Comparison of shear flow of hexadecane in a confined geometry and in bulk

We examine the shear flow of hexadecane confined between plates with separation of 1-10 nm using molecular dynamics simulations. We also performed non-equilibrium molecular dynamics (NEMD) simulations of bulk hexadecane to compare with the simulations in the confined geometry. The stiffness of hexadecane and its high melting temperature result in a tendency to crystallize at room temperature or large load. We find that when confined between hydrocarbon walls, shearing hexadecane exhibits a velocity profile with substantial slip at the wall and essentially constant velocity over most of the interior space between the walls. As the strength of the wall-fluid interaction increases the amount of slip decreases, but slip always occurs at the boundary for the range of parameters studied. The results are compared with recent surface force apparatus experiments on hexadecane and with similar simulations of model bead-spring fluids. (C) 1997 American Institute of Physics.