Generalized stacking fault energies and ½<111> screw dislocation core structures were reported for two sets of models for iron: density functional theory calculations and empirical potentials. A thorough comparison between various density functional theory approaches was performed on {110} and {211} γ-lines, which give a first indication on dislocation properties: (i) the effect of the exchange-correlation functional, LDA versus GGA, was significant in the pseudopotential approximation but not in the PAW approximation or in paramagnetic calculations; and (ii) the discrepancy due to the basis set between SIESTA and plane-wave results was rather small. Three empirical potentials for iron were benchmarked on these density functional theory results. They all yield similar energies, but different shapes for the γ-lines. Using the criterion suggested by Duesbery and Vitek, the γ-line results point to non-degenerate core structures for the density functional theory calculations and for the Ackland and Ackland-Mendelev potentials but not for the Dudarev-Derlet potential. The direct calculations of the dislocation core structures show that the Ackland potential was an exception to the Duesbery-Vitek rule. More insight into the stability of the core structure could be gained by looking at the response to the polarization of the core. The Dudarev-Derlet and Ackland potentials have similar polarizations, but the energy difference between degenerate and non-degenerate cores was much larger with the Dudarev-Derlet potential, as expected from the γ-lines. The polarizability of the non-degenerate core was smaller with the Ackland-Mendelev potential than in density functional theory, indicating that the energy landscape was flatter in this direction.

Generalized Stacking-Faults and Screw-Dislocation Core-Structure in BCC Iron - a Comparison between Ab initio Calculations and Empirical Potentials. L.Ventelon, F.Willaime: Philosophical Magazine, 2010, 90[7-8], 1063-74