Clusters of SeF6 were observed in molecular dynamics simulations to undergo a solid-state transition when sufficiently undercooled. Analyses were performed on clusters ranging in size from 100 to 500 molecules to examine how faithfully properties of cores of clusters reproduce properties of bulk matter, It was found that configurational energies and coefficients of rotational diffusion of molecules in cores closely approximated those of the bulk. If this had not been true, there would have been no basis for calculating the degree of undercooling at which nucleation was observed. Excess surface energies obtained in the process were roughly half the heat of sublimation per unit area of a molecular layer and perhaps twice the surface free energy. Nucleation from the bcc phase to monoclinic was seen to occur in each of 17 cooling runs made on 150 molecule clusters. Nucleation always began in the interior of the clusters and was mononuclear, always leading to single crystals of the monoclinic phase. From the times of nucleation could be derived nucleation rates at temperatures of 88 and 78 K. Lifetimes of bcc molecules in a given orientation inferred from the runs agreed in order of magnitude with those derived from Raman and NMR spectra and yielded the same activation energy. Frequencies of rotational jumps from the old phase to the new were estimated from the coefficients of diffusion. By applying the classical theory of homogeneous nucleation, it was possible to derive the kinetic parameter sigma(ss) for the bcc-monoclinic interface. In nucleation theory it represents the interfacial free energy. This quantity was approximately 0.19 of the heat of transition per unit area from bcc to monoclinic, or about two/thirds that of the corresponding ratio proposed for freezing transitions. We conclude that clusters serve as convenient and realistic models for studying both surface properties and the dynamics of bulk systems.