arXiv subjects

L. A. Bulavin

Publications and source records attributed to L. A. Bulavin.

16 recordsLinked to original sources

arXiv2025

Liquid-gas state regularities as a manifestation of global isomorphism with the Ising model

Liquid-gas equilibrium is considered using the global isomorphism with the Ising-like (lattice gas) model. Such an approach assumes the existence of the order parameter in terms of which the symmetry of binodal is restored not only in the vicinity of the critical point (critical isomorphism) but also globally in the whole coexistence region. We show how the empirical law of the rectilinear density diameter of the liquid-gas binodal allows us to derive a rather simple form of the isomorphism transformation between the fluid and lattice gas model of Ising-type. The relations for critical parameters which follow from such isomorphism are tested on a variety of fluid systems, both real and model ones. Moreover, we consider the phase equilibrium in polymer solutions and the Flory $\theta$-point as the extreme state of such equilibrium within our approach. The most crucial testing in 2D case is using the Onsager exact solution of the Ising model, and we represent the results of our approach to the calculation of critical point parameters of monolayers for noble gases and the surface tension.

cond-mat.soft↗

arXiv2025

Advances of Mayer's cluster approach in quantitative theoretical description of phase transitions for various lattice models of matter

Resent achievements in statistical theory, namely, a possibility to reproduce almost unlimited Mayer's activity series based on the information about their convergence radius, on the one hand, and generalization of the lattice statistics by eliminating the simplification of nearest-neighbor interactions, on the other hand, have allowed accurate quantitative description of the condensation in lattice gases, spontaneous magnetization in ferromagnets, and spinodal decomposition in binary mixtures by evaluating only several irreducible cluster integrals (virial coefficients). In particular, the results of calculations indicate qualitative and even quantitative universality in the behavior of the mentioned lattice systems of different geometry and dimensionality at the same values of a certain reduced temperature when that behavior is expressed in terms of some dimensionless parameters. An additional possibility to describe the order-disorder phase transitions in some other lattice systems (e.g., antiferromagnets and alloys) is also discussed in the paper.

cond-mat.stat-mech↗

arXiv2020

A method to approximate cluster integrals and reproduce subcritical isotherms for model and real gases

A method is proposed to approximate the unlimited subcritical set of Mayer`s reducible cluster integrals (i.e., the power coefficients of the known virial expansions for pressure and density in powers of activity) on the basis of information about several irreducible integrals (virial coefficients) and the saturation activity. For the Lennard-Jones fluid, the first four irreducible integrals are actually sufficient to reproduce gas isotherms (including the flat phase-transition region) with high accuracy at temperatures between the triple and critical points. At low temperatures, even the usage of the first-order irreducible integral only (second virial coefficient) yields almost the same accuracy that, in turn, makes the method applicable to the real fluids with unknown interaction potential. In particular, the calculated water isotherms are in good agreement with experiments.

physics.chem-ph↗

arXiv2018

Equation of state for all regimes of a fluid: from gas to liquid

The study of Mayer's cluster expansion (CE) for the partition function demonstrates a possible way to resolve the problem of the CE non-physical behavior at condensed states of fluids. In particular, a general equation of state is derived for finite closed systems of interacting particles, where the pressure is expressed directly in terms of the density (or system volume) and temperature-volume dependent reducible cluster integrals. Although its accuracy is now greatly affected by the limited character of the existing data on the reducible cluster integrals and, especially, the absence of any information on their density dependence, a number of simple approximations indicate the qualitative adequacy of this equation in various regimes of a fluid: from gaseous to liquid states (including the transition region).

cond-mat.stat-mech↗

arXiv2017

Effect of iron oxide loading on magnetoferritin structure in solution as revealed by SAXS and SANS

