A study of the weak interaction in SCO/He and SCO/N2 systems

The structure and energetics of the complexes formed between SCO/He and SCO/N2 were investigated using ab initio wave functions at both the SCF and correlated levels of theory with a medium‐sized polarized basis set. The energy of the T‐structure for SCO ⃛He was found to be lower than the energy of the corresponding linear complexes with He bonded to the oxygen or sulfur atoms. Two linear structures for SCO ⃛ He were found to be nearly isoenergetic. There is only a small difference in energy between the T‐structure for SCO ⃛N2 and the OCS ⃛NN colinear structure, with the T‐structure being the lowest. The electron correlation contributions to the interaction energy were calculated using Möller–Plesset perturbation theory at the MP2, MP3 and SDTQ–MP4 levels. Analysis shows the importance of the triple excitations in these complexes.