Structure and thermodynamic properties of water-methanol mixtures

Role of the water-water interaction

Hideki Tanaka, Keith E. Gubbins

Research output: Contribution to journalArticle

101 Citations (Scopus)

Abstract

Thermodynamic properties and structures of water-methanol mixtures at various temperatures have been investigated by means of Monte Carlo simulations and subsequent analyses. The OPLS model by Jorgensen was used for the methanol-methanol interaction and both the Caravetta-Clementi (CC) potential and TIP4P potential by Jorgensen et al. were used for the water-water interaction. We show that the role of water-water interaction is very important in discussing aqueous solutions of alcohols, and examine the origin of the exothermic mixing processes. We have investigated the sensitivity of the temperature dependence of the enthalpy of mixing to the water-water interaction. The CC potential is able to reproduce the temperature dependence observed in experiments, although the absolute values of the mixing enthalpy were larger than the experimental ones. While the TIP4P potential results in better agreement for the excess enthalpy and volume near room temperature, the temperature dependence of the excess enthalpy did not agree with experiment. The difference in the magnitude of the exothermic hydration for different water-water interactions is explained in terms of the energetic stability of the clathrate hydrate compared with ice, on the basis that the structure of water in the vicinity of a methanol molecule is similar to the clathrate hydrate. It is found that the energetic stability of the clathrate hydrate for the CC model is higher than that for TIP4P, and this is responsible for the larger exothermic hydration. The higher stability of the clathrate hydrate structure for the CC potential, in turn, arises from the difference in the pair interaction energy surface between two kinds of potential functions; the minimum energy structure and the flexibility of the hydrogen bonded pair.

Original languageEnglish
Pages (from-to)2626-2634
Number of pages9
JournalThe Journal of Chemical Physics
Volume97
Issue number4
Publication statusPublished - 1992
Externally publishedYes

Fingerprint

Methanol
Thermodynamic properties
methyl alcohol
thermodynamic properties
Water
water
clathrates
Hydrates
hydrates
interactions
Enthalpy
enthalpy
Hydration
temperature dependence
hydration
Temperature
Ice
Interfacial energy
surface energy
Hydrogen

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

Structure and thermodynamic properties of water-methanol mixtures : Role of the water-water interaction. / Tanaka, Hideki; Gubbins, Keith E.

In: The Journal of Chemical Physics, Vol. 97, No. 4, 1992, p. 2626-2634.

Research output: Contribution to journalArticle

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