Planar fault energies for a number of L12 intermetallic compounds were calculated by using  ab initio  quantum mechanics. It was shown that, in conjunction with a diagram that indicated elastic and antiphase-boundary anisotropies, such calculations could be used to predict the occurrence of a yield-strength anomaly. The less-common normal yield behavior of Pt3Al was shown to have a different origin to that previously thought. It was possible to estimate the size of the dissociated core of screw super-dislocations. Microscopic factors which determined the fault energy were identified, and the faults were separated into those whose energy was chemical in origin and those whose energy was structural in origin. The axial Ising model was used to analyze structural fault energies. It was found that there was a marked difference between the properties of Ni3Si and Ni3Ge, and this was shown to arise because the bonding was more ionic in Ni3Si and more covalent in Ni3Ge. In spite of these large differences, both of them exhibited a marked yield anomaly.

The Role of Planar Fault Energy in the Yield Anomaly in L12 Intermetallics A.T.Paxton, Y.Q.Sun: Philosophical Magazine A, 1998, 78[1], 85-103