High resolution transmission electron microscopy (HRTEM) has been applied to verify the validity of the O-lattice theory for geometrical approach to the grain boundary structure, then periodic structures predicted from the O-lattice theory have been compared with the HRTEM images. In addition, the correlation between the grain boundary energy and the grain boundary structure has been discussed. Main results obtained are as follows. (1) The predicted periodic structure of an arbitrary 〈110〉 symmetric tilt grain boundary is consistent well with the observed one irrespective of the nature of the atomic bonding. (2) There is a good correlation between the misorientation-dependence on grain boundary dislocation density and that on grain boundary energy, suggesting that main part of the grain boundary energy comes from elastic and core energies of grain boundary dislocations. (3) The energy per grain boundary dislocation is less dependent of the magnitude of the Burgers vector but depends on the parameter defined as the grain boundary dislocation density normalized by their Burgers vector, b/D, within the range of 0.1 ≲ b/D ≲ 1.
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