  Point defects such as interstitial atoms are known to be attracted to screw
dislocations. Understanding these interaction mechanisms is key to predicting
the plasticity of real materials. Using a potential derived from ab initio
calculations of helium in tungsten, we find that the binding of a helium atom
to dislocation kinks is significantly more favorable than to a straight
dislocation. This preference directly translates to a reduction in the kink
pair nucleation energy, provided that the mechanism proceeds through a
helium-stabilised kink. It is lowered from 1.64 eV (in the pure metal) to 0.51
eV when helium binds to the right kink. However, binding also has a competing
effect whereby the kinks are unable to migrate. This hindering aspect becomes
more relevant as the helium concentration increases.
