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Title: Electronic structure study of screw dislocation core energetics in Aluminum and core energetics informed forces in a dislocation aggregate

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Journal Article: Publisher's Accepted Manuscript
Journal Name:
Journal of the Mechanics and Physics of Solids
Additional Journal Information:
Journal Volume: 104; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-10-07 09:07:39; Journal ID: ISSN 0022-5096
Country of Publication:
United Kingdom

Citation Formats

Das, Sambit, and Gavini, Vikram. Electronic structure study of screw dislocation core energetics in Aluminum and core energetics informed forces in a dislocation aggregate. United Kingdom: N. p., 2017. Web. doi:10.1016/j.jmps.2017.03.010.
Das, Sambit, & Gavini, Vikram. Electronic structure study of screw dislocation core energetics in Aluminum and core energetics informed forces in a dislocation aggregate. United Kingdom. doi:10.1016/j.jmps.2017.03.010.
Das, Sambit, and Gavini, Vikram. Sat . "Electronic structure study of screw dislocation core energetics in Aluminum and core energetics informed forces in a dislocation aggregate". United Kingdom. doi:10.1016/j.jmps.2017.03.010.
title = {Electronic structure study of screw dislocation core energetics in Aluminum and core energetics informed forces in a dislocation aggregate},
author = {Das, Sambit and Gavini, Vikram},
abstractNote = {},
doi = {10.1016/j.jmps.2017.03.010},
journal = {Journal of the Mechanics and Physics of Solids},
number = C,
volume = 104,
place = {United Kingdom},
year = {Sat Jul 01 00:00:00 EDT 2017},
month = {Sat Jul 01 00:00:00 EDT 2017}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.jmps.2017.03.010

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Cited by: 2works
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  • Cited by 8
  • The recombination process of dislocations is central to cross-slip, and transmission through Σ3 grain boundaries among other fundamental plastic deformation processes. Despite its importance, a detailed mechanistic understanding remains lacking. In this paper, we apply a continuous dislocation model, inspired by Peierls and Nabarro, complete with an ab-initio computed -surface and continuous units of infinitesimal dislocation slip, towards computing the stress-dependent recombination path of both an isotropic and anisotropic Cu screw dislocation. Under no applied stress, our model reproduces the stacking fault width between Shockley partial dislocations as predicted by discrete linear elasticity. Upon application of a compressive Escaig stress,more » the two partial dislocations coalesce to a separation of ~|b|. Upon increased loading the edge components of each partial dislocation recede, leaving behind a spread Peierls screw dislocation, indicating the recombined state. We demonstrate that the critical stress required to achieve the recombined state is independent of the shear modulus. Rather the critical recombination stress depends on an energy difference between an unstable fault energy (γτ) and the intrinsic stacking fault energy (γτ-γisf). We report recombination energies of ΔW = 0.168 eV/Å and ΔW = 0.084 eV/Å, respectively, for the Cu screw dislocation within isotropic and anisotropic media. Finally, we develop an analytic model which provides insight into our simulation results which compare favourably with other (similar) models.« less
  • In this work, we report a first-principles investigation of the energetics, structures, electronic properties, and core-level shifts of NO adsorption on the Pt(111) surface. Our calculations are based on density functional theory within the framework of the ultrasoft pseudopotential plane-wave and the all-electron projected augmented-wave methods. We found that at 0.25, 0.50, and 0.75 monolayer, NO adsorbs preferentially in the fcc, fcc+top, and fcc+top+hcp sites, respectively. The geometric parameters, adsorption energies, vibrational frequencies, and work-function changes are in good agreement with the experimental data. The interaction between NO and Pt(111) was found to follow a donation-back-donation process, in which themore » NO {sigma} states donate electrons to the substrate Pt d states, while the substrate Pt d states back donate to the NO {pi} states. Though there is an overall net charge transfer from the substrate to the NO adsorbate regardless of the adsorption sites and coverages, the spatial redistribution of the transferred electron is site dependent. The charge accumulation for NO in the top sites occurs closer to the surface than NO in the hollow sites, which results in the reduction of the Pt(111) surface work function for the top NO but an increase for the hollow NO. The core-level shifts of the topmost surface Pt atoms coordinated with top and hollow NO molecules at different coverages are in excellent agreement with experiments. In contrast, the N 1s core-level shifts between top and hollow NO ({approx}0.7 eV) deviated significantly from the zero shift found in experiments. Our analysis indicates that the difference may come from the thermal vibration and rotation of adsorbed NO on the Pt(111) surface.« less
  • The core structure and Peierls stress of the 1/2 〈111〉(110) screw dislocation in Ta have been investigated theoretically using the modified Peierls–Nabarro theory that takes into account the discreteness effect of crystal. The lattice constants, the elastic properties, and the generalized-stacking-fault energy(γ-surface) under the different pressures have been calculated from the electron density functional theory. The core structure of dislocation is determined by the modified Peierls equation, and the Peierls stress is evaluated from the dislocation energy that varies periodically as dislocation moves. The results show the core width and Peierls stress in Ta are weakly dependent of the pressuremore » up to 100 GPa when the length and stress are measured separately by the Burgers vector b and shear modulus μ. This indicates that core structure is approximately scaling invariant for the screw dislocation in Ta. The scaled plasticity of Ta changes little in high pressure environment.« less
  • Grazing-incidence synchrotron white beam x-ray topography images of closed-core threading screw dislocations in 4H silicon carbide appear as roughly elliptically shaped white features, with an asymmetric perimeter of dark contrast which is greatly enhanced on one side or other of the g vector. Ray-tracing simulations indicate that the relative position of the enhanced dark contrast feature reveals the sense of the closed-core screw dislocation. Dislocation senses so obtained were validated using back-reflection images recorded with small Bragg angle. Therefore, the sense of the closed-core threading screw dislocations can be unambiguously revealed using either grazing-incidence or 'small Bragg angle' back-reflection synchrotronmore » white beam x-ray topography.« less