GBS in (21) boundary (Figure 8)

0.3truein In the case of (21) boundary shown in Figure 8, the energy required in the initial phase of the GBS process (from 0 to a_CSL) is relatively less compared to (11) case above. A big energy jump appears when the atoms across the boundary face each other (43-48 a_CSL shear displacements). After the short jump the GBS process proceeds easily. Comparing the two cases, in (11) the magnitudes of energy barriers are less than those of (21). However, the shape of energy plot indicates that for (11) a constant shear force needs to be applied from the initial structure till the peak is reached in contrast to that of (21). We believe that though energy barriers in (21) is higher than that in (11) (2.35 eV/ compare to 3.55 eV/), external forces (e.g. thermal vibration, vacancy motion and external stress et al.) will make (21) slide easier than the latter, since the barrier occurs over a shorter displacement range.