The dynamics of the Earth's lower mantle, the largest continuous region of
the interior, plays a major role in controlling the thermal evolution of
the planet. The lower mantle extends from 660-2890 km depth (24-136 GPa) and
is inaccessible by direct observation. Observations of variations in the
velocity of seismic waves with position (heterogeneity) and with
propagation direction (anisotropy), promise a revolution in our
understanding of the dynamics of this important layer. However, this
expectation can only be fulfilled by comparable advances in our
understanding of the properties of the primary constituents of the lower
mantle. These allows the conversion of lateral variations
in velocity to lateral variations in temperature and composition, placing
constraints on Earth's thermal state and on the pattern of mantle
convection. First principles computations have led to major advances in
our understanding of elasticity and seismic wave propagation as well as
phase transitions at the high pressures and temperatures of the mantle.
However, it has just started scratching the surface of the formidable
challenges related to the fact that these phases are solid solutions
involving strongly correlated end members that may undergo spin
transitions under typical mantle pressures. This project consists in
tackling these challenges. (Wentzcovitch, de Gironcoli, Karki, and Allen)
