Application of factorial design for the ab initio study of cis- and trans-1,2 dihaloethylene stabilities

The chemometric technique Two Level Factorial Design was used to evaluate t he principal and interaction effects of wave function modifications on calc ulated energy differences (Delta E) between the cis and trans isomers of 1, 2-dihaloethylenes, C2H2X2 (X=F and Cl). The factorial profile of Delta E is quite different for these systems. The addition of polarization and diffus e functions to the basis set have the largest effects in describing cis 1,2 -difluoroethylene as the most stable isomer. In contrast electronic correla tion, 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 s table one in the 1,2-dichloroethylenes. In both systems the interaction eff ects are smaller than the principal effects.