Numerical modelling of dislocations and deformation mechanisms in CaIrO3 and MgGeO3 post-perovskites—Comparison with MgSiO3 post-perovskite

Abstract

Please cite this article as: Metsue, A., Carrez, P., Mainprice, D., Cordier, P., Numerical modelling of dislocations and deformation mechanisms in CaIrO 3 and MgGeO 3 postperovskites -Comparison with MgSiO 3 post-perovskite, Physics of the Earth and Planetary Interiors (2007), doi:10.1016/j.pepi.2008 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A c c e p t e d M a n u s c r i p t 2 Abstract:In this study, we propose a theoretical approach to test the validity of the isomechanical analogues for post-perovskite structures. Intrinsic plastic properties are evaluated for three materials exhibiting a post-perovskite phase: MgSiO 3 , MgGeO 3 and CaIrO 3 .Dislocation properties of each structure are determined using the Peierls-Nabarro model based on first principles calculations of generalised stacking fault and the plastic properties are extended to crystal preferred orientations using a visco-plastic selfconsistent method. This study provides intrinsic parameters of plastic deformation such as dislocation structures and Peierls stresses that can be directly compared between the three materials. It appears that it is very difficult to draw any simple conclusions on polycrystalline deformation simply by comparing single crystal properties. In particular, contrasting single crystal properties of MgSiO 3 and CaIrO 3 lead to similar crystal preferred orientation of the polycrystal aggregates.

Modeling defects and plasticity in MgSiO3 post-perovskite: Part 3—Screw and edge [001] dislocations

“…In agreement with predictions from previous GSF studies (Carrez et al 2007a;Metsue et al 2009;Goryaeva et al 2015a), we observe spontaneous dissociation of perfect [001] Volterra dislocations into two partials separated by a stacking fault in (010). The atomic structure of the relaxed screw dislocation core is illustrated in Fig.…”

“…Also, one should mind that in terms of bonding and octahedral distortions, characteristics of CaIrO 3 are not the same as in MgSiO 3 and its closest MgGeO 3 analog (Tsuchiya and Tsuchiya 2007;Hustoft et al 2008;. First-principles studies also indicate that anisotropic character of elasticity (Tsuchiya and Tsuchiya 2007) and plasticity (Metsue et al 2009) in CaIrO 3 are different from those in silicate post-perovskite. All these ambiguities, associated with the analog approach in plasticity, call for direct investigation of MgSiO 3 at relevant P-T conditions.…”

“…Previous studies of generalized stacking-fault (GSF) energies, also called γ-surfaces (Carrez et al 2007a;Metsue et al 2009;Goryaeva et al 2015a), have shown the presence of a stable stacking fault at half way when the crystal structure is sheared along [001] in the (010) plane. Thus, it is not surprising that early studies based on the Peierls-Nabarro (PN) model have suggested possible dissociation in (010) of [001] dislocations into two partials dislocations (Carrez et al 2007a;Metsue et al 2009).…”

“…Thus, it is not surprising that early studies based on the Peierls-Nabarro (PN) model have suggested possible dissociation in (010) of [001] dislocations into two partials dislocations (Carrez et al 2007a;Metsue et al 2009). In addition to that, the recent γ-surface calculations (Goryaeva et al 2015a) indicate that [001] dissociations can possibly exhibit a mixed character with the presence of <100> component, which could not be earlier described with the PN model (Carrez et al 2007a, b).…”

Synthetic seismic anisotropy models within a slab impinging on the core–mantle boundary

“…Devincre et al 2001;Walker et al 2010). These have also been applied to periclase ), perovskite (Cordier et al 2004;Mainprice et al 2008), and post-perovskite (Oganov et al 2005;Carrez et al 2007;Metsue et al 2009). …”