High-resolution transmission electron microscopy was used to study a  = 7 (12•0)/[00•1] 21.8 grain boundary in the -phase. Relaxed structural models and image simulations were used to investigate the boundary. The unrelaxed grain boundary was unstable, and could not properly reflect the grain boundary structure. A better model could be obtained by means of molecular statics simulations. The model structure which gave the best fit to experimental images was one in which the dislocation cores were separated by nearly perfect regions at the boundary. This also had the lowest energy (703mJ/m2). In this grain boundary, the dislocation cores were well-separated by the perfect regions. The structural unit of the dislocation core was unique in this low-angle boundary.

Y.Wang, J.Li, H.Ye: Philosophical Magazine A, 1996, 73[1], 213-22