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Atomic processes and strengthening effects due to interaction between edge dislocations and voids in α-iron have been investigated by means of molecular dynamics with a recently developed interatomic potential (Ackland et al 2004 J. Phys.: Condens. Matter 16 S2629) and compared with those obtained earlier with an older potential (Ackland et al 1997 Phil. Mag. A 75 713). Differences between the interactions for the two models are insignificant at temperature T≥ 100 K, thereby confirming the validity of the previous results. In particular, voids are relatively strong obstacles because for large voids and/or low temperature, the initially straight edge dislocation is pulled into screw orientation before it breaks away at the critical shear stress, τ c. Differences between the core structures and glide planes of the screw dislocation for the two potentials do not affect τ c in this temperature range. The only significant …