Structures and stability of hydrated clusters of hydrogen chloride, HCl(H2O)n, n=1–5

Abstract

The molecular structures of the hydrated clusters of the HCl molecule, HCl(H2O)n, n=1–5, are examined by employing density functional molecular orbital methods. The most stable structures of the n=1–3 clusters are found to be of the proton nontransferred type. In the case of the n=4 cluster, the proton nontransferred and proton transferred structures have nearly similar energies. There are several stable isomers for the n=5 case and the structures of these isomers are found to be all proton transferred. The relative stabilities of the direct ion-pair H+Cl−(H2O)n and the indirect ion-pair H3O+(H2O)n−1Cl− are discussed in conjunction with their structures. The prediction of the IR spectra of the stable HCl(H2O)n clusters clearly indicate the large red-shifts of the H–Cl stretching and hydrogen-bonded O–H stretching frequencies.