  We examine the metastable liquid phase of a supercooled gold nanocluster by
studying the free energy landscape using the largest solid-like embryo as an
order parameter. Just below freezing, the free energy exhibits a local minimum
at small embryo sizes and a maximum at larger embryo sizes which denotes the
critical embryo size. At T=660K the free energy becomes a monotonically
decreasing function of the order parameter as the liquid phase becomes
unstable, indicating we have reached a spinodal. In contrast to the usual
mean-field theory predictions, the size of the critical embryo remains finite
as the spinodal is approached. We also calculate the rate of nucleation,
independently from our free energy calculations, and observe a rapid increase
in its temperature dependence when the free energy barrier is in the order of
$kT$. This supports the idea that freezing becomes a barrierless process around
the spinodal temperature.
