The possibility of a melting-type grain boundary disordering transition, in the  = 5 (001) twist boundary of a bi-crystal below the melting point, was investigated by using constant-pressure molecular dynamics simulations. This simulation permitted the grain boundary structure to be imaged at various temperatures. It was found that the equilibrium grain boundary structure at 300K retained the periodicity of the coincident site lattice, so that the lowest-energy structure corresponded to the coincident-site arrangement of the 2 ideal crystals. With increasing temperature, the total internal energy of atoms in both the perfect crystal and the grain boundary increased, as did the number of layers in the grain boundary. The grain boundary core existed, and the perfect crystal structure still existed outside of the grain boundary, at an homologous temperature of 0.9315. However, 2 atomic layers of the equilibrium grain boundary structure at this temperature lost the coincident site lattice periodicity and created a structure with liquid-like disorder. Thus, partial melting of the grain boundary occurred at an homologous temperature of above 0.9375. This was in agreement with experimental data.

J.Lu, J.A.Szpunar: Interface Science, 1995, 3[2], 143-50