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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.


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.


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.


Veprev D.P.,Karpov Institute of Physical Chemistry | Muromtsev V.I.,Karpov Institute of Physical Chemistry
Astroparticle Physics | Year: 2012

The tritium decay rate has been investigated as a function of time. The 27-day and daily variations of counting rate in the high-energy region of the tritium beta spectrum have been obtained. It has been supposed that the 27-day variations could be caused by the interaction of tritium nuclei with low-energy solar neutrinos.© 2012 Elsevier B.V. All rights reserved.


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.


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.


Tovbin Yu.K.,Karpov Institute of Physical Chemistry
Russian Journal of Physical Chemistry A | Year: 2012

The problem of the lower boundary of the intrinsic linear size of the range in which the thermodynamic approach is applicable is considered. It is established that a natural constraint of any thermodynamic approach is the discrete structure of a substance at the atomic-molecular level. It is shown that with a reduction in the size of a substance, the fraction of surface particles compared to their total amount grows and spontaneous density fluctuations increase. The molecular theory of density fluctuation in small systems is discussed. Drop radii below which thermodynamic approaches cannot be used, and for which thermodynamic approaches can be used when both the discreteness of a substance and the contributions from spontaneous fluctuations can be ignored, are estimated. The consequences of the molecular theory of curved vapor-liquid interfaces are examined within the lattice gas model for spherical drops in the vapor phase. The limitations and conditions for considering corrections for density fluctuations in macrophases are discussed. © 2012 Pleiades Publishing, Ltd.


Tovbin Yu.K.,Karpov Institute of Physical Chemistry
Russian Journal of Physical Chemistry A | Year: 2014

Molecular principles of a theory of adsorbate melting near the open surfaces of adsorbents in the frozen state or in slit-shaped pores are discussed. The states of liquid and crystalline adsorbates are described in terms of a single molecular approach (the lattice gas model). The crystalline state is described using the concept of quasi-average distributions, for which the degeneracy of the density distribution function in the plane of the adsorbent is eliminated. Equations for the chemical potential of the adsorbate in defective crystals and vapor-liquid systems are derived with allowance for their vibrational motion, making it possible to calculate the concentration profile of the substance at the planar interface between two solid phases, between a solid and a liquid, and inside a slit-shaped pore. © 2014 Pleiades Publishing, Ltd.


Tovbin Yu.K.,Karpov Institute of Physical Chemistry
Russian Journal of Physical Chemistry A | Year: 2014

Problems that arise in refining calculations of the equilibrium thermodynamic functions of an adsorbate located near an adsorbent's surface or inside slit-like pores when its collective vibrational motions are considered are discussed. A technique is proposed for calculating collective vibrations for a small number of vacancies in a defective heterogeneous adsorbate from changes in the number of degrees of freedom and the local frequencies in the frequency distribution function in an ideal bulk crystal. © 2014 Pleiades Publishing, Ltd.


Lushnikov A.A.,Karpov Institute of Physical Chemistry
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2013

The formation of a gel in a disperse coagulating system, wherein binary coagulation governs the temporal changes of the particle mass spectrum is studied for the coagulation kernel proportional to K(g,l)=gl with g,l being the numbers of monomers in the coalescing pair of particles. This model is known to reveal the sol-gel transition, i.e., the formation of one giant cluster with the mass comparable to the total mass of the whole system. This paper reports on some exact results that are valid for arbitrary initial particle mass spectra. The particle spectrum is shown to be expressed through a contour integral of the exponentiated initial generating function of the particle mass spectrum. The exact formula for the gel mass is derived for the scenario of passive gelation. Two scenarios of gelation, where the gel is either active or passive, are considered. © 2013 American Physical Society.

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