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Tovbin Y.K.,Karpov Institute of Physical Chemistry
Russian Journal of Physical Chemistry A | Year: 2013

Molecular principles of the theory of melting of simple substances are considered with regard to defects caused by vacancies. Equations are derived for the chemical potential of atoms in a defective crystal with allowance for their vibrational motion, enabling the determination of coexisting phases (solid-vapor or solid-liquid) from the condition of the equality of chemical potentials. All three aggregate states of matter are described within a unified molecular approach: a lattice gas model. This makes it possible to combine a description of a cell filling with liquid, or vapor and a solid with phase differences in these states during the cell filling. N.N. Bogolyubov's concept of quasi-averages, from which the degeneration of the density distribution function in space is removed, is applied to describe the crystals. Questions as to the minimum size of the phase corresponding to the concept of quasi-averages and the criteria for the transition of a defective crystal to the frozen state are discussed. © 2013 Pleiades Publishing, Ltd. Source


Marichev V.A.,Karpov Institute of Physical Chemistry
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2011

Following the fundamental principle of minimum potential energy and using the notion of the partial charge transfer for halide ions adsorption on mercury, gallium and amalgam electrodes, we have introduced the notion of the " optimum surface electron density" It corresponds to maximums of electrocapillary curves of mercury-like metals at zero charge potentials in surface inactive electrolytes. Any reversible adsorption of surface active substances violates the optimum surface electron density and consequently decreases and shifts the electrocapillary maximum. © 2011 Elsevier B.V. Source


Tovbin Y.K.,Karpov Institute of Physical Chemistry
Russian Journal of Physical Chemistry A | Year: 2013

The correctness of using the macroscopic Gibbs phase rule in microheterogeneous systems is considered. Results from using molecular theory are discussed for a single-component substance in describing delamination and fusion on open surfaces and in the pores of a solid, along with the interfaces between three states of a substance in the bulk phase. It is established that the form of adsorption system phase diagrams is determined by the surface potential, depending on the composition and structure of heterogeneous surfaces, and is characterized by multiple first-order phase transitions. It is concluded that the thermodynamic approach to heterogeneous systems makes any microscale description of the real interface distribution of molecules less accurate, and all quasithermodynamic theories are insufficiently precise for describing small systems (adsorption systems and interfaces). © 2013 Pleiades Publishing, Ltd. Source


Marichev V.A.,Karpov Institute of Physical Chemistry
Journal of Solid State Electrochemistry | Year: 2012

We consider the essence and relation of the surface energy and surface tension of condensedmatter: which iswhich and (most important question here)-when For the first time, this consideration is based not on reversible thermodynamics but, as an approximation, on the Principle of Minimum Potential Energy, given two factors: (1) the time-dependent dynamic transformation of the potential energy of the system into the surface energy and into the surface tension (stress); (2) elasticity of structured surface layers of the liquids. © Springer-Verlag 2012. Source


Tovbin Y.K.,Karpov Institute of Physical Chemistry
Russian Journal of Physical Chemistry A | Year: 2015

Principles of the molecular statistical theory of small multicomponent drops/microcrystals in a three-dimensional bulk and in two-dimensional adsorption systems are developed. Equations of the theory are derived using the cluster approach. The theory describes discrete distributions of molecules in space (on a size scale comparable to the molecular size) and continuous molecular distributions (at short distances inside cells) upon their translational and vibrational motions. The theory provides a unified description of the equilibrium molecular distributions in three aggregate states and at their interfaces. Pair intermolecular interaction potentials (such as the Mie potential) in several coordination spheres that determine lattice structure compressibility are taken into account. For simplicity, it is considered that the sizes of mixture components are virtually the same. Structural cell distribution functions for the transition region of curved interfaces are derived. Expressions for the pressure tensor components inside small bodies are obtained, allowing us to calculate the thermodynamic characteristics of a vapor-liquid interface, including surface tension. Questions regarding the consistency between the theory of phase transitions in small systems and the traditional theory of associate (cluster) formation and the transition to systems limited in the total volume value are discussed. © 2015 Pleiades Publishing, Ltd. Source

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