THERMODYNAMIC AND STRUCTURAL-PROPERTIES OF METHANOL-WATER MIXTURES - EXPERIMENT, THEORY, AND MOLECULAR SIMULATION

We report a combined experimental, theoretical and molecular simulatio n study of the thermodynamics and structure of water-methanol mixtures . FTIR spectroscopic measurements in both the fundamental and overtone regions of the O-H stretch have been made over a wide range of concen tration and temperature to obtain information on the energy of hydroge n-bonding and the concentrations of monomeric OH species. Theoretical work has been based on an extension of the cluster expansion theory of Wertheim. The FTIR measurements aid in determining the necessary inte rmolecular force parameters. The theory is used to predict the thermod ynamic properties of both pure and mixed fluids, with particular empha sis on the excess properties of the mixture. Comparisons with experime nt show moderately good agreement for this complex mixture. We also re port Monte Carlo simulations for this mixture, using OPLS potentials f or methanol-methanol and methanol-water interactions and several diffe rent potentials for the water-water interaction. We find that the resu lting excess properties are sensitive to the water-water potential cho sen. The CC potential for water gives quite good agreement with the ex perimental data.