Atomistic Studies of the Structure and Properties of Grain Boundaries with Substitutional Impurities. Progress Report, July 1985-June 30, 1986

摘要

During this period, x-ray diffraction from sigma = 5 twist boundaries and the interatomic forces going beyond the commonly used pair-potentials were studied. In the former case the previously discovered multiplicity of grain boundary structures proved to be the key to understanding the observed diffraction patterns. In particular, while for any coincidence site lattice (CSL) periodic structure the agreement cannot be achieved, an excellent agreement is obtained for low energy, stable structures composed of pseudo-random mixture of units of two different types of CSL boundaries. In the latter case two schemes, one fully empirical using a many-body term based on the expansion of the density of states to the second moments, and the other using the full-scale tight binding method for solving Schroedinger equation, are used to develop description of interatomic forces suitable not only for structural studies of boundaries but also studies of cohesion, chemical effects, etc. (ERA citation 11:004680)