Synthetic biological macromolecule of magnetoferritin containing an iron oxide core inside a protein shell (apoferritin) is prepared with different content of iron. Its structure in aqueous solution is analyzed by small-angle synchrotron X-ray (SAXS) and neutron (SANS) scattering. The loading factor (LF) defined as the average number of iron atoms per protein is varied up to LF=800. With an increase of the LF, the scattering curves exhibit a relative increase in the total scattered intensity, a partial smearing and a shift of the match point in the SANS contrast variation data. The analysis shows an increase in the polydispersity of the proteins and a corresponding effective increase in the relative content of magnetic material against the protein moiety of the shell with the LF growth. At LFs above ~150, the apoferritin shell undergoes structural changes, which is strongly indicative of the fact that the shell stability is affected by iron oxide presence.

physics.bio-ph↗

arXiv2017

MD simulation of the radiation influence on the thermophysical properties and the structure of water

The results of the molecular dynamics simulation of the radiation influence on the structure and thermophysical properties of water are presented. The changes in the radial distribution functions, momentum distribution function and the selfdiffusion coefficients are quantified. It is shown that the irradiation causes the changes in the structural and thermodynamic properties of water. The "effective temperature" of the stationary nonequilibrium water system under the irradiation allowing to define the correspondent equilibrium system with the same structural and thermodynamic properties is calculated. It is confirmed that the structural changes in the liquid systems under irradiation are caused by the changes in the coefficients of the Maxwell distribution function due to the momentum exchange between the active particles and the particles forming the liquid. To explain the phenomena observed in the molecular dynamics simulation the results are quantitatively compared to the predictions of the theoretical model of the phenomenon that is based on the Bogolyubov chain of equations and with the experimental data.

cond-mat.stat-mech↗

arXiv2016

Radiation influence on the temperature-dependent parameters of fluids

Based on the fundamental Bogolyubov chain of equations, a model relating the structural and thermophysical properties of the nonequilibrium liquid systems under irradiation in stationary state is introduced. The obtained results suggest that the thermophysical properties of the liquid systems under irradiation are defined by the {\textquotedblleft}effective temperature{\textquotedblright} that can be calculated from the perturbed momentum distribution functions of the systems. It is shown that the structural changes in the liquid systems under irradiation are caused by the changes in the coefficients of the Maxwell distribution function due to the momentum exchange between the active particles and the particles forming the liquid. To confirm the theoretical predictions, a qualitative comparison of the model with the existing experimental data on irradiation influence on the surface tension coefficients of liquids is performed.

cond-mat.stat-mech↗

arXiv2015

Curvature correction term as a constraint for the Skyrme interaction

The curvature correction term to the surface tension is used as a criterion for the efficiency of the Skyrme interaction in describing surface properties. Based on the nuclear equation of state, the curvature correction term to the surface tension coefficient is calculated for 97 standard Skyrme interaction parameter sets in the vicinity of nuclear saturation density at zero temperature. The main idea is to find those parametrizations that give the Tolman's $δ$ correction close to the available theoretical predictions from the statistical theory. Only 59 out of 97 models give satisfactory results. Comparison of the obtained results with the results of the implementation of different macroscopic and microscopic constraints to Skyrme parametrizations available in the literature allows us to select 4 models that satisfy all the constraints.

nucl-th↗

arXiv2015

Calculation of the Dimer Equilibrium Constant of Heavy Water Saturated Vapor

Water is the most common substance on Earth.The discovery of heavy water and its further study have shown that the change of hydrogen for deuterium leads to the significant differences in their properties.The triple point temperature of heavy water is higher,at the same time the critical temperature is lower.Experimental values of the second virial coefficient of the EOS for the vapor of normal and heavy water differ at all temperatures.This fact can influence the values of the dimerization constant for the heavy water vapor.The equilibrium properties of the dimerization process are described with the methods of chemical thermodynamics.The chemical potentials for monomers (m) and dimers (d)are the functions of their concentrations.The interactions of monomer-dimer and dimer-dimer types are taken into account within the solution of equation for chemical potentials.The obtained expression for the dimerization constant contains the contributions of these types.The averaged potentials are modeled by the Sutherland potential.Theoretical values of the dimerization constant for the heavy water vapor at different temperatures are compared to those for normal water.We see the exceeding of the values for the heavy water at all temperatures.This fact is in good agreement with all experimental data that is available.The excess is related to the differences in the character of the heat excitations of the dimers of normal and heavy water,their rotational constants and energy of their vibrational excitations.Significant role is also played by the monomer-dimer and dimer-dimer interactions.

