An ab initio molecular dynamics study of diffusion, orientational relaxation and hydrogen bond dynamics in acetone-water mixtures

A theoretical study of the dynamics of water-acetone mixtures is carried out by using the methods of ab initio molecular dynamics for trajectory generation, time series analysis for frequency calculations and time correlation function approach for calculations of various dynamical quantities. It is found that diffusion coefficients and orientational relaxation times of water and acetone molecules change in a nonlinear manner with variation of composition of the mixture. The lifetimes of acetone-water hydrogen bonds are found to be shorter than that of water-water hydrogen bonds and both are found to increase with decrease of water concentration. The vibrational spectral diffusion of OD stretch modes of deuterated water molecules is also investigated for the equimolar mixture of water and acetone and the results are correlated with the dynamics of water-water and water-acetone hydrogen bonds and also of dangling OD modes. (C) 2011 Elsevier B.V. All rights reserved.