0.3truein Though the magnitude, width and distribution of the energy barriers are quite different for the four GB structures, the energy diagrams during the GBS show a general pattern:
1) The initial CSL structure and the final displaced structure with 100 displacement have the lowest energies;
2) Any structure between them have equal or high energies, GBS process destroys the CSL arrangement of the initial equilibrium grain boundary structure and increases the grain boundary energy. The high grain boundary energy acts as the resistance to the GBS; and
3) Energy jumps occur
at several displacement values, and there are significant energy barriers corresponding to each energy
peak.
The energy peaks (jumps) occur when the displacement is such that some atoms
in the two adjacent (hkl) planes across the grain boundary
interface (one in each of the bicrystal) are directly above (or below) each other.
Since, in general, the (hkl) interplanar spacing (all less than 0.6ae, see Figure 5) are substantially less than
the nearest-neighbor distance in
the perfect crystal (0.707ae in FCC structure), all atoms facing each other across the grain boundary
interface repel each other. In the configurations with energy peaks,
some atoms across the interface are too close to each other and hence have very high energies (refer to Figure 1).