Molecular Cycles (H O) on the Substrates with Hexagonal Crystal Structure

Formation of molecular cycles on the surface of crystalline silver iodide in contact with water vapor is simulated by the Monte Carlo method. The pictures of molecular chains and rings formed on the crystalline substrate are obtained. The stability of molecular associates under thermal fluctuations is analyzed in terms of free energy and entropy calculated from the first principles of statistical mechanics. An improved model is used to describe the molecular forces of adhesion to the crystalline substrate by taking into account long-range polarization and dispersion interactions. The field of the crystalline substrate facilitates formation of five- and six-molecule rings and prevents formation of four-molecule rings. The displacement of five-molecule rings by six-molecule rings is a collective effect requiring that a sufficient number of molecules be accumulated on the surface.