Water Vapor Nucleation on a Crystal Surface in a Strong Electric Field

摘要

Water vapor nucleation at 260 K in a transverse electric field has been simulated by the Monte Carlo method under conditions corresponding to an internal wall of a spatially extended microcrack in a sil- ver iodide crystal. The bicanonical statistical ensemble method has been employed to calculate, at the molec- ular level, the free energy of addition and the work of formation of dense phase nuclei in fields with different strengths. In a moderate field, the film mechanism of nucleation characterized by intense distortions on the film surface remains preserved. A domain structure of a film layer in contact with the surface exhibits a high stability with respect to an external field and remains preserved until the film is completely destroyed. In a strong electric field, the nucleation mechanism is fundamentally changed; i.e., the film is destroyed to yield threadlike structures. Therewith, the area of the contact with the surface drastically decreases. The orienta- tion of nanothreads along the electric field lines overcomes a low free energy barrier. The point of equilibrium of nanothreads with vapor depends on the presence of hydrogen bonds, while their stability is determined by longer-range dipole-dipole interactions. The observed form of existence of the condensate as polarized nan- othreads seems to be analogous to the superpolarized state previously revealed for water microdroplets, the transition to which has the character of the first-order phase transition.