PLANAR FAULT ENERGIES AND DISLOCATION CORE SPREADING IN B2 NIAL

We present computer simulation results for the planar faults involved in core spreading of [100] and [111] dislocations. Seven gamma surfaces were computed for different crystallographic planes ({110}, {112}, {123}, {210}, {100}, {111}, and {122}). Stable APB's are observed in the {110} and {112} planes, but they are deviated from the exact 1/2a[111] position. No other stable planar fault was observed. The fact that a stable minimum is observed deviated from the 1/2[111] position suggests the possibility of different dissociation reactions for the [111] screw dislocation in the {110} and {112} planes. The fact that no other stable minima were observed in the gamma surfaces indicates that no true core dissociation is expected for the [100] dislocations. We propose that dislocation core spreading in various planes can be understood in terms of the directions of lowest restoring forces observed for the corresponding gamma surfaces.