Adsorbed /z-hexadecane films of thicknesses -10, 20, and 40 A are studied at 350 K via moleculardynamics simulations. In the thickest film periodic oscillations of the density extend to -18 A from the solid-liquid interface, the roughness fluctuations at the liquid-vapor interface are Gaussian, and the density tail is fitted by an error function. Molecules in the first adsorbed layer lie preferentially parallel to the surface exhibiting domains of intermolecular orientational alignment. The diffusion is anisotropic with the component parallel to the surface greatly enhanced in the liquid-vapor region.PACS numbers: 68.15.+e, 36.20.Ey, 61.20.Ja, 61.41.+e The structural and dynamical properties of interphase interfaces (solid to liquid and liquid to vapor) of adsorbed molecular thin films are of both fundamental and applied interest in diverse areas (such as statistical mechanics of complex fluids, thin-film boundary lubrication, and coatings) and have been the subject of recent experimental and theoretical investigations [l-6l. While early theoretical studies of interfacial systems treated mostly adsorbed simple fluids [7l more recently increased attention has been focused on molecularly complex systems.In this study we investigated, using molecular-dynamics simulations, evolutionary trends of the structure and certain aspects of the dynamics of «-hexadecane (C|6-H34) films of variable thickness adsorbed at 350 K on a crystalline substrate [modeling Au(OOl)]. In our simulations the alkane system was described via intramolecular and intermolecular interaction potentials developed previously [8], and the interaction between the pseudoatoms (CH2 and terminal CH3 segments) and the substrate atoms was taken as a 6-12 Lennard-Jones potential with a length parameter a = 3.28 A, and a well depth parameter 6=0.429 kcal/mole (which is 3 times larger than that used in describing the hexadecane system itself) determined by fitting to experimentally estimated adsorption energies [9]. The calculational cell of area equal to 3.745x10^ A^ (i.e., linear dimension of 61.2 A) was periodically repeated in the x-y directions and no periodicity was applied along the film thickness (z) direction. The static crystalline substrate was set in the geometry of a (001) gold surface consisting of three layers, with the lattice parameter of gold (the dynamics of the gold surface appears to have no discernable effect on the properties of the liquid film).The equations of motion were integrated using Gear's fifth-order predictor-corrector with a time step A/=2 xlQ-^r, where T=1.93 ps (for the thickest film M = lxl0~^r). The simulations were performed in the canonical ensemble, with the temperature controlled via infrequent scaling of particles' velocities. Following a prolonged (-10^ ps) initial equilibration stage (which involved first turning off the attraction to the substrate and subsequently allowing molecules to adsorb on the surface by turning on the attraction), each equilibrium simulation lasted for another 10^ ps. Results were average...

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