To investigate whether the above observation of
cross-slip is representative of general behavior, multiple
GP zone sizes and realizations were examined. In one
of the cases, involving a 4.4 nm diameter GP zone, the
dislocation did not cross-slip, but rather overcame the
GP zone by Orowan looping [4] at a much higher applied
load, syz ¼ 280 MPa ð0:491sOrowanÞ. This occurrence
demonstrates three things. First, it shows that cross-slip
in our geometry at 0 K is sensitive to variations in the exact
atomic arrangement around the perimeter of the GP
zone (noting that at finite temperature all cases exhibited
cross-slip). Second, the critical stress required for a dislocation
to overcome a GP zone in this orientation is much
lower via cross-slip than via Orowan looping. Therefore,
for this case, cross-slip acts as a relaxation mechanism.
Third, it shows that Orowan looping can be favorable
to cutting even for nanometer-sized precipitates.1 This
point is in contrast to conventional wisdom; however,
we note that at experimental times and temperatures
thermal activation may promote cutting. No significant
correlation between GP zone size and applied stress for
cross-slip was observed for the 60 interaction.