Explaining the dependence of M-site diffusion in forsterite on silica activity: a density functional theory approach.

ABSTRACT: Experimentally, silica activity (aSiO₂) has been shown to have an effect on Mg diffusion in forsterite, but no fully satisfactory mechanism has yet been proposed. We calculated the effects of aSiO₂ and aluminium content (the main contaminant in some recent experimental studies), and their co-effect, on Mg diffusion in forsterite, using thermodynamic minimisations of defect formation energies [calculated using density functional theory (DFT)] and a Monte-Carlo diffusion model. These two variables, in isolation, do not appreciably change the defect concentrations of forsterite and thus do not affect the diffusivity of Mg. However, when elevated together, they cause large increases in the Mg vacancy content and thus can increase the Mg diffusivity by one to six orders of

SUBMITTER: Muir JMR 

PROVIDER: S-EPMC7686175 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature