Ab‐Initio Calculations on the Structures and Electronic States of Dimethylsulfide‐Water Clusters

Abstract

Ab initio and density functional theory (DFT) calculations have been applied to hydration processes of dimethylsulfide (DMS), which plays an important role in cloud condensation nuclei (CCN) in marine boundary layer. The molecular complexes composed of water and dimethylsulfide, DMS(H2O)n (n=0–3), were examined in the present calculations. The MP4SDQ/6‐311G(2d,p)//B3LYP/6‐311G(d,p) calculations indicated that the binding energy of H2O to DMS is calculated to be 7.7 kcal/mol for n=1. The second water molecule is bound to H2O of DMS(H2O) by a hydrogen bond, and then a 1:2 complex is formed. The binding energy of the second water molecule to DMS(H2O) was calculated to be 10.4 kcal/mol. This energy is larger than that of water dimer (the corresponding binding energy was 6.6 kcal/mol in water dimer). Direct molecular orbital‐molecular dynamics (MO‐MD) calculations were carried out for the hydration reactions DMS(H2O)+H2O→DMS(H2O)2 (1) and H2O+H2O→(H2O)2 (2) at thermal collision energy. The calculations showed that water dimer formation reaction on DMS, reaction (1), is efficiently occurred, whereas half of the trajectories for reaction (2) gave dissociation products (H2O+H2O). The mechanism of hydration of DMS was discussed on the basis of theoretical results.