- Model calculations of the thermal collision rate densities between CO2 molecular clusters consisting of 1 to 13 monomers are presented. Cluster morphologies are chosen according to the minimal-energy configurations of Hoare and Pal and the attractive part of the intercluster potential energy is calculated by summing dipole-induced dipole interactions to all orders. To model the collision rate density for each pair of clusters, an average is taken over the rates for four orientations computed in body-fixed coordinates. Results of these calculations have implications for the interpretation of experimental results on nucleation, cluster growth, and cluster mass-frequency distributions. © 1986 American Chemical Society.