Elasticity of ferropericlase at Earth's lower mantle conditions

The thermoelastic properties of ferropericlase Mg$_{1-x}$Fe$_{x}$O (x = 0.1875) across the iron high-to-low spin crossover at lower mantle conditions have been investigated by combining first principles calculations with a thermodynamics model of this system. At room temperature the transition is somewhat sharp and the effect on the bulk modulus is quite dramatic. Along a typical geotherm the transition should occur across most of the lower mantle with a noticeable bulk modulus reduction in the mid lower mantle. This transition should also alter noticeably the magnitude of velocity heterogeneities caused by lateral temperature changes.