Pressure-induced spin transitions of iron in MgSiO3 perovskite: a GGA+U study

Abstract

First-principles calculations using the GGA+U method have been made to investigate the spin transitions of iron in MgSiO3 perovskite up to 120 GPa, with Fe2+ and Fe3+ at the A and B sites involving different substitution mechanisms and various charge compensation configurations. Our results, unlike those from previous local density approximation and generalized gradient approximation calculations, are now consistent with available experimental data for the spin states of Fe3+ in perovskite. In particular, our calculations show that both Fe2+ and Fe3+ at the A site do not exhibit any spin transition at the lower mantle conditions. However, Fe3+ at the B site in both (Mg0.9375Al0.0625)(Si0.9375Fe0.0625)O3 and (Mg0.9375Fe0.0625)(Si0.9375Fe0.0625)O3 undergoes a high-spin to low-spin transition at ∼ 35 GPa, and this spin-transition pressure is largely independent on substitution mechanisms and charge compensation configurations.