X. (2013) J. Geophys. 118, 83.[3] Wang, X. and Tsuchiya, T. To be submitted.[4] Metsue, A. and Tsuchiya, T. (2011) J. Geophys. Res. 116, B08207.