Ab initio study of the composition dependence of the pressure-induced spin crossover in perovskite (Mg1−x,Fex)SiO3

摘要: Abstract We present ab initio calculations of the zero-temperature iron high- to low-spin crossover in (Mg 1 −  x Fe )SiO 3 perovskite at pressures relevant Earth's lower mantle. Equations state are fit for a range compositions and used predict spin transition pressure associated changes volume bulk modulus. dramatic decrease as concentration increases. This trend is contrary that seen ferropericlase, suggests energetics highly dependent on structural environment Fe. Both Local Density Approximation (LDA) Generalized Gradient (GGA) exchange-correlation methods used, both reproduce same compositional trends. However, GGA gives significantly higher than LDA. The made easier by decreasing spin-flip energy with but also driven change from high low spin. Volume trends show high-spin 2+ larger Mg even under pressure, smaller ambient conditions approximately size indicating less compressible . find large between slope concentration. Although these small absolute magnitude content, they still important when measured per could be calculating partitioning coefficients