Water Vapor Nucleation on a Surface with Nanoscopic Grooves. 1. Molecular Mechanisms of Adhesion

摘要

Computer simulation has been employed to study the molecular structure of condensed water nuclei growing at temperatures of 260 and 400 K from vapor on a crystalline silver iodide surface with nanoscopic straight parallel grooves having different profiles. Atom-atom spatial correlation functions have been calculated. States intermediate between the Cassie-Baxter and Wenzel states have been observed in the computer images of condensate nuclei. Nucleation begins from uptake of vapor molecules on nanogroove walls. Then, the nuclei grow toward nanogroove bottom; after that, they propagate outside of the grooves to cover the intergroove space. The field of the grooves causes intense rupture of intermolecular hydrogen bonds, thereby decreasing the degree of clustering at an initial stage of the uptake. The nanogroove-containing surface has a region of conditions for the inverse pattern of the temperature dependence of the degree of clustering of adsorbed molecules due to the low entropy of the bonds between the molecules and groove walls. The grooves facilitate the retention of the nuclei at the initial stage; however, they seem to hinder the crystallization at the final stage of the nucleation.