Molecular association between water and dimethyl sulfoxide in solution: the librational dynamics of water

Molecular dynamics simulations are used to study the short-time reorientational dynamics of water in dimethyl sulfoxide (DMSO) solutions in an attempt to establish a measurable signature for a new kind of DMSO-water aggregates recently identified through MD simulations. The single-particle and collective dipole time correlation functions indicate that the reorientational dynamics of water is strongly affected in the presence of DMSO. The calculated far-infrared absorption coefficients reveal that the characteristic librational band of pure water around 700 cm(-1) is resolved in two bands in DMSO-rich mixtures due to such aggregates, thus suggesting that far-infrared spectroscopy could be used to detect these complexes in real mixtures. (C) 1998 Elsevier Science B.V. All rights reserved.