arXiv subjects

S. I. Sorokov

Publications and source records attributed to S. I. Sorokov.

5 recordsLinked to original sources

arXiv2019

Reference approach in theory of pseudospin systems

For theoretical description of pseudospin systems with essential short-range and long-range interactions we use the method based on calculations of the free energy functional with taking into account the short-range interactions within the reference approach in cluster approximation. We propose a consistent formulation of the cluster expansion method for quantum pseudospin systems. We develop a method allowing one to obtain within the cluster approximation an Ornstein-Zernike type equation for reference cumulant Green function of an arbitrary order. In the two-particle cluster approximation we derived an explicit expression for pair temperature cumulant Green function of the reference system. In the cluster random phase approximation we calculated and studied thermodynamic characteristics, elementary excitation spectrum, and integral intensities of the Ising model in transverse field.

cond-mat.stat-mech↗

arXiv1997

Investigation of the annealed disordered Ising systems within two-tail approximation

In the present paper an approach for investigation of the disordered two-component Ising systems with long range interaction has been suggested. Possible applications to metalic and magnetic alloys and lattice gas are considered. We have also obtained numerical results for thermodynamical properties of these models. The comparison of numerical results obtained within mean field, gaussian field and two-tail approximations are carried out.

cond-mat.stat-mech↗

arXiv1996

Correlation functions of quenched and annealed Ising systems

Spin correlation functions (up to the 3-site one) of disordered Ising model with the nearest neighbour interaction are calculated and investigated within a two-site cluster approximation for both quenched and annealed cases. The approach yields the exact results for the one-dimensional system. The long-range interaction is taken into account in the mean field approximation.

cond-mat↗

arXiv1996

Relaxation dynamics of disordered Ising model. Two-site cluster approximation

Spin relaxation in a site-disordered Ising model within master equation approach is studied. The $\vec{q},ω$-dependent susceptibility of the model is calculated and investigated. Effects described by the two-site cluster approximation and lost by the mean field approximation are discussed. Comparison of obtained results with dielectric measurements in $Cs(H_{1-x}D_x)_2PO_4$ is presented.

cond-mat↗

arXiv1996

Investigation of the Ising-type models within cluster approach

The method for calculation of the correlation functions of the Ising-type systems with short-range interaction and with arbitrary value of spin is developed within cluster approximation. For the Ising model (spin $S^z=\pm1$) the expressions for pair and ternary correlation functions within two-particle approximation in $\set{q}$-space are obtained for the hypercubic Bravais lattices. In the 1D case the exact expressions for them in the site space is obtained as well. On the basis of the Glauber equation within two-particle cluster approximation the longitudinal dynamical susceptibility $χ(\set{q},E)$ is found. In the 1D case and in the absence of external field the expression for $χ(\set{q},E)$ is exact. For the Emery-Blume-Griffiths model ($S^z=-2,0,2$) within two-particle approximation the pair correlation functions are calculated. The four-particle cluster approximation is used for calculation of static susceptibility $χ(\set{q})$ of $KD_2PO_4$ ferroelectrics.

cond-mat↗