Han Hsu

Thermoelasticity of Fe2+-bearing bridgmanite

We present local density approximation augmented by the Hubbard-type correction calculations of high-temperature elastic properties of bridgmanite with composition (Mg(1-x)Fex2+)SiO3 for 0 <= x <= 0.125. Results of elastic moduli and acoustic velocities for the Mg end-member (x=0) agree very well with the latest high-pressure and high-temperature experimental measurements. In the iron-bearing system, we focus particularly on the change in thermoelastic parameters across the state change that occurs in ferrous iron above similar to 30GPa, often attributed to a high-spin (HS) to intermediate-spin (IS) crossover but explained by first-principles calculations as a lateral displacement of substitutional iron in the perovskite cage. We show that the measured effect of this change on the equation of state of this system can be explained by the lateral displacement of substitutional iron and not by the HS to IS crossover. The calculated elastic properties of (Mg0.875Fe0.1252+)SiO3 along an adiabatic mantle geotherm somewhat overestimate longitudinal velocities but produce densities and shear velocities quite consistent with the Preliminary Reference Earth Model data throughout most of the lower mantle.

First-principles study of intermediate-spin ferrous iron in the Earth's lower mantle

Spin crossover of iron is of central importance in solid Earth geophysics. It impacts all physical properties of minerals that altogether constitute

Effects of aluminum on spin-state crossover of iron in the Earth's lower mantle

sim 95

Thermoelasticity of Fe 2+ -bearing bridgmanite

vol% of the Earths lower mantle: ferropericlase [(Mg,Fe)O] and Fe-bearing magnesium silicate (MgSiO

Effect of site degeneracies on the spin

_3

Thermoelasticity of (Mg,Fe)SiO

) perovskite. Despite great strides made in the past decade, the existence of intermediate-spin (IS) state in ferrous iron (Fe

_3

^{2+}

perovskite

) (with total electron spin

Intermediate-spin ferrous iron in the Earth's lower mantle?

S=1

Spin states and hyperfine interactions of iron incorporated in MgSiO

) and its possible role in the pressure-induced spin crossover in these lower-mantle minerals still remain controversial. Using density functional theory