The chemometric technique Two Level Factorial Design was used to evaluate the principal and interaction effects of wave function modifications on calculated energy differences (DE) between the cis and trans isomers of 1,2-dihaloethylenes, C2H2X2 (X=F and Cl). The factorial profile of DE is quite different for these systems. The addition of polarization and diffuse functions to the basis set have the largest effects in describing cis 1,2-difluoroethylene as the most stable isomer. In contrast electronic correlation, at the MP2 level, and the inclusion of polarization functions in the basis set have the largest effects in describing the cis form as the most stable one in the 1,2-dichloroethylenes. In both systems the interaction effects are smaller than the principal effects.
factorial design; ab initio; isomers stability; 1,2-dihaloethylenes
