A STUDY OF THE WEAK INTERACTION IN SCO HE AND SCO/N2 SYSTEMS/

The structure and energetics of the complexes formed between SCO/He an d SCO/N2 were investigated using ab initio wave functions at both the SCF and correlated levels of theory with a medium-sized polarized basi s set. The energy of the T-structure for SCO ... He was found to be lo wer than the energy of the corresponding linear complexes with He bond ed to the oxygen or sulfur atoms. Two linear structures for SCO ... He were found to be nearly isoenergetic. There is only a small differenc e in energy between the T-structure for SCO ... N2 and the OCS ... N-N colinear structure, with the T-structure being the lowest. The electr on correlation contributions to the interaction energy were calculated using Moller-Plesset perturbation theory at the MP2, MP3, and SDTQ-MP 4 levels. Analysis shows the importance of the triple excitations in t hese complexes.