Structures of water clusters in the solvent phase and relative stability compared to gas phase

Abstract

Most of biological and chemical processes occur in aqueous solution. To consider this solvent effects, theoretical investigations including explicit water molecules forming clusters are often considered. These clusters have been extensively investigated in the gas phase to understand their structures, energetics, dynamics, and several other properties. However, their structures, energetics, hydrogen bond networks and many other properties in the solvent phase remained unknown. In this work, we have investigated the effects of solvent on the structures, energetics and hydrogen bond networks of the water clusters from dimer to nonamer. We have explored thoroughly the potential energy surfaces (PESs) of the considered water clusters at classical level to generate initial geometries. The generated geometries have been fully optimized in the solvent phase (represented by a dielectric continuum medium) at the MN15/6-31++G(d,p) level of theory. For the description of the dielectric continuum medium we used the integral equation formalism polarized continuum model (IEF-PCM). The results show that the hydrogen bond network in the solvent phase is different from that in the gas phase due to further interaction with the dielectric continuum medium. Several structures located in the solvent phase are found to be unstable in the gas phase. Nevertheless, we have found that the global minimum structures in both phases have the same shape although their hydrogen bond lengths are different.