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artículo con referato
"Equilibrium and Dynamical Characteristics of Imidazole Langmuir Monolayers on Graphite Sheets"
Javier Rodriguez, M. Dolores Elola and D. Laria
J. Phys. Chem. B 119(29) (2015) 9123-9128
Using molecular dynamics techniques, we examine structural and dynamical characteristics of liquid-like, Imidazole(Im) monolayers physisorbed onto a planar graphite sheet, at T = 384 K. Our simulation reveals that molecular orientations in the saturated monolayer exhibit a bistable distribution, characterized by an inner parallel arrangement of the molecules in close contact with the substrate and a slanted alignment, in those lying in adjacent outer locations. Compared to the results found in three dimensional, bulk phases, the analysis of the spatial correlations between sites participating in hydrogen bonding shows a clear enhancement of the intermolecular interactions, which also leads to stronger dipolar correlations. As a result, the gross structural features of the monolayer can be cast in terms of winding, mesoscopic domains, comprising units articulated via hydrogen bonds, that persist along typical time intervals of a few tens of picoseconds. On the dynamical side, a similar comparison of the characteristic decorrelation time for orientational motions shows a fourfold increment. Contrasting, the reduction of the system dimensionality leads to a larger diffusion constant. Possible substrate-induced anisotropies in the diffusive motions are also investigated.
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