  We analyze the crystallization and collapse transition of a simple model for
flexible polymer chains on simple cubic and face-centered cubic lattices by
means of sophisticated chain-growth methods. In contrast to bond-fluctuation
polymer models in certain parameter ranges, where these two conformational
transitions were found to merge in the thermodynamic limit, we conclude from
our results that the two transitions remain well-separated in the limit of
infinite chain lengths. The reason for this qualitatively distinct behavior is
presumably due to the ultrashort attractive interaction range in the lattice
models considered here.
