Structural Vacancy Model of Grain Boundaries

A structural vacancy model of tilt grain boundaries in metals has been developed. For construction of the stable structure of the boundary, the initial pattern was chosen according to the CSL model. The introduction of additional atoms and vacancies into the boundary region and shifting of atoms by the interatomic forces stabilize its structure. The criterion of a stable structure is the grain-boundary energy. The comparison of two main approaches to the stabilization of the grain structure demonstrated that changing the number of atoms at the boundary is more energetically advantageous than the relative shift of grains. The stability of the structure obtained has been studied under the shear stress. In the model developed, atomic structures obtained with pair and many-body potentials have been compared. The comparative analysis has shown that the grain-boundary structure does not depend on the choice of potential; atomic positions differ by less than 0.1 Å, which is 2.5% of the lattice parameter. The atomic structure is in agreement with experimental images of grain boundaries.