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Diffusion in MgO at high pressure: Implications for lower mantle rheology
Author(s) -
Ita Joel,
Cohen Ronald E.
Publication year - 1998
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/98gl50564
Subject(s) - mantle (geology) , diffusion , impurity , rheology , grain boundary diffusion coefficient , thermodynamics , materials science , lattice diffusion coefficient , viscosity , geology , grain boundary , geophysics , effective diffusion coefficient , microstructure , chemistry , physics , medicine , organic chemistry , radiology , magnetic resonance imaging , metallurgy
Theoretical calculations of diffusion in periclase were performed to model the rheological properties of the lower mantle. Gibbs free energy values derived from molecular dynamics simulations using a non‐empirical interatomic potential to accurately predict diffusion in MgO at zero pressure. Diffusion coefficients were computed for pressures and temperatures up to 140 GPa and 5000 K. We find that Mg vacancies required for diffusive transport are likely extrinsic (due to impurities), and the resulting O vacancies would then be too few to support bulk O transport. Estimates of viscosity from these results are consistent with those inferred for the lower mantle from geophysical observations if grain boundary diffusion is responsible for O transport.