Plastic deformation of orthoenstatite and the ortho- to high-pressure clinoenstatite transition: a metadynamics simulation study
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Atomic-scale mechanisms of plastic deformation in orthoenstatite, MgSiO3 are studied by computer simulation methods. The combined use of metadynamics and molecular dynamics allows a direct observation of the structural changes during the creation of stacking faults in the (100) plane. A sequence of slip deformations in two different (100) planes at P = 15 GPa and T = 1,000 K reveals a probable transformation mechanism for the ortho- to high-pressure clinopyroxene transition. Each of the observed slips consists of at least four partial deformations crossing high-energy intermediate structures. In agreement with experimental studies, both (100) and (100) slip systems are activated in the deformation process. The observation of a dominant (100) single slip system in pyroxenes may be related to the fact that high-energy intermediate dislocations with (100) component are not stable on geological or experimental timescales.
KeywordsMolecular dynamics Metadynamics Phase transition Enstatite MgSiO3 Orthopyroxene Clinopyroxene
The authors thank W. Müller, R. Abart, S. Speziale and two reviewers for helpful comments and discussions. R.M. was partially supported by Grant No. VEGA 1/2011/05 and the Centre of Excellence of the Slovak Academy of Sciences (CENG).
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