Many-body decomposition of the binding energies for OH.(H2O)2 and OH.(H2O)3 complexes

We use ab initio electronic structure methods to calculate the many-body decomposition of the binding energies of the OH.(H2O)n (n=2,3) complexes. We employ MP2 and CCSD(T) levels of theory with aug-cc-pVDZ and aug-cc-pVTZ basis sets and analyze the significance of the nonpairwise interactions between OH radical and the surrounding water molecules. We also evaluate the accuracy of our newly developed potential function, the modified Thole-type model, for predicting the many-body terms in these complexes. Our analysis of the many-body contributions to the OH.(H2O)n binding energies clearly shows that they are just as important in the OH interactions with water as they are for interactions in pure water systems.