On the nature of the interaction in ternary water-sulfur dioxide complexes

The interpretation of the intermolecular interaction energy in the ternary 2:1 and 1:2 trimers has been done. The decomposition of the total interaction energy using two- and three-body symmetry-adapted perturbation theory (SAPT) providing physically meaningful components: electrostatic, induction, dispersion and exchange terms was applied. Four (H2O)(2) center dot center dot center dot SO2 and two H2O center dot center dot center dot (SO2)(2) trimers were analyzed. We compared the contribution of the sandwich-type pair with the contribution of the hydrogen-bonded pairs to the total interaction energy of the trimer. The assumption of pairwise additivity of the interaction in the ternary mixed trimers is not correct. The three-body nonadditivity terms represent as large as ca. 18% of the total interaction energy.