SYMMETRY-BREAKING AND ITS INFLUENCE ON THE CORRELATION-ENERGY FOR CF4+ AND CF3(2)+ IONS

We have studied symmetry breaking in three open-shell systems: CF4+ (D 2d and C2nu) and CF3(2+) (D3h) molecular ions. These different Hartree -Fock solutions are employed as starting points to calculate the corre lation energy of these ions with perturbative, configuration interacti on, and density functional methods. When symmetry-broken or symmetry-a dapted wave functions are used, the correlation energy obtained with e ach method changes the order of stability of CF4+ for a determined sym metry. Density functional methods produce higher correlation energies although they do not alter the order of stability of Hartree-Fock calc ulations. The behavior of correlation energy with different methods an d the characteristics of the symmetry of wave functions are compared. A study of appearance energies for three different channels of the dec omposition reaction of ionized carbon tetrafluoride are considered by using different methods with symmetry-broken or symmetry-adapted wave functions to calculate correlation energies. (C) 1994 John Wiley & Son s, Inc.