Molecular dynamics simulation of supersaturated vapor nucleation in slit pore. II. Thermostatted atomic-wall model

Molecular dynamics simulations of nucleation of a supersaturated Lennard-Jo nes vapor in slit nanopores are carried out. In this study we extend a prev ious work [K. Yasuoka, G. T. Gao, and X. C. Zeng, J. Chem. Phys. 112, 4279 (2000)] in that the walls of the slit are treated as actual atomic walls se rving as both the confining solid surfaces and a thermostat. The walls are fixed in place in a fcc lattice structure and wall atoms are subjected to a stiff biharmonic potential thereby bounded to lattice sites. The two walls of the slit have an identical surface [fcc (100)], but different strength of attractive interaction with the vapor particles-one is strongly adsorbin g and another is weakly adsorbing. Heterogeneous nucleation of the supersat urated vapor in the slit is investigated and events of nucleus formation ar e monitored in real time. A comparison with the previous simulation (using rigid structureless walls) leads to useful insight into the influence of th e wall model to the nucleus formation. In particular, it is found that alth ough the adsorbed particles on the structureless wall diffuse faster than t hose on the atomic wall, the rate of nucleus formation on the structureless wall is actually about one order of magnitude lower. A detailed analysis o f particle and cluster-formation flux indicates that the rate of nucleus fo rmation on the wall is more sensitive to the kinetics of adsorption of gas particles onto the wall than the diffusion rate of adsorbed particles. The higher flux of cluster formation on the atomic wall is apparently due to th e higher rate of deposition of monomers onto the wall. (C) 2001 American In stitute of Physics.