Nucleation of Condensed Phase in Water Vapor on the Nanostructured Surface of a -AgI Crystal. 2. Free Energy

The free energy and work of nucleation of condensed water phase from vapor on a nanostructured basal face of a silver iodide crystal at 260 and 400 K have been calculated from the first principles of statistical mechanics by the Monte Carlo bicanonical statistical ensemble method. Relatively large structural elements have been represented by regularly repeating truncated pyramids with a base size of 8 nm and a height of 3nm. For the interactions, a detailed model has been employed, which comprises the Ewald summation of long-range electrostatic and polarization interactions with the substrate. The dependences of the free energy and work of nucleation on the sizes of nuclei have been compared with the corresponding dependences for a smooth basal face of the crystal. Surface nanostructuring increases the thermodynamic stability of the nuclei by an order of magnitude and extends the process of their growth by five to six orders of magnitude to the region of lower pressures. Relatively large sizes of the nanostructure elements promote a decrease in the free energy of the uptake of water molecules at an initial stage of nucleation.