Atomic core structure and mobility of [1 0 0](0 1 0) and [0 1 0](1 0 0) dislocations in MgSiO 3 perovskite

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

“…The atomic systems used throughout this study to explore the dislocation core properties and dislocation motion are designed according to the methodology described by Hirel et al (2014) for MgSiO 3 perovskite (bridgmanite) which was also shown to be appropriate for modeling both edge and screw [100] dislocations in post-perovskite (see discussion in Goryaeva et al 2015b). In this approach, a single dislocation is embedded into a simulation cell (Fig.…”

From glissile to sessile: Effect of temperature on 〈110〉 dislocations in perovskite materials

“…A series of experiments [3,4] and simulations [5,6] have provided a good understanding of the ductile behavior of STO at low temperature and demonstrated its direct link with the glide of 〈110〉 dislocations. However it is still unclear why this mechanism becomes inactive at high temperature, leading to brittle failure above 1050 K. It was initially proposed that 〈110〉 dislocations become sessile by dissociating into two 〈100〉 dislocations, or because of a change of preferential slip plane [2].…”

“…In high-pressure MgSiO 3 , [110] pc edge dislocations also spread in their ð110Þ pc glide plane, but with a much more compact core of width d = 13 Å. This core structure remains identical in a wide range of pressures, from 30 to 140 GPa [6].The high temperature core structures of the dislocations are obtained by performing molecular dynamics (MD) simulations for 10 to 20 ps at high temperature. A time step of 1 fs is used, and temperature is Scripta Materialia 120 (2016) 67-70…”

“…Atomic systems were constructed with Atomsk [12], and classical molecular statics and dynamics simulations were performed with LAMMPS [13]. Interatomic interactions in SrTiO 3 were modeled with the rigid-ion potential proposed by Thomas et al [14], and in MgSiO 3 with the one from Alfredsson et al [15].The glide-dissociated core structures of [110] pc edge dislocations were modeled by structural optimization in both materials [11,6]. The size of atomic systems is about 220 Å × 130 Å × c, verified to be large enough to ensure converged results.…”

Materials under pressure

“…The authors draw on examples from calculations on the pressure response to defect behavior in body-centered-cubic (bcc) metals, 35,36 and in ionic 37 and covalent systems to illustrate the wide variation possible. They extend this discussion to illustrate the contrasting behavior of two forms of MgSiO 3 , the perovskite 38 and the post-perovskite. 39 The transformation between the two is one of the more fundamental transformations in the Earth's deep mantle.…”