Application of the Peierls-Nabarro model to dislocations in forsterite
Application of the Peierls-Nabarro model to dislocations in forsterite (in EMPG XI; Experimental mineralogy, petrology and geochemistry symposium, Jonathan D. Bundy (editor), Simon C. Kohn (editor) and Michael J. Walter (editor))
European Journal of Mineralogy (October 2007) 19 (5): 631-639
- crystal dislocations
- deformation
- forsterite
- hydrostatic pressure
- lattice
- mechanical properties
- microstructure
- nesosilicates
- numerical models
- olivine group
- orthosilicates
- plastic deformation
- pressure
- silicates
- strain
- stress
- three-dimensional models
- lattice friction
- dislocation cores
- Peierls-Nabarro model
- Schmid law
We present a numerical model of dislocation cores in Mg (sub 2) SiO (sub 4) forsterite based on the Peierls-Nabarro model and using generalised stacking faults as an input. The generalised stacking faults have been calculated from ab initio density-functional theory using VASP. Core profiles, atomic models and Peierls stresses are proposed for dislocations from the following slip systems: [100](010), [100](001), [100]{021}, [001](010), [001](100) and [001]{110}. Calculations have been performed at 0 and 10 GPa, to investigate the influence of pressure. We show that [100] dislocations have narrow cores when [001] dislocations tend to spread into (100) and {110} planes. A strong softening effect is found with pressure on the [001](010) slip system. Our study emphasizes the influence of lattice friction on plastic deformation of forsterite with, beyond Peierls stresses, possible effects related to non-planar core structures.
