Atomistically-informed polycrystalline simulations: how do MgO polycrystals deform under pressure?
Abstract
In MgO, which is a major constituent of the Earth's lower mantle, the relative activity of the ½⟨110⟩{110} and 1/2⟨110⟩{100} slip modes depends on the level of hydrostatic pressure. The influence of pressure on both the dislocation core structures and the collective behavior of dislocations may be computed based on atomistic modeling and dislocation dynamics simulations. In the present study, results from such lower-scale simulations are used to determine the parameters of a crystal plasticity model that is suitable in order to probe the large-scale mechanical response of MgO polycrystals at pressures up to 100 GPa1. The model is assessed based on diamond anvil cell (DAC) deformation tests performed at different pressure levels. The influence of the different slip modes is discussed as well as the role played by the dislocation density. It turns out that the responses of single crystals and polycrystals are fundamentally different. Moreover, due to the large anisotropy of individual crystals, the outcome of polycrystalline simulations is found to depend strongly on the modeling assumption made about grain interactions. Crystal plasticity based finite element modeling provides the best predictions of the texture development when comparing to recent high-pressure experiments. DAC and D-DIA results are reinterpreted in the light of this multi-scale deformation framework as well as on recent in situ TEM tests. 1. Amodeo, J., Dancette, S. & Delannay, L. Atomistically-informed crystal plasticity in MgO polycrystals under pressure. Int. J. Plasticity 82, 177-191 (2016).
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMMR14A..03A
- Keywords:
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- 3909 Elasticity and anelasticity;
- MINERAL PHYSICSDE: 3924 High-pressure behavior;
- MINERAL PHYSICSDE: 5120 Plasticity;
- diffusion;
- and creep;
- PHYSICAL PROPERTIES OF ROCKSDE: 5430 Interiors;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS