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Abstract: We investigate by first-principles calculations the effect of ferrous iron, Fe2+, on the structure and the equation of state of MgSiO3 post-perovskite. We find that ferrous iron is high-spin over the pressure range of the mantle assuming a ferromagnetic structure. The bulk modulus and the specific volume increase with the addition of ferrous iron to MgSiO3. We find that Fe partitions preferentially to post-perovskite and broadens the two-phase pressure range. [Copyright &y& Elsevier]

Using a first-principles based, magnetic tight-binding total energy model, the magnetization energy and moments are computed for various ordered spin configurations in the high pressure polymorphs of iron (fcc, or γ-Fe, and hcp, or ε-Fe), as well as ferromagnetic bcc iron (α-Fe). For hcp an antiferromagnetic spin configuration is more stable than non-magnetic ε iron up to about 50 GPa. Accounting for magnetism yields better agreement with the experimental equation of state, in contrast to the non-magnetic equation of state, which is in poor agreement with experiment below 50 GPa. We also studied non-collinear magnetism in γ- and ε-Fe. In ε-Fe the non-collinear effects are quite small energetically; in its stability field the collinear afmII structure is more stable than all non-collinear structures we explored. [Copyright &y& Elsevier]