On the glide of [100] dislocation and the origin of ‘pencil glide’ in Mg<sub>2</sub>SiO<sub>4</sub>olivine

Mahendran, Srinivasan; Carrez, Philippe

doi:10.1080/14786435.2019.1638530

Cited by 6 publications

(4 citation statements)

References 48 publications

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“…However, did not observe discrete glide planes between (010) and ( 001) and noted that cross slip of [100] screw dislocations could give the appearance of pencil glide (Poirier 1975). Mahendran et al (2019) concluded from ab initio modeling that the cores of [100] screw dislocations can spread on {021} planes, giving the appearance of pencil glide.…”

Section: Comparison With Observations Ofmentioning

confidence: 99%

Dislocation structure of deformed olivine single crystals from conventional EBSD maps

Faul

2021

Phys Chem Minerals

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Dislocations, linear defects in a crystalline lattice characterized by their slip systems, can provide a record of grain internal deformation. Comprehensive examination of this record has been limited by intrinsic limitations of the observational methods. Transmission electron microscopy reveals individual dislocations, but images only a few square $$\upmu$$ μ m of sample. Oxidative decoration requires involved sample preparation and has uncertainties in detection of all dislocations and their types. The possibility of mapping dislocation density and slip systems by conventional (Hough-transform based) EBSD is investigated here with naturally and experimentally deformed San Carlos olivine single crystals. Geometry and dislocation structures of crystals deformed in orientations designed to activate particular slip systems were previously analyzed by TEM and oxidative decoration. A curvature tensor is calculated from changes in orientation of the crystal lattice, which is inverted to calculate density of geometrically necessary dislocations with the Matlab Toolbox MTEX. Densities of individual dislocation types along with misorientation axes are compared to orientation change measured on the deformed crystals. After filtering (denoising), noise floor and calculated dislocation densities are comparable to those reported from high resolution EBSD mapping. For samples deformed in [110]c and [011]c orientations EBSD mapping confirms [100](010) and [001](010), respectively, as the dominant slip systems. EBSD mapping thus enables relatively efficient observation of dislocation structures associated with intracrystalline deformation, both distributed, and localized at sub-boundaries, over substantially larger areas than has previously been possible. This will enable mapping of dislocation structures in both naturally and experimentally deformed polycrystals, with potentially new insights into deformation processes in Earth’s upper mantle.

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Section: Comparison With Observations Ofmentioning

confidence: 99%

Dislocation structure of deformed olivine single crystals from conventional EBSD maps

Faul

2021

Phys Chem Minerals

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“…This arrangement, which can only be described at the atomic scale, has a strong influence on the mobility of the dislocation and hence on mechanical properties. In a mineral like olivine, with complex crystal chemistry and structure, the core structure is rather complicated, with multiple possi- ble configurations (e.g., as a function of pressure) and even possible transient cores (see Mahendran et al, 2019).…”

Section: Nomenclature and Mechanisms Of Motionmentioning

confidence: 99%

Defects in olivine

Demouchy¹

2021

Eur. J. Mineral.

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Abstract. Olivine, a ferromagnesian orthosilicate, is the most abundant mineral in Earth's upper mantle and is stable down to the olivine–wadsleyite phase transition, which defines the 410 km depth mantle transition zone. Olivine also occurs in crustal environments in metamorphic and hydrothermal rocks and is expected to be the major mineral constituent of the Martian and Venusian mantles. The olivine atomic structure is also used in materials science to manufacture lithium batteries. Like any other crystalline solid, including minerals, olivine never occurs with a perfect crystalline structure: defects in various dimensions are ubiquitous, from point, line, and planar defects to three-dimensional (3-D) inclusions. In this contribution, I review the current state of the art of defects in olivine and several implications for key processes occurring in Earth's mantle. Intrinsic and extrinsic point defects are detailed, exemplifying the astonishing diversity of atomic impurities in mantle-derived olivine. Linear defects, one of the key defect types responsible for ductile deformation in crystalline solids, are examined in light of recent progress in 3-D transmission electron microscopy, which has revealed an important diversity of dislocation slip systems. I summarize the principal characteristics of interface defects in olivine: the free surface, grain and interface boundaries, and internal planar defects. As the least-studied defects to date, interface defects represent an important challenge for future studies and are the main application of numerical simulation methods in materials science. I provide an overview of melt, fluid, and mineral inclusions, which are widely studied in volcanology and igneous petrology. Special attention is given to new crystalline defects that act as deformation agents: disclinations (rotational defects) and the potential occurrence of disconnections in olivine, both of which are expected to occur along or near grain boundaries. Finally, I detail outstanding questions and research directions that will further our understanding of the crystalline specificities and paradoxes of olivine and olivine-rich rocks and ultimately their implications for the dynamics of Earth's upper mantle.

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“…More recently, the empirical potential formulation used by Walker and co-workers was implemented into the molecular dynamics package LAMMPS [46] opening the route to revisit the dislocation core structure and properties in olivine [47]. As an example, in a recent study of Mahendran et al [48], a detailed investigation of the structure of dislocations with a [100] Burgers vector highlighted the capabilities of [100] screw dislocations to cross-slip in various planes resulting in a pencil glide mechanism as invoked by Raleigh in olivine [26]. Up to now, in case of dislocations with a [001] Burgers vector, only one compact core structure of the screw dislocation has been reported [43,45,47].…”

Section: Introductionmentioning

confidence: 99%

The core structure of screw dislocations with [001] Burgers vector in Mg 2 SiO 4 olivine

Mahendran¹,

Carrez²,

Cordier³

2021

Comptes Rendus. Physique

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In this study, we report atomistic calculations of the core structure of screw dislocations with [001] Burgers vector in Mg 2 SiO 4 olivine. Computations based on the THB1 empirical potential set for olivine show that the stable core configurations of the screw dislocations correspond to a dissociation in {110} planes involving collinear partial dislocations. As a consequence, glide appears to be favorable in {110} planes at low temperature. This study also highlights the difference between dislocation glide mechanism in {110} versus (010) or (100) for which glide is expected to occur through a locking-unlocking mechanism. Résumé. Dans cette étude, nous présentons les résultats de calculs atomiques de la structure de coeur de la dislocation vis de vecteur de Burgers [001] dans l'olivine (Mg,Fe) 2 SiO 4. Nos simulations, reposant sur l'utilisation du potentiel semi-empirique THB1, montrent que la configuration stable de la dislocation vis correspond à une structure de coeur dissociée dans les plans {110}. A basse température, le glissement des dislocations de vecteur de Burgers [001] dans les plans {110} de l'olivine est donc favorisé.

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On the glide of [100] dislocation and the origin of ‘pencil glide’ in Mg₂SiO₄olivine

Cited by 6 publications

References 48 publications

Dislocation structure of deformed olivine single crystals from conventional EBSD maps

Dislocation structure of deformed olivine single crystals from conventional EBSD maps

Defects in olivine

The core structure of screw dislocations with [001] Burgers vector in Mg 2 SiO 4 olivine

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On the glide of [100] dislocation and the origin of ‘pencil glide’ in Mg2SiO4olivine

Cited by 6 publications

References 48 publications

Dislocation structure of deformed olivine single crystals from conventional EBSD maps

Dislocation structure of deformed olivine single crystals from conventional EBSD maps

Defects in olivine

The core structure of screw dislocations with [001] Burgers vector in Mg 2 SiO 4 olivine

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On the glide of [100] dislocation and the origin of ‘pencil glide’ in Mg₂SiO₄olivine