Symmetrical and asymmetrical S = 3 <112> tilt grain boundaries were investigated by using atomistic computer simulations. Equilibrium energies and structures were calculated by means of static and dynamic energy minimization. A semi-empirical N-body potential served as a model for the interatomic forces. The atomic structure of a grain boundary which was inclined at about 84° to the {111} twin boundary was investigated by using high-resolution transmission electron microscopy. When plotted against the inclination angle of the boundary plane, the calculated grain boundary energies increased monotonically up to 73°. At higher inclination angles, the data indicated the existence of an energy minimum at about 80°. The computer simulations predicted that boundaries which were equilibrated at temperatures near to 0K were planar for inclination angles of less than 73°, but consisted of a 3-dimensional layer of predominantly body-centred cubic Cu at inclination angles that were greater than 73°. In all 3-dimensional boundaries the body-centered cubic layer was about 1nm wide in the direction perpendicular to the boundary plane. By analyzing the micro-faceting of these boundaries, and its influence upon the misfit strain of the body-centered cubic layer, the observation of a local energy minimum close to 80° was explained. In the case of a boundary which was inclined at about 84°, calculated atomistic structures and the high-resolution transmission electron microscopic images exhibited striking similarities. This suggested that the body-centered cubic crystal structure was the equilibrium structure within this grain boundary at low temperatures.

Theoretical and Experimental Investigations of Structures and Energies of S = 3, [112] Tilt Grain Boundaries in Copper C.Schmidt, M.W.Finnis, F.Ernst, V.Vitek: Philosophical Magazine A, 1998, 77[5], 1161-84