  We present a detailed molecular-dynamics study of the melting, freezing, and
coalescence of gold nanoclusters within the framework of the embedded-atom
method. Concerning melting, we find the process to first affect the surface
(``premelting''), then to proceed inwards. The curve for the melting
temperature vs cluster size is found to agree reasonably well with predictions
of phenomenological models based on macroscopic concepts, in spite of the fact
that the clusters exhibit polymorphism and structural transitions. Upon
quenching, we observe a large hysterisis of the transition temperature,
consistent with recent experiments on lead. In contrast, we find macroscopic
sintering theories to be totally unable to describe the coalescing behaviour of
two small clusters. We attribute this failure to the fact that the nanocrystals
are facetted, while the sintering theories are formulated for macroscopically
smooth crystallites. The time for coalescence from our calculations is
predicted to be much longer than expected from the macroscopic theory. This has
important consequences for the morphology of cluster-assembled materials.
