Accession Number : ADA329711

Title :   Mixed Atomistic/Continuum Studies of Defects in Electronic & Materials

Descriptive Note : Final rept. 1 Jan 92-31 Dec 94

Corporate Author : BROWN UNIV PROVIDENCE RI DIV OF ENGINEERING

Personal Author(s) : Freund, L. B. ; Ortiz, M. ; Phillips, R.

PDF Url : ADA329711

Report Date : 07 MAR 1995

Pagination or Media Count : 7

Abstract : Deformation processes in crystalline materials of engineering significance are considered which are beyond the reach or atomistic simulations, due to the need to consider practically significant volumes of material, and beyond the reach of continuum mechanics, due to need to consider physical aspects of material defects. This work is based on a method of spatial discretization well suited to multiple scale analysis and the explicit consideration of the lattice geometry in the reference consideration of the crystal. Computational strategies have been developed which (1) include stable lattice defects (dislocations) in the solution (2) yield an unambiguous value for dislocation core energy, (3) agree with atomistic theory over those small regions where they can be compared, and (4) produce an approach to integration of crystalline defect physics into continuum analysis which is currently being pursued for several applications. In addition, a continuum study of dislocation nucleation at the surface of a highly stressed solid has been pursued which takes into account the core structure of the dislocation. While the activation energy for this process estimated on the basis of dislocations without core features is unrealistically large, it is found that the inclusion of structure brings the activation energy estimates into the range of physically realizable behavior.

Descriptors :   *CONTINUUM MECHANICS, *CRYSTAL DEFECTS, *DEFECT ANALYSIS, PLASTIC DEFORMATION, FINITE ELEMENT ANALYSIS, SHEAR MODULUS, NUCLEATION, DISLOCATIONS, POLYCRYSTALLINE, ACTIVATION ENERGY, CRYSTAL SUBSTRUCTURE.

Subject Categories : Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE