Plastic deformation of wadsleyite: IV Dislocation core modelling based on the Peierls–Nabarro–Galerkin model

Modeling dislocation glide and lattice friction in Mg2SiO4wadsleyite in conditions of the Earth’s transition zone

“…Wadsleyite is a sorosilicate with an orthorhombic crystal structure of space group Imma. Previous studies (Dupas et al 1994;Sharp et al 1994;Dupas-Bruzek et al 1998;Thurel 2001;Thurel et al 2003b;Metsue et al 2010) suggest that the two easiest slip systems are ½<111>{101} and [100](010). They involve dislocations dissociated into collinear partials.…”

“…However, in contrast to the latter hypothesis, Ritterbex et al (2015) show the inefficient contribution of dislocation glide to the overall plasticity of Mg 2 SiO 4 ringwoodite under transition zone conditions. Starting from Metsue et al (2010), who calculated the easiest slip systems and determined the associated dislocation core structures in Mg 2 SiO 4 wadsleyite at 15 GPa, the aim of the present work is to determine the glide mobility of these rate-controlling dislocations as a function of stress and temperature. Since the modeling approach of Ritterbex et al (2015) was based on the mobility of dissociated dislocations, the same methods will be applied to investigate the potential contribution of dislocation glide to the plasticity of wadsleyite under the conditions of the upper transition zone.…”

“…To move in high-pressure silicates such as wadsleyite, dislocations have to overcome their intrinsic lattice resistance. Plastic slip in this so-called thermally activated regime, is mainly governed by the sluggish glide of long ½<111>{101} and [100](010) screw segments (Metsue et al 2010). If a dislocation bows out in its glide plane under the conjugate action of stress and thermal activation, it activates non-screw segments that leave behind straight slow-moving screw lines, which in turn will account for most of the plastic strain produced.…”

Crystal defects in dense hydrous magnesium silicate phase A deformed at high pressure: characterization by transmission electron microscopy

“…Generalized stacking fault calculations have shown recently, however, that the absence of [010] dislocations is due in fact to the difficulty of shearing the olivine structure along this direction (Durinck et al, 2005). In wadsleyite, [010] dislocations exhibit very large Burgers vectors (11.44 Å), however, the core energy is relaxed by complex dissociation schemes (Thurel & Cordier, 2003, Metsue et al, 2010. Garnets, for which the Burgers vectors of ½<111> dislocations is ca.…”

Atomic-scale models of dislocation cores in minerals: progress and prospects

“…There has also been a detailed comparison between results from the two approaches, which provides a useful illustration of their relative strengths and weaknesses . More recently attention has turned to wadsleyite, which has also been studied using the PN and cluster approaches (Metsue et al 2010;Walker 2010). Ringwoodite was the subject of one of the early PN studies of mantle minerals, which provides a good example of this approach (Carrez et al, 2006).…”