arXiv subjects

S. Yu. Ushcats

Publications and source records attributed to S. Yu. Ushcats.

3 recordsLinked to original sources

arXiv2026

Enhanced approach to calculation of cluster integrals for lattice models of matter

The study is devoted to enhancing the existing techniques of calculating Mayer's expansion cluster integrals for lattice models of matter. Two important optimizations are proposed: simplifying