Berlin 2012 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 60: Computational Materials Modelling IX - Interfaces and Boundaries
MM 60.6: Vortrag
Donnerstag, 29. März 2012, 18:30–18:45, TC 006
Interfacial layering of a room-temperature ionic liquid thin film on mica surfaces — •Daniele Dragoni1, Nicola Manini2, and Pietro Ballone3 — 1Theory and Simulation of Materials, École Polytechnique Fédérale de Lausanne — 2Dipartimento di Fisica, Universitá degli Studi di Milano — 3Atomistic Simulation Centre, Queen’s University Belfast.
We investigate the structure of a thin (4 nm) [bmim][Tf2N] film on mica by molecular-dynamics simulations using an empirical force field. Interfacial layering at T=300 K and at T=350 K is investigated by determining the number- and charge-density profiles of [bmim][Tf2N] as a function of distance from mica, and by computing the normal force Fz opposing the penetration of the ionic liquid film by a hard nanometric tip, represented by a spherical particle interacting with [bmim][Tf2N] atoms by a short range potential. The results show that layering is important but localized within ∼ 1 nm from the interface. The addition of a surface charge on mica, globally neutralised by an opposite charge on the [bmim][Tf2N] side, gives rise to low-amplitude charge oscillations extending through the entire film. However, outside a narrow interfacial region, the resistance of the [bmim][Tf2N] film to penetration by the mesoscopic tip is only marginally affected by the charge at the interface. The results obtained here for [bmim][Tf2N]/mica are similar to those obtained using the same method for the [bmim][Tf2N]/silica interface, and agree reasonably well with experimental force-distance profiles measured on this last interface at ambient conditions.