cond-mat.soft↗

arXiv2014

Jamming and percolation of parallel squares in single-cluster growth model

This work studies the jamming and percolation of parallel squares in a single-cluster growth model. The Leath-Alexandrowicz method was used to grow a cluster from an active seed site. The sites of a square lattice were occupied by addition of the equal size $k \times k$ squares (E-problem) or a mixture of $k \times k$ and $m \times m$ ($m \leqslant k$) squares (M-problem). The larger $k \times k$ squares were assumed to be active (conductive) and the smaller $m \times m$ squares were assumed to be blocked (non-conductive). For equal size $k \times k$ squares (E-problem) the value of $p_j = 0.638 \pm 0.001$ was obtained for the jamming concentration in the limit of $k\rightarrow\infty$. This value was noticeably larger than that previously reported for a random sequential adsorption model, $p_j = 0.564 \pm 0.002$. It was observed that the value of percolation threshold $p_{\mathrm{c}}$ (i.e., the ratio of the area of active $k \times k$ squares and the total area of $k \times k$ squares in the percolation point) increased with an increase of $k$. For mixture of $k \times k$ and $m \times m$ squares (M-problem), the value of $p_{\mathrm{c}}$ noticeably increased with an increase of $k$ at a fixed value of $m$ and approached 1 at $k\geqslant 10m$. This reflects that percolation of larger active squares in M-problem can be effectively suppressed in the presence of smaller blocked squares.

cond-mat.dis-nn↗

arXiv2014

Evaluation of the curvature-correction term from the equation of state of nuclear matter

Based on the nuclear equation of state, the curvature correction term to the surface tension coefficient is calculated. Tolman $δ$ correction is shown to be sensitive to the Skyrme force parametrization. The temperature dependence of the Tolman length, important in heavy ion collisions experiments, is derived. In suggested approach the curvature term is related to the bulk properties of the nuclear matter through the equation of state. The obtained results are compared with the existing theoretical calculations based on the Gibbs-Tolman formalism and with the theoretical predictions concerning its dependence on the interparticle distance.

nucl-th↗

arXiv2013

Universality classes and critical phenomena in confined liquid systems

It is well known that the similar universal behavior of infinite-size (bulk) systems of different nature requires the same basic conditions: space dimensionality; number components of order parameter; the type (short- or long-range) of the intermolecular interaction; symmetry of the fluctuation part of thermodynamical potential. Basic conditions of similar universal behavior of confined systems needs the same supplementary conditions such as the number of monolayers for a system confinement; low crossover dimensionality, i.e., geometric form of restricted volume; boundary conditions on limiting surfaces; physical properties under consideration. This review paper is aimed at studying all these conditions of similar universal behavior for diffusion processes in confined liquid systems. Special attention was paid to the effects of spatial dispersion and low crossover dimensionality. This allowed us to receive receiving correct nonzero expressions for the diffusion coefficient at the critical point and to take into account the specific geometric form of the confined liquid volume. The problem of 3D \Leftrightarrow 2D dimensional crossover was analyzed. To receive a smooth crossover for critical exponents, the Kawasaki-like approach from the theory of mode coupling in critical dynamics was proposed. This ensured a good agreement between data of computer experiment and theoretical calculations of the size dependence of the critical temperature T_{c}(H) of water in slitlike pores. The width of the quasi-elastic scattering peak of slow neutrons near the structural phase transition in the aquatic suspensions of plasmatic membranes (mesostructures with the typical thickness up to 10 nm) was studied.

