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

Superdislocation core structures in L1₂ 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 Fe₃Ge but stable and energetically preferred in Ni₃Ge and Ni₃Al. These results allows us to suggest a mechanism for the octahedral glide being inactive in Fe₃Ge which is found to be different in several aspects with those discussed so far in the literature.