EAR-PF: Diffusion anisotropy in Earth's inner core

Pigott Jeffrey S, Columbus OH

Investigators

Abstract

Dr. Jeffrey Pigott has been awarded an NSF Earth Sciences Postdoctoral Fellowship to conduct research at Case Western Reserve University (CWRU) and carry out activities to broaden participation in the Earth sciences. Earth's inner core has recently been revealed to be structurally complex, with significant seismic anisotropy, seismic waves traveling faster in the polar direction than in the equatorial plane. This seismic anisotropy varies in magnitude hemispherically and as a function of depth. This project aims to determine how this seismic anisotropy relates to crystal structure and solid-state deformation. To increase diversity in the geosciences, Dr. Pigott will mentor an undergraduate researcher and leverage existing partnerships with Cleveland area high schools. The seismic anisotropy in Earth's inner core likely results from crystallographic preferred orientation of the hexagonal close-packed (hcp) iron-nickel alloy that is thought to be stable under inner core conditions, but how this texturing developed remains a subject of debate. Constraining the diffusion anisotropy and solid-state viscosity of the inner core is critical to understanding the link between deformation and seismic anisotropy. Dr. Pigott will quantify the self-diffusion anisotropy in Earth's inner core through atomistic simulations and first principles calculations of the axial self-diffusion coefficients in hcp-Fe at inner core conditions coupled with diffusion experiments using the analog metal hcp-Zn. Internally-consistent first principles calculations of the elasticity of hcp-Fe will elucidate the relationship between diffusion, deformation, and elasticity and allow for robust modeling of the state and evolution of Earth's inner core.