  We perform a large-scale statistical analysis (> 2000 independent
simulations) of the elongation and rupture of gold nanowires, probing the
validity and scope of the recently proposed ductile-to-brittle transition that
occurs with increasing nanowire length [Wu et. al., Nano Lett., 12, 910-914
(2012)]. To facilitate a high-throughput simulation approach, we implement the
second-moment approximation to the tight-binding (TB-SMA) potential within
HOOMD-Blue, a molecular dynamics package which runs on massively parallel
graphics processing units (GPUs). In a statistical sense, we find that the
nanowires obey the ductile-to-brittle model quite well; however, we observe
several unexpected features from the simulations that build on our
understanding of the ductile-to-brittle transition. First, occasional failure
behavior is observed that qualitatively differs from that predicted by the
model prediction; this is attributed to stochastic thermal motion of the Au
atoms and occurs at temperatures as low as 10 K. In addition, we also find that
the ductile-to-brittle model, which was developed using classical dislocation
theory, holds for nanowires as small as 3 nm in diameter. Finally, we
demonstrate that the nanowire critical length is higher at 298 K relative to 10
K, a result that is not predicted by the ductile-to-brittle model. These
results offer practical design strategies for adjusting nanowire failure and
structure, and also demonstrate that GPU computing is an excellent tool for
studies requiring a large number independent trajectories in order to fully
characterize a system's behavior.
