Climb creep provides an efficient deformation mechanism for bridgmanite under lower mantle conditions.

Abstract Transport of heat from the interior Earth drives convection in mantle, which involves deformation solid rocks over billions years. The lower mantle is mostly composed iron-bearing bridgmanite MgSiO 3 and approximately 25% volume periclase MgO (also with some iron). It commonly accepted that ferropericlase weaker than 1 . Considerable progress has been made recent years to study assemblages representative under relevant pressure temperature conditions 2,3 However, natural strain...

The transport of heat from the interior Earth drives convection in mantle, which involves deformation solid rocks over billions years. Significant advancements have been made recent years to study lower mantle assemblages under relevant pressure and temperature conditions, confirmed usual view that ferropericlase is weaker than bridgmanite. However, natural strain rates are 8 10 orders magnitude those observed laboratory, remain inaccessible us. Once physical mechanisms their constituent...

In the present work, we use a numerical modelling approach based on 2.5-dimensional dislocation dynamics simulations to investigate transition between power and exponential laws in olivine for temperatures ranging 800 K 1700 stresses 100 500 MPa. We model deformation of an crystal by interplay glide climb dislocations. Plastic strain is produced glide, amount gliding dislocations being controlled acting as recovery mechanism. Within this framework, without need introducing any other...

In this study, we determined the core structure and Peierls stress of dislocations in Ti2AlN MAX phase. We use a generalized Peierls–Nabarro model, called Peierls–Nabarro–Galerkin (PNG), coupled with first principles calculations stacking fault (GSF). The GSF show that dislocation glide basal plane will occur preferentially between M (here Ti) A Al) planes. Additionally, results PNG demonstrate whatever character, are dissociated plane, dissociation distance below experimental resolution...

In this study, we model the core structure of screw dislocations with [1 0 0] and [0 1 Burgers vector in MgSiO3 perovskite, pressure range Earth's lower mantle (25–130 GPa). We use a generalized Peierls–Nabarro model, called Peierls–Nabarro–Galerkin, based on stacking-fault energy calculations. These calculations are performed using pairwise potential parametrization compared to ab initio results. The results Peierls–Nabarro–Galerkin demonstrate that dislocation are, respectively,...

Deformation resulting from thermally activated plastic slip is modeled in Mg2SiO4 ringwoodite at 20 GPa for a wide range of temperatures. The model relies on the structures rate controlling 1/2〈110〉 screw dislocations which have been using Peierls–Nabarro–Galerkin method. These calculations are parametrized by density functional theory γ-surfaces {001},{110} and {111} planes. At finite temperatures, dislocation mobility controlled kink-pair nucleation 1/4〈110〉 partial as they occur...

Imaging dislocation microstructures in 3D and monitoring their interactions over time is a major challenge. In this study, we show that enhancing the contrast of lines prior to reconstruction, allows optimize an acquisition phase with fewer images thus follow evolution microstructure time. We illustrate new possibility by studying first stages formation helical dislocations MgO under electron irradiation. highlight role segment mobility on initiation climb reveal existence preferential mixed planes.

In this study, we model the plasticity of MgO (periclase) using a 2.5-dimensional (2.5D) dislocation dynamics (DD) simulation approach. This allows us to incorporate climb in DD simulations creep behavior at high-temperature. Since 2D formulation cannot capture some important features activity (e.g. those involving line tension), local rules are introduced take these into account (this is 2.5D approach). To ensure validity such approach, applied over wide temperature range with view lower...

The ultimate mechanical properties, as characterized here by the ideal strengths of Mg2SiO4 forsterite, have been calculated using first-principles calculations and generalized gradient approximation under tensile shear loading. (ITS) (ISS) are computed applying homogeneous strain increments along high-symmetry directions ([100], [010], [001]) low index plane ((100), (010), (001)) orthorhombic lattice. We show that properties forsterite highly anisotropic, with ITS ranging from 12.1 GPa...

Evaporation and condensation rates are investigated for small clusters nanoparticles in the presence of a gas by using classical molecular dynamics. The effects initial cluster temperature size, as well density analyzed. surrounding characteristics found to strongly affect evolution. obtained simulation results analyzed based on collision rate Rice, Ramsperger, Kassel theory.

In this work, we investigate twist grain boundary (GB) energies and structures in Mg2SiO4 forsterite using atomistic simulations. We first present a new bond orientational order parameter allowing to highlight disordered regions low-symmetry crystal for which classical visualization tools are ineffective. Then examine three GB planes, (010), (120) (001), corresponding the most favorable free surfaces of crystal. show that follow same energy ordering as surfaces. addition, except some...

Abstract The dislocation emission surface in (k I, k II, III) space is calculated by means of atomistic simulations for the {111}⟨110⟩ crack Al. For each relevant combination loading mode, precise nature dislocations and process are determined. When appropriate, analytic formulas proposed Rice used calculating unstable stacking energy including effect mixed mode loading. Quantitative agreement with full calculation found case where glide plane. This clearly identifies when how ab initio data...

The ultimate mechanical properties of MgSiO3 orthoenstatite (OEN), as characterized here by the ideal strengths, have been calculated under tensile and shear loadings using first-principles calculations. Both strength (ITS) (ISS) are computed applying homogeneous strain increments along high-symmetry directions ([100], [010], [001]) low index planes ((100), (010), (001)) orthorhombic lattice. We show that OEN highly anisotropic during loading, with ITS ranging from 4.5 GPa [001] to 8.7...

The plasticity of the dense hydrous magnesium silicate (DHMS) phase A, a key mineral within cold subduction zones, was investigated by two complementary approaches: high-pressure deformation experiments and computational methods. were carried out at 11 GPa, 400 580 °C, with in situ measurements stress, strain lattice preferred orientations (LPO). Based on viscoplastic self-consistent modeling (VPSC) observed LPO, mechanisms °C are consistent glide (0 0 1) basal (011¯0) prismatic planes. At...

Numerical modeling is performed to study cluster formation by laser ablation. The developed model allows us compare the relative contribution of two channels production ablation: (i) direct ejection upon laser-material interaction, and (ii) collisional sticking, evaporation coalescence during ablation plume expansion. Both these mechanisms are found affect final size distribution. Plume composition correlated with dynamics. results calculations demonstrate that precursors formed material...

The main objective of this study is to explain the experimental observations. To simulate material ablation, plume formation and its evolution, we developed a combined molecular dynamics (MD) direct simulation Monte Carlo (DSMC) computational laser ablation evolution. first process described by MD method. expansion ejected modelled DSMC better understand evolution nanoparticles present in plume, used separate simulations analyse cluster presence background gas with different properties...