It was recalled that, when epitaxial strain relief occurred via plastic deformation involving the formation of stacking faults, there were restrictions that were based upon the need to avoid non-allowed stacking sequences. A simple rule was derived here which permitted the nature of the strain relief to be determined for each of the permitted partial dislocation movements, for any orientation of an epitaxial layer. The rule was based upon the sign of the vector product,

(h•p)(h•s)

If this was positive, then the strain relief was compressive but, if it were negative, then the strain relief was tensile. Here, h was the normal to the epitaxial plane, p was perpendicular to the slip plane, and s was parallel to the slip plane.

D.W.Pashley: Journal of Crystal Growth, 1996, 162, 178-81