cond-mat.soft↗

arXiv2012

Specific Features of Motion of Cations and Anions in Electrolyte Solutions

The nature of mobility of ions and water molecules in dilute aqueous solutions of electrolytes (at most fifteen water molecules per ion) is investigated. It is shown that the behavior of the mobility coefficients of water molecules and ions, as well as the self-diffusion coefficients of water molecules, are determined by the radii of their hard shells rather than by the effect of the hydrogen bond network. It is established that the influence of hydration effects on the density of the system and the self-diffusion coefficients of water molecules does not exceed several per cent. Based on microscopic concepts, it is shown that the different behaviors of a $\rm K^{+}$ cation and an $\rm F^{-}$ anion with equal rigid radii are in good agreement with specific features of the intermolecular interaction described by the generalized Stillinger--David potential.

physics.chem-ph↗

arXiv2011

Peculiarities in the behavior of the entropy diameter for molecular liquids as the reflection of molecular rotations and the excluded volume effects

The behavior of the diameter of the coexistence curve in terms of the entropy and the corresponding diameter are investigated. It is shown that the diameter of the coexistence curve in term of the entropy is sensitive to the change in the character of the rotational motion of the molecule in liquid phase which is governed by the short range correlations. The model of the compressible effective volume is proposed to describe the phase coexistence both in terms of the density and the entropy.

cond-mat.stat-mech↗

arXiv2008

Observation of the DNA ion-phosphate vibrations

The low-frequency Raman spectra of Na-and Cs-DNA water solutions have been studied to determine the mode of counterion vibrations with respect to phosphate groups of the DNA double helix. The obtained spectra are characterized by the water band near 180 cm-1 and by several DNA bands near 100 cm-1. The main difference between Na- and Cs-DNA spectra is observed in case of the band 100 cm-1. In Cs-DNA spectra this band has about twice higher intensity than in Na-DNA spectra. The comparison of obtained spectra with the calculated frequencies of Na- and Cs-DNA conformational vibrations [Perepelytsya S.M., Volkov S.N. Eur. Phys. J. E. 24, 261 (2007)] show that the band 100 cm-1 in the spectra of Cs-DNA is formed by the modes of both H-bond stretching vibrations and vibrations of caesium counterions, while in Na-DNA spectra the band 100 cm-1 is formed by the mode of H-bond stretching vibrations only. The modes of sodium counterion vibrations have a frequency 180 cm-1, and they do not rise above the water band. Thus, the increase in intensity of the band 100 cm-1 in the spectra of Cs-DNA as compared with Na-DNA is caused by the mode of ion-phosphate vibrations.

q-bio.BM↗

arXiv2003

Interparticle interaction and structure of deposits for competitive model in (2+1)- dimensions

A competitive (2+1)-dimensional model of deposit formation, based on the combination of random sequential absorption deposition (RSAD), ballistic deposition (BD) and random deposition (RD) models, is proposed. This model was named as RSAD$_{1-s}$(RD$_f$BD$_{1-f}$)$_s$. It allows to consider different cases of interparticle interactions from complete repulsion between near-neighbors in the RSAD model ($s=0$) to sticking interactions in the BD model ($s=1, f=0$) or absence of interactions in the RD model ($s=1$, $f=0$). The ideal checkerboard ordered structure was observed for the pure RSAD model ($s=0$) in the limit of $h \to \infty$. Defects in the ordered structure were observed at small $h$. The density of deposit $p$ versus system size $L$ dependencies were investigated and the scaling parameters and values of $p_\infty=p(L=\infty)$ were determined. Dependencies of $p$ versus parameters of the competitive model $s$ and $f$ were studied. We observed the anomalous behaviour of the eposit density $p_\infty$ with change of the inter-particle repulsion, which goes through minimum on change of the parameter $s$. For pure RSAD model, the concentration of defects decreases with $h$ increase in accordance with the critical law $ρ\propto h^{-χ_{RSAD}}$, where $χ_{RSAD} \approx 0.119 \pm 0.04$.

cond-mat.stat-mech↗