Correlation between the energy and structure of grain boundaries in b.c.c. metals. II. Symmetrical tilt boundaries

Abstract

The correlation between the structure and zero-temperature energy of symmetrical tilt grain boundaries (STGBs) in b.c.c. metals is investigated using a many-body potential of the Finnis-Sinclair type for Mo and Johnson's pair potential spline-fitted for α-Fe. As in free surfaces, the misorientation phase space associated with these simple planar defects consists of only two macroscopic degrees of freedom, namely those defining the grain-boundary (GB) plane normal. In a novel approach, the two-dimensional phase space is investigated in terms of a stereographic triangle and not in terms of the usual three parameters associated with the boundary misorientation. A comparison with similar calculations for free surfaces demonstrates the importance of the translational (microscopic) degrees of freedom in grain boundaries, while the comparison with STGBs in f.c.c. metals elucidates the important role played by the GB plane.