Showing papers by "Steven J. Plimpton published in 1998"
TL;DR: In this paper, an atomistic imaging of dislocation nucleation during displacement controlled indentation on a passivated surface is presented, where defects are located and imaged by local deviations from centrosymmetry.
Abstract: We model indentation of a metal surface by combining an atomistic metal with a hard-sphere indenter. This work provides atomistic imaging of dislocation nucleation during displacement controlled indentation on a passivated surface. Dislocations and defects are located and imaged by local deviations from centrosymmetry. For a Au(111) surface, nucleation of partial dislocation loops occurs below the surface inside the indenter contact area. We compare and contrast these observations with empirical criteria for dislocation nucleation and corresponding continuum elasticity solutions.
1,862 citations
TL;DR: In this paper, extensive molecular dynamics simulations are performed on a glass-forming Lennard-Jones mixture to determine the nature of the cooperative motions occurring in this model fragile liquid, and they observe stringlike cooperative molecular motion (''strings'') at temperatures well above the glass transition.
Abstract: Extensive molecular dynamics simulations are performed on a glass-forming Lennard-Jones mixture to determine the nature of the cooperative motions occurring in this model fragile liquid. We observe stringlike cooperative molecular motion (``strings'') at temperatures well above the glass transition. The mean length of the strings increases upon cooling, and the string length distribution is found to be nearly exponential.
807 citations
07 Nov 1998
TL;DR: This paper describes a grid transfer algorithm suitable for massively parallel codes which use multiple grids that uses a rendezvous technique wherein a third decomposition is used to search for elements in one grid that contain nodal points of the other.
Abstract: A number of computational procedures employ multiple grids on which solutions are computed. For example, in multi-physics simulations a primary grid may be used to compute mechanical deformation of an object while a secondary grid is used for thermal conduction calculations. When modeling coupled thermo-mechanical effects, solution data must be interpolated back and forth between the grids each timestep. On a parallel machine, this grid transfer operation can be challenging if the two grids are decomposed to processors differently for reasons of computational efficiency. If the grids move or adapt separately, the complexity of the operation is compounded. In this paper we describe a grid transfer algorithm suitable for massively parallel codes which use multiple grids. It uses a rendezvous technique wherein a third decomposition is used to search for elements in one grid that contain nodal points of the other. This has the advantage of enabling the grid transfer to be load-balanced separately from the remainder of the computations. The algorithm has been implemented as an object-oriented tool for the multi-physics code SIERRA, currently under development at Sandia. Performance and scalability results for the grid transfer operation running on the Intel/Sandia TFLOPS supercomputer are presented.
22 citations