title: Properties of patchy colloidal particles close to a surface: a Monte Carlo and density functional study.
abstract: We investigate the behavior of a patchy particle model close to a hard-wall via Monte Carlo simulation and density functional theory (DFT). Two DFT approaches, based on the homogeneous and inhomogeneous versions of Wertheim's first order perturbation theory for the association free energy are used. We evaluate, by simulation and theory, the equilibrium bulk phase diagram of the fluid and analyze the surface properties for two isochores, one of which is close to the liquid side of the gas-liquid coexistence curve. We find that the density profile near the wall crosses over from a typical high-temperature adsorption profile to a low-temperature desorption one, for the isochore close to coexistence. We relate this behavior to the properties of the bulk network liquid and find that the theoretical descriptions are reasonably accurate in this regime. At very low temperatures, however, an almost fully bonded network is formed, and the simulations reveal a second adsorption regime which is not captured by DFT. We trace this failure to the neglect of orientational correlations of the particles, which are found to exhibit surface induced orientational order in this regime.
authors.affiliation: Dipartimento di Fisica, Università di Roma La Sapienza, Piazzale A. Moro 2, 00185 Roma, Italy. nicoletta.gnan@roma1.infn.it
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Gnan
authors.forename: Daniel
authors.initials: D
authors.lastname: de las Heras
authors.forename: José Maria
authors.initials: JM
authors.lastname: Tavares
authors.forename: Margarida M
authors.initials: MM
authors.lastname: Telo da Gama
authors.forename: Francesco
authors.initials: F
authors.lastname: Sciortino
mesh_terms: D003102:Colloids / Q000737:chemistry*; D009010:Monte Carlo Method; D010316:Particle Size; D011789:Quantum Theory; D013499:Surface Properties
chemical_list: D003102:Colloids