Abstract
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, τc. Differences between the core structures and glide planes of the 1/2111 screw
dislocation for the two potentials do not affect τc in this temperature range. The only significant
difference between the dislocation–void interactions in the two models occurs at low
temperature in static or pseudo-static conditions (T 1 K). It arises from the influence of the
dislocation segment in the 70◦-mixed orientation with the (Ackland et al 2004
J. Phys.: Condens. Matter 16 S2629) potential and is seen in the critical line shape at which the
dislocation breaks from the void. It affects τc for some combinations of void size and spacing.
The effect on the line shape does not arise from anisotropy of the elastic line tension: it is due to
the high Peierls stress of the 70◦ dislocation. When this effect does not control breakaway, the
dependence of τc on void size and spacing follows an equation first found by modelling the
Orowan process in the approximation of linear elasticity.