Structure of the liquid-vapor interface of water-methanol mixtures as seen from Monte Carlo simulations

Lívia Pártay, P. Jedlovszky, Árpád Vincze, G. Horvai

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

Monte Carlo simulation of the vapor-liquid interface of water-methanol mixtures of different compositions, ranging from pure water to pure methanol, have been performed on the canonical (N, V, T) ensemble at 298 K. The analysis of the systems simulated has revealed that the interface is characterized by a double layer structure: methanol is strongly adsorbed at the vapor side of the interface, whereas this adsorption layer is followed at its liquid side by a depletion layer of methanol of lower concentration than in the bulk liquid phase of the system. The dominant feature of the interface has been found to be the adsorption layer in systems of methanol mole fractions below 0.2, and the depletion layer in systems of methanol mole fractions between 0.25 and 0.5. The orientation of the molecules located at the depletion layer is found to be already uncorrelated with the interface, whereas the methanol molecules of the adsorption layer prefer to align perpendicular to the interface, pointing straight toward the vapor phase by their methyl group. Although both the preference of the molecular plane for a perpendicular alignment with the interface and the preference of the methyl group for pointing straight to the vapor phase are found to be rather weak, the preference of the methyl group for pointing as straight toward the vapor phase as possible within the constraint imposed by the orientation of the molecular plane is found to be fairly strong. One of the two preferred orientations of the interfacial water molecules present in the neat system is found to disappear in the presence of methanol, because methanol molecules aligned in their preferred orientation can replace these water molecules in the hydrogen-bonding pattern of the interface.

Original languageEnglish
Pages (from-to)20493-20503
Number of pages11
JournalJournal of Physical Chemistry B
Volume109
Issue number43
DOIs
Publication statusPublished - Nov 3 2005

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liquid-vapor interfaces
Methanol
methyl alcohol
Vapors
Water
Liquids
water
simulation
Molecules
depletion
molecules
vapor phases
Adsorption
adsorption
Monte Carlo simulation
low concentrations
Hydrogen bonds
liquid phases
alignment
vapors

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Structure of the liquid-vapor interface of water-methanol mixtures as seen from Monte Carlo simulations. / Pártay, Lívia; Jedlovszky, P.; Vincze, Árpád; Horvai, G.

In: Journal of Physical Chemistry B, Vol. 109, No. 43, 03.11.2005, p. 20493-20503.

Research output: Contribution to journalArticle

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