Meeting room "Glova", 4 floor, Integrated Research Building
Abstract
Plastic deformation of minerals in rocks plays an important role in the global convection of the Earth's mantle. However, the deformation mechanisms of minerals are not well-known.
In general, plastic deformation is due to the dislocation motion. Dislocations are linear defects of the crystal. The mobility of the dislocation is governed by the dislocation core structure at the atomic scale.
Here, we used the Peierls-Nabarro model that is a theoretical model to address the issue of dislocation core structure modeling. This model also provides the lattice friction of the crystal against the dislocation motion through the calculation of the Peierls stress. Developed more than 50 years ago, the model has been of great interest since the 70's with the introduction of the generalized stacking fault (GSF) concept that provides a general description of the dislocation core. The determination of the GSF consists in the calculations of energy barriers associated with the shearing of the crystal in a crystallographic plane in one or more directions.
In this study, we have determined the dislocation core structures of the post-perovskite phase present at the core-mantle boundary and of wadsleyite, diopside and forsterite, which are major minerals from the crust to 510 km deep.
We used the one-dimension formulation of the Peierls-Nabarro model in a first time that has been extended to three dimensions in order to model much more complex dislocation cores. The determination of the finest dislocation structures and the hardness of slip systems, calculated through the Peierls stress, gives a new understanding of the mechanisms of plasticity at the atomic scale which occur in the Earth's mantle.
For inquiry：Taku Tsuchiya TEL:（089）927-8198
E-mail takut@sci.ehime-u.ac.jp
