Ab Initio Coupled Cluster Determination of the Equilibrium Structures of cis- and trans-1,2-Difluoroethylene and 1,1-Difluoroethylene.

The equilibrium structures of cis- and trans-1,2-difluoroethylene and 1,1-difluoroethylene, C2H2F2, have been determined with high-level coupled cluster techniques combined with large basis sets, explicit consideration of core/valence, and scalar relativistic and higher order correlation effects. Excellent agreement was found with new semiexperimental structures, increasing the level of confidence in both approaches. Differences in bond lengths among ethylene and the fluoroethylenes are discussed. [ABSTRACT FROM AUTHOR]