  An analytical description of polymer melts and their mixtures as liquids of
interacting soft colloidal particles is obtained from liquid-state theory. The
derived center-of-mass pair correlation functions with no adjustable parameters
reproduce those computed from united atom molecular dynamics simulations. The
coarse-grained description correctly bridges micro- and mesoscopic fluid
properties. Molecular dynamics simulations of soft colloidal particles
interacting through the calculated effective pair potentials are consistent
with data from microscale simulations and analytical formulas.
