Confined thin films of linear and branched alkanes

We report computer simulations in the Grand canonical ensemble of a system of several alkanes between two solid surfaces. We computed the solvation force exerted by the fluid on the plates. The solvation force for linear decane oscillates with distance with a periodicity close to the width of the molecules. The branched alkanes (2-methylundecane and 2-methylheptane) show a similar oscillatory behavior, however the oscillations are decreased and are shifted to the attractive regime. In addition, we computed the liquid-vapour equilibria by using Gibbs ensemble Monte-Carlo simulations of n-pentane confined in a slit of 9, 13, 17 Angstrom. The critical temperature of the liquid-vapour coexistence shifts to lower temperatures upon confining. At a plate separation of 5 Angstrom, no liquid-vapour equilibrium is found. (C) 1997 American Institute of Physics.