Anisotropy and anelasticity of HCP metals: a key to the dynamics of Earth’s inner core

The solid iron inner core is the most remote and inaccessible part of our planet but its structure and composition may provide a key record needed to untangle the geological history of the surface environment. Information encoded in the inner core during its solidification could reveal the timing and nature of the onset of Earth’s protective magnetic field generated by convection in the liquid outer core or even of changes in the way the mantle convects and drives surface dynamics. Key to developing our understanding of the inner core is our ability to use seismic observations to constrain its structure on all scales. Seismic wave velocities are mostly sensitive to the atomic scale crystal structure, temperature and composition. On a larger scale the microstructure of the inner core, reflecting its deformation and crystallization history, can be probed by seismic studies of elastic anisotropy (variation of wave velocity with direction) and anelasticity (responsible for the time lag between the deformation associated with the passage of seismic energy and recovery to the pre-strained state leading to seismic signals that can be observed in normal modes and body waves). Seismic observations in principle allow us to infer the inner core’s history of growth and deformation, but require information on the material properties of hexagonal close packed iron – the high-pressure phase of iron expected to form the inner core. The overall aim of this project is to make use of atomic scale simulations to provide this information. In particular, you will seek to understand the origin of anisotropy and analesticity in the inner core and use this understanding to decode the information hidden in the center of the Earth.

http://www.nercdtp.leeds.ac.uk/projects/index.php?id=507