It was noted that construction of the γ-surface required the application of mechanical constraints so that the energies of non-equilibrium fault configurations could be calculated. The choice of mechanical constraints was not unique and it was shown that γ-surfaces which were constructed using different schemes could differ significantly. The measurement of planar fault energies using transmission electron microscopic techniques was also critically assessed. It was discovered that the constraining effect of bounding partial dislocations could significantly modify the local fault energy. Experimentally measured fault energies were therefore expected to differ from atomistically calculated values.

A Critique of Some of the Concepts Regarding Planar Faults in Crystals. A.H.W.Ngan: Philosophical Magazine Letters, 1995, 72[1], 11-9