title: Equilibrium and Dynamical Characteristics of Imidazole Langmuir Monolayers on Graphite Sheets.
abstract: 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 simulations reveal 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 mesoscopic domains, comprising units articulated via winding 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 4-fold 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.
authors.affiliation: †Departamento de Física de la Materia Condensada, Comisión Nacional de Energía Atómica, Avenida Libertador 8250, 1429 Buenos Aires, Argentina.|‡ECyT, UNSAM, Martín de Irigoyen 3100, 1650 San Martín, Provincia de Buenos Aires, Argentina.
authors.forename: Javier
authors.initials: J
authors.lastname: Rodriguez
authors.affiliation: †Departamento de Física de la Materia Condensada, Comisión Nacional de Energía Atómica, Avenida Libertador 8250, 1429 Buenos Aires, Argentina.
authors.forename: M Dolores
authors.initials: MD
authors.lastname: Elola
authors.affiliation: †Departamento de Física de la Materia Condensada, Comisión Nacional de Energía Atómica, Avenida Libertador 8250, 1429 Buenos Aires, Argentina.|§Departamento de Química Inorgánica Analítica y Química-Física e INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina.
authors.forename: D
authors.initials: D
authors.lastname: Laria
mesh_terms: D006108:Graphite / Q000737:chemistry*; D006860:Hydrogen Bonding; D007093:Imidazoles / Q000737:chemistry*; D056004:Molecular Dynamics Simulation
chemical_list: D007093:Imidazoles; D006108:Graphite; C029899:imidazole