A technique is described for applying flexible boundaries to an atomic region in computer simulation of dislocations or other line defects. The method results in continuity of equilibrium, under the chosen interatomic potential, across the interface between the atomic region and the outer region described in terms of anisotropic elastic continuum solutions. The technique has high numerical efficiency. It is shown that when the crystal is initially dislocated according to the Volterra solution for displacements, the finite strains give rise to geometrical nonlinear effects, usually disregarded in linear elasticity, which contribute to a volume change of the crystal. Allowance for this effect, and for elastic nonlinearity in the crystal beyond the boundary region, allows the overall dilatation of a finite body due to the dislocation to be rigorously computed. For illustration of the geometric nonlinear effect, and for comparison with earlier modeling methods, examples of computations are given for the [1001 edge dislocation in a iron.
Atomistic study of temperature dependence of interaction between screw dislocation and nanosized bcc Cu precipitate in bcc FeAtomistic calculation of the core structure and Peierls energy of an (a/2) [110]
edge dislocation in MgOIt is shown that the strain field of a straight dislocation in an anisotropic elastic continuum includes an infinite series of terms of order 2 and higher in inverse distance from the dislocation line. These terms are determined by the nature of the core. A method is developed of finding these terms for a given dislocation while determining the core structure atomistically, using a digital computer. The equilibrium configuration of the core and the higher-order-term values are found rapidly by a method involving atomic force constants, which requires few calculations of interatomic forces. The model is applied to determine the core structure and near-strain field of a (100) edge dislocation in 01 iron using potentials developed by Johnson and by Chang and Graham. Core structure in agreement with that found by Gehlen et al. is obtained. The results are independent of model size over a wide range, and there is agreement between strain-energy distribution calculated atomistic ally and from elastic constants, for all three potentials used. The method may be useful in calculation of Peierls stress and of dislocation-point-defect interaction.
This report describes the observations and preliminary assessments of the members of the Reconnaissance Team of the New Zealand National Society for Earthquake Engineering which visited Kobe, Japan and the surrounding areas following the Hyogo-ken Nanbu earthquake of 17 January 1995. The report covers aspects of the effects of the earthquake on the ground, lifelines, buildings, bridges and other structures, and the community. Lessons for New Zealand are discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.