Simulation of screw dislocations in wadsleyite

Walker, Andrew

doi:10.1007/s00269-009-0334-y

Cited by 9 publications

(15 citation statements)

References 61 publications

(60 reference statements)

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“…Furthermore, a tinier dislocated volume entails smaller strains to the reminder of the crystal too. A somewhat analogous pattern of inward movements of screw dislocations have been reported earlier …”

Section: Resultssupporting

confidence: 79%

“…Recent cluster embedded models centered on 1D periodic boundary conditions (PBC) can thoroughly examine a single dislocation with atomistic scale reliability. In this work, we use a cluster model that has been very successful in examining dislocations in numerous compounds such as MgO, complex crystals (β‐Mg 2 SiO 4 ), paracetamol (OH‐C 6 H 4 NHCOCH 3 ), and others …”

Section: Introductionmentioning

confidence: 99%

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Structure, Energetics, and Impact of Screw Dislocations in Tricalcium Silicates

2016

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Understanding and quantifying the atomic structure, energetics, and the effect of defects on mechanics and reactivity of low symmetry oxides is an engineering challenge. This study focuses on atomistic analysis of screw dislocation in three thermodynamically reversible polymorphs of tricalcium silicate (Ca 3 SiO 3 ), which is the key ingredient of cement. We employ molecular simulations to decode the interplay between the dislocation formation core energies, nonplanar core structures, displacement fields, disregistry functions, and Peierls stresses of tricalcium silicate polymorphs. By analyzing the core geometry at multiple scales, we found that the screw dislocations minimally impact the atomic bonds and angles at the vicinity of the Ca 3 SiO 3 core dislocations, largely due to the sizeable channels and rigid body type relocation of atoms, which moderate most of the disturbances enforced by dislocations. Furthermore, we found that while the rhombohedral C3S (R-C3S) exhibits a relatively large core energy and core radius, the two monoclinic C3S structures (M3-C3S and MM-C3S) exhibited lower and almost identical core energies and core radii, likely due to the fact that they are two crystal realizations of the same polymorph. Finally, we discuss the implications of this work on brittleness and reactivity of cement crystals, and potential opportunities to better understand and modulate the grinding energy, reactivity, and mechanical properties of cement clinkers.

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Section: Resultssupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Structure, Energetics, and Impact of Screw Dislocations in Tricalcium Silicates

2016

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“…Previous simulations based on 2D geometries, have investigated grain-boundary process 15 . The use of 1D methods for investigating the structure of dislocations in ionic solids is still in its infancy but is already proving to be a valuable tool 8,16 . For example, simulations by Walker et al 17 on siliceous zeolite A (LTA) showed how the introduction of a screw dislocation, observed by AFM 18 , would lead to blocking of channels normal to the dislocation line.…”

Section: Atomistic Simulation Methods Have Been Enormously Successfulmentioning

confidence: 99%

Defects and dislocations in MgO: atomic scale models of impurity segregation and fast pipe diffusion

et al. 2010

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Graphical contents entry Atomic scale simulations show the path taken by magnesium vacancies undergoing rapid pipe diffusion along the core of a edge dislocation in MgO. S ummary Dislocations are known to influence the formation and migration of point defects in crystalline materials. We use a recently developed method for the simulation of the cores of dislocations in ionic materials to study the energy associated with the formation of point defects close to the core of a edge dislocation in MgO. These are compared then with the energies for the same point defects in otherwise perfect MgO. It is find that all defect species are bound to the dislocation core, with binding energies of between 1.5 and 2.0 eV. Vacancies are found to be most stable when they remove undercoordinated ions at the tip of the extra half plane, while the impurities are most stable within the dilatational stress field below the glide plane. By mapping the distribution of energies for point defects around the dislocation line we reveal the coupling between the effective point defect size and the stress field associated with the dislocation. We also examine the energy barrier to diffusion of vacancies along the dislocation line and find that vacancy migration along the dislocation line will be substantially enhanced compared to migration through the dislocation free crystal structure. Activation energies are 0.85-0.92 of the barrier in the perfect crystal, demonstrating the importance of pipe diffusion along extended defects for low temperature mobility in ionic materials.

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“…The exact recipe for achieving this depends on the charges assigned to the cations and the polyhederal connectivity in the mineral. Increasingly involved examples are given in the literature for a puresilica zeolite (Walker et al, 2004), forsterite (Walker et al, 2005b) and wadsleyite (Walker, 2010).…”

Section: Methodsmentioning

confidence: 99%

“…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).…”

Section: Forsterite Wadsleyite and Ringwooditementioning

confidence: 99%