Water vapor nucleation on an infinite substrate with complementary structure: 1. The mechanism of nucleation

The nucleation of water vapor on the infinite surface of a silver iodide crystal at 260 K is simulated. Long-range electrostatic and polarization interactions are taken into account by the Ewald method. The free energy and work of equilibrium formation of nuclei are calculated at the molecular level by the method of bicanonical statistical ensemble. It is shown that, at the initial stage, the substrate is completely covered with a water monolayer. The substrate tends to decrease by two orders of magnitude the vapor pressure required to form the critical nucleus of a monomolecular film with a size of 10² molecules, the nucleation rate being increased by tens of orders of magnitude as compared to homogeneous nucleation. The saturation pressure above the adsorbed monomolecular film is 12 times lower than that above the flat ice surface. The free energy at the edges of “spots” per unit length is 1.4 × 10^?11 J/m. The critical size of the spot increases with a decrease in vapor pressure as the inverse second power of the logarithm of pressure.