As the initially large metastable crystallites
melt, they create a population of smaller crystals.
Eventually, these crystals shrink to the radius at which
their surface energy exceeds the binding energy holding them
together and they dissociate.
The critical radius
for a face-centered cubic crystal with lattice constant *d*,
latent heat per particle *L*,
and surface tension is

The smallest metastable crystals thus allow us to set a lower limit on the surface tension of the crystal-fluid interface.

Figure 3 shows four stages in the dissociation
of a minute crystal whose radius is one lattice constant.
Very shortly after one additional sphere separates from the surface, the
remaining spheres go on their separate ways.
While we regularly observe crystals such as that in Fig. 3(a),
we do not find smaller long-lived ordered clusters.
If we identify and apply the above result for *L*,
then we can estimate a lower limit for the surface tension:
.
This value is about an order of magnitude larger than the largest
surface tension anticipated for a system with purely repulsive pairwise
interactions [25, 26, 27].
Once again, the discrepancy is naturally explained by assuming a
long-range attractive component in the pairwise interaction.

Mon Dec 2 14:09:59 CST 1996