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Investigation of the liquid-vapour interface of aqueous methylamine solutions by computer simulation methods

Horváth, Réka A. and Fábián, Balázs and Szőri, Milán and Jedlovszky, Pál (2019) Investigation of the liquid-vapour interface of aqueous methylamine solutions by computer simulation methods. JOURNAL OF MOLECULAR LIQUIDS, 288. pp. 1-45. ISSN 0167-7322

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Abstract

Molecular dynamics simulations of the liquid-vapour interface of water-methylamine mixtures of eight different compositions, including neat water, are performed on the canonical (N,V,T) ensemble at 280 K. The molecules constituting the first three individual molecular layers beneath the liquid surface are identified by the Identification of the Truly Interfacial Molecules (ITIM) method. The results indicate that methylamine molecules are strongly adsorbed in the first, and somewhat depleted in the second molecular layer, while the composition of the third layer agrees well with that of the bulk liquid phase. On the other hand, methylamine molecules do not show considerable self-association within the surface layer. The orientational preferences of the methyl amine molecules at the liquid surface are clearly governed by the requirement of maximizing their hydrogen bonding interaction. As a consequence, methylamine molecules point by their apolar CH3 group straight to the vapour, while by the potential hydrogen bonding directions of the NH2 group flatly to the liquid phase. Further, within the surface layer, methylamine molecules stay, on average, noticeably farther from the bulk liquid phase than waters. Increasing methylamine mole fraction leads to the gradual breaking up of the lateral percolating H-bonding network of the surface molecules. Finally, methylamine molecules accelerate, while water molecules slow down the exchange of both species between the liquid surface and the bulk liquid phase. Further, methyl amine molecules slow down the lateral diffusion of each other, and even prevent water molecules from showing noticeable lateral diffusion within the surface layer. The reason for this latter effect is that the mean residence time of the water molecules at the liquid surface becomes considerably shorter than the characteristic time of their lateral diffusion in the presence of methylamine. (C) 2019 Elsevier B.V. All rights reserved.

Item Type: Article
Additional Information: A tételhez csatolt PDF-en az eredeti kézirat címe (Methylamine solutions by computer simulation methods) látható, a metaadatok között szereplő cím a végleges kiadói változat címe.
Uncontrolled Keywords: Methylamine-water mixtures; Intrinsic surface analysis; Computer simulation; Liquid-vapour interface
Subjects: Q Science / természettudomány > QD Chemistry / kémia > QD01 Analytical chemistry / analitikai kémia
SWORD Depositor: MTMT SWORD
Depositing User: MTMT SWORD
Date Deposited: 25 Sep 2019 07:37
Last Modified: 25 Sep 2019 07:37
URI: http://real.mtak.hu/id/eprint/101075

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