Structure and stability of hydrogen bonds under conditions of heating in nanopores

High Temperature - The influence of heating from 260 to 400 K on the structure and mechanism of the formation of a molecular water film adsorbed on the walls of a plane fracture with the width of...     

Fluctuation statistical theory of nucleation in water vapors at near-critical temperatures

The Monte Carlo method has been used to study the evolution of the statistical behavior of density fluctuations in water vapors when approaching the critical isotherm from low temperatures. The free energy, work, and entropy of the formation of the nanosize density fluctuations have been calculated numerically. The spontaneous formation of the critical nucleus of the condensed phase is possible only against the back-ground of the density fluctuations with dimensions exceeding a certain threshold value n*, which increases rapidly when the critical temperature is approached. One should expect a qualitative change in the mechanism of the growth of nuclei of the condensed phase in the region of near critical temperatures from the statistically independent acts of the absorption of monomers by the surface of a microdroplet to the strongly correlated density fluctuations of expanding spatial dimensions.     

Computer Simulation of Water Vapor Adsorption on the Surface of a Crystal β-AgI Regular Shape Nanoparticle

Protection of Metals and Physical Chemistry of Surfaces - The Gibbs free energy and water vapor adsorption isotherms on the surface of a silver iodide nanoparticle at a temperature of 260 K have...     

Spin states of electrons in quantum dots upon heating. Simulation by the Feynman path integral method. Structure

Electrons in ellipsoidal model quantum dots under the conditions of thermal fluctuations are numerically simulated by the Feynman path integral method. This method makes it possible to perform calculations with fundamentally accurate consideration of quantum-mechanical indistinguishability of electrons and spin without applying the single-electron approximation. Electron density distributions depending on the quantum dots shape and temperature variations are obtained. An increase in temperature primarily affects the electron–electron correlations in the quantum dots central region. This influence is the main mechanism of the dependence of the spin state on temperature.     

Nucleation of water vapors at temperatures above the boiling point in the presence of ion admixtures

The dependences of the Gibbs energy, entropy, and work of formation on the sizes of the centers of nucleation of a condensed phase with the size of up to 533 molecules formed on singly charged sodium cations and chlorine anions in water vapor at the temperature of 400 K have been calculated on the molecular level by the Monte Carlo method. It has been shown that, when the detailed interaction model is used, the effect of pulling the ion from microdroplets is kept at relatively high temperatures, accelerating the loss of the thermodynamic stability of the center of nucleation and the formation of the typical nucleation barrier, the same as in homogeneous microdroplets. When ion admixtures are present, the free energy barrier to the growth of centers of nucleation in strongly supersaturated vapors is considerably lowered. The nucleation velocity and minimum relative contents of the ion admixtures, able to accelerate nucleation, have been estimated in the region of strong supersaturation.     

Adsorption on a Surface with Defects of Glassy Type: Molecular Mechanisms and Thermodynamics

Protection of Metals and Physical Chemistry of Surfaces - Computer simulation of the deposition of water vapor molecules on a rigid substrate at atemperature of 260 K are performed by the Monte...