Monte Carlo simulations of nanoconfined n-decane films

Grand canonical ensemble Monte Carlo simulations of thin films of fluid n-decane confined between two plane-parallel, structureless walls were performed using the configurational bias method. The results indicate that special attention has to be paid to the way in which configuration space is sampled. A key quantity in the study is the solvation pressure p(s(z)), which is a damped oscillatory function of wall separation s(z). The intensity of these oscillations is a consequence of both the formation of discrete molecular layers in the fluid parallel with the walls and the presence of isolated n-decane chains interconnecting neighboring layers, in that one end of the chain belongs to one layer and the other end to its neighbor. By means of Derjaguin's approximation, the solvation force from p(s(z)), which is frequently measured in experiments employing the surface forces apparatus, was calculated. The solvation force exhibits damped oscillations superimposed on a repulsive component, an effect which is ascribed to the presence of chains interconnecting neighboring fluid layers.