arXiv subjects

Ilnaz I. Fairushin

Publications and source records attributed to Ilnaz I. Fairushin.

5 recordsLinked to original sources

arXiv2026

Frenkel line of Yukawa fluids within the self-consistent relaxation theory

For a simple model fluid, the Yukawa fluid, the condition for dynamic crossover, known as the Frenkel line, is defined. The condition is related to the fact that the roton minimum in the dispersion relation of longitudinal acoustic-like excitations exists only when the collective vibrational dynamics of particles dominates in the liquid. Based on the self-consistent relaxation theory for the Yukawa fluid, thermodynamic states are determined in which the roton minimum disappears. The obtained values of the state parameters for the Frenkel line are consistent with the results of studies in which the position of this line on the phase diagram of the Yukawa fluid was determined using molecular dynamics simulations. It is shown that the Frenkel line in this system can be determined directly from the structural characteristic -- the static structure factor. A physical interpretation of the roton minimum frequency for the simple liquids near the Frenkel line is proposed.

cond-mat.stat-mech↗

arXiv2025

Weak decaying collective-excitation approximation for Yukawa one-component plasmas

In this paper, the theoretical model of weak decaying collective excitations characteristic of many-particle systems with long-range interaction potentials is developed using the example of one-component strongly coupled Yukawa plasmas. The proposed model is based on the self-consistent relaxation theory of collective dynamics and covers spatial scales from extended hydrodynamics to scales related to the mean interparticle distance. The theoretical model reproduces the dynamic structure factor spectra and the corresponding dispersion characteristics in agreement with molecular dynamics simulation data without using any fitting parameters. In the limit of small wave numbers, the correspondence of the proposed theoretical model with the damped harmonic oscillator model is established. The simple analytical expression for the sound attenuation coefficient of strongly coupled Yukawa plasmas is obtained.

physics.plasm-ph↗

arXiv2023

Collective ion dynamics in Coulomb one-component plasmas within the self-consistent relaxation theory

In this paper, we present the theoretical formalism describing the collective ion dynamics of the nonideal Coulomb classical one-component plasmas on the basis of the self-consistent relaxation theory. The theory is adapted to account for correlations between the frequency relaxation parameters that characterize the three- and four-particle dynamics and the parameters associated with the two-particle dynamics. The dynamic structure factor spectra and dispersion characteristics calculated for a wide range of wave numbers are in agreement with the molecular dynamics simulation data and the results obtained with the theory of the frequency moments. The proposed formalism reproduces all the features inherent to the Coulomb one-component plasmas and requires only knowledge of the coupling parameter and the information about the structure.

physics.plasm-ph↗

arXiv2023

Calculation of Thermodynamic Characteristics and Sound Velocity for Two-Dimensional Yukawa Fluids Based on a Two-Step Approximation for the Radial Distribution Function

We propose a simple two-step approximation for the radial distribution function of a one-component two-dimensional Yukawa fluid. This approximation is specified by the key parameters of the system: coupling parameter and screening parameter. On the basis of this approximation, analytical expressions are obtained for the same thermodynamic quantities as internal energy, internal pressure, excess entropy in the two-particle approximation, and also longitudinal sound velocity. The theoretical results show an agreement with the results obtained in the case of a true radial distribution function.

cond-mat.stat-mech↗

arXiv2022

Self-Consistent Relaxation Theory of Collective Ion Dynamics in Yukawa One-Component Plasmas under Intermediate Screening Regimes

The self-consistent relaxation theory is employed to describe the collective ion dynamics in strongly coupled Yukawa classical one-component plasmas. The theory is applied to equilibrium states corresponding to intermediate screening regimes with appropriate values of the structure and coupling parameters. The information about the structure (the radial distribution function and the static structure factor) and the thermodynamics of the system is sufficient to describe collective dynamics over a wide range of spatial ranges, namely, from the extended hydrodynamic to the microscopic dynamics scale. The main experimentally measurable characteristics of the equilibrium collective dynamics of ions -- the spectrum of the dynamic structure factor, the dispersion parameters, the speed of sound and the sound attenuation -- are determined within the framework of the theory without using any adjustable parameters. The results demonstrate agreement with molecular dynamics simulations. Thus a direct realization is presented of the key idea of statistical mechanics: for the theoretical description of the collective particle dynamics of equilibrium fluids it is sufficient to know the interparticle interaction potential and the structural characteristics. Comparison with alternative or complementary theoretical approaches is provided.

physics.plasm-ph↗