AB-INITIO MOLECULAR-ORBITAL STUDIES OF THE VIBRATIONAL-SPECTRA OF NITROSYL FLUORIDE AND CHLORIDE MONOMERS AND DIMERS .2. (ONF)2 AND (ONCL)2

The optimized structures, and the infrared and Raman spectra of the dimers of nitrosyl fluoride and nitrosyl chloride have been predicted by means of ab initio molecular orbital theory, using the GAUSSIAN 86 and GAUSSIAN 88 computer programs. The calculations were carried out at both the restricted Hartree Fock and the second order Moller Plesset levels of theory, using the 6-31G* split-valence polarized basis set. The results have been compared with a similar set of calculations on the respective monomers and, in the case of nitrosyl chloride, with the Raman spectrum of the pure solid and with the infrared spectra of the solid and of nitrosyl chloride isolated in argon matrices. The energies of dimerization, internal valence force constants and atomic polar tensors, and their invariants have also been determined, and have been rationalized on the basis of the derived structures and the proposed mode of interaction.