  Interactions between an edge dislocation and a void in copper are
investigated by means of molecular dynamics simulation. The depinning stresses
of the leading partial and of the trailing partial show qualitatively different
behaviors. The depinning stress of the trailing partial increases
logarithmically with the void radius, while that of the leading partial shows a
crossover at 1 nm above which two partials are simultaneously trapped by the
void. The pinning angle, which characterizes the obstacle strength, approaches
zero when the void radius exceeds 3 nm. No temperature dependence is found in
the critical stress and the critical angle. This is attributed to an absence of
climb motion. The distance between the void center and a glide plane
asymmetrically affects the pinning strength.
