Lubrication of dislocation glide in forsterite by Mg vacancies: insights from Peierls-Nabarro modeling

Abstract

Dislocation glide is an important contributor to the rheology of olivine under conditions of high stress and low to moderate temperature, such as occur in mantle wedges. Interactions between point defects and dislocation core may alter the Peierls stress,  p , and has been suggested that vacancy-related defects may selectively enhance glide on certain slip systems, changing the olivine deformation fabric.In this study, the Peierls-Nabarro model, parameterized by generalized stacking fault (GSF) energies calculated atomistically using empirical interatomic potentials, is used to determine the effect of bare concentration at the glide plane of 0.125 defects/site is sufficient to reduce cross-over to 0.7 GPa. This may account for the existence of the B-type olivine deformation fabric in the corners of mantle wedges.

Sliding Crack Model for Nonlinearity and Hysteresis in the Triaxial Stress‐Strain Curve of Rock, and Application to Antigorite Deformation

“…Nevertheless, we note that the cohesion y is about 0.7% of the antigorite's shear modulus at room temperature. Hence, the ratio is in the same order of magnitude as the ratio of the "lattice friction" or "Peierls stress" to shear modulus, assuming that such a ratio in antigorite is comparable to other existing measurements on silicates or carbonates (Nabarro, 1997) or computational estimates (Skelton & Walker, 2019).…”