Superdislocation core structure in L12 Ni3Al, Ni3Ge and Fe3Ge: Peierls–Nabarro analysis starting from ab-initio GSF energetics calculations

Superdislocation core structures in L1 2 Ni3Ge, Fe3Ge and Ni3Al were determined on the basis of ab-initio generalized stacking fault (GSF) energetics calculations. Superdislocation dissociation schemes, partials separation and core widths were calculated within the modified Peierls–Nabarro (PN) model with ab-initio GSF parameterization. Calculated superdislocation core structure parameters were found to be in agreement with available experimental data. The superdislocation core with type I (fourfold) dissociation was found to be unstable in Fe 3Ge but stable and energetically preferred in Ni3Ge and Ni3Al. These results allows us to suggest a mechanism for the octahedral glide being inactive in Fe 3Ge which is found to be different in several aspects with those discussed so far in the literature.  2002 Acta Materialia Inc. Published by Elsevier Science Ltd.