Anomalous compressibility of ferropericlase throughout the iron spin cross-over.
The thermoelastic properties of ferropericlase Mg(1-x)Fe(x)O (x = 0.1875) throughout the iron high-to-low spin cross-over have been investigated by first principles at Earth's lower mantle conditions. This cross-over has important consequences for elasticity such as an anomalous bulk modulus (K(S)) reduction. At room temperature the anomaly is somewhat sharp in pressure but broadens with increasing temperature. Along a typical geotherm it occurs across most of the lower mantle with a more significant K(S) reduction at approximately 1,400-1,600 km depth. This anomaly might also cause a reduction in the effective activation energy for diffusion creep and lead to a viscosity minimum in the mid-lower mantle, in apparent agreement with results from inversion of data related with mantle convection and postglacial rebound.
Wentzcovitch
R M
RM
Department of Chemical Engineering and Materials Science, Minnesota Supercomputing Institute, Minneapolis, MN 55455, USA. wentzcov@cems.umn.edu
Justo
J F
JF
Wu
Z
Z
da Silva
C R S
CR
Yuen
D A
DA
Kohlstedt
D
D