简介: Abstract

The discovery of the high-to-low spin crossover transition in iron in ferropericlase, a major mineral of Earth′s lower mantle, has raised a number of questions concerning the effects of this transition on mantle properties. Of primary importance is the effect of this transition on the elastic properties of this mineral and mantle aggregates. These are used to interpret seismic data and extract conclusions regarding the temperature, composition, and mineralogy of the lower mantle. We have investigated by first principles the thermoelastic properties of ferropericlase, Mg1-xFexO (x = 0.1875), throughout the spin transition at lower mantle conditions. We have computed quasiharmonic free energies using a vibrational virtual crystal model for the pure spin cases and predict spin populations and thermodynamics properties. We show that this transition has important consequences for the elastic properties such as an anomalous bulk modulus reduction that broadens with increasing temperature.

[1]、Tsuchiya, T., Wentzcovitch, R. M., da Silva, C. R. S., de Gironcoli, S. , Spin transition in Magnesiowüstite in Earth’s lower mantle, Phys, Rev, Lett., 96, 198501 (2006).
[2]、Wentzcovitch, R. M., Justo, J.F., Wu, Z., da Silva, C. R. S., Yuen, D., and  Kohlstedt, D., Anomalous compressibility of ferropericlase throughout the iron spin crossover, Proc. Natl. Acad. Sc. USA,  in press (2009).