We have studied several microhydrated (H2O)n.NO+.H2S structures (n = 1.3) and their fragments
using wave-function based approach (coupled-clusters including single, double and
non-iterative triple substitutions . CCSD(T) and second-order perturbation theory . MP2)
and also employing density functional theory (with BLYP and .B97XD functional). MP2
energetics is very close to CCSD(T) one. Both functionals provide reasonable binding energies
compared to MP2, the .B97XD being superior to BLYP. The exploratory ab initio molecular
dynamics performed on four- and five-body clusters revealed that the hydrogen bonds
network and cooperativity in these systems play a crucial role in the proton transfer from
H2S.NO+ to H2O and its conversion to thionitrous acid.