THE SYMMETRY BREAKING PROBLEM IN THE TRIFLOURIDE ANION - A MULTIREFERENCE APPROACH

摘要

The multireference MCSCF and MCSCF+MP2 methods were applied to the study of the optimum geometry of the F-3(-) anion, its vibrational frequencies and its dissociation energy into F-2+F-. The system has a strong multireference character. The optimum geometry of the F-3(-) anion doing a MCSCF(3,4) or a MCSCF(9,16) computation presents a symmetry breaking from D-infinity h-->C-infinity upsilon. Using other active spaces, like the one constructed following the orbital doubling technique, the symmetry breaking problem is solved. Finally, the accurate computation of the dissociation energy requires the inclusion of the dynamical correlation: the MCSCF dissociation energy is about 1/3 of the final MCSCF+MP2 result. The best multireference results obtained here agree very well with the best monoreference results of Heard, Marsden, and Scuseria [G. L. Heard, C. J. Marsden, and G. Scuseria, J. Phys. Chem. 96, 4359 (1992)] obtained with a QCISD(T) and similar methods. (C) 1996 American Institute of Physics. [References: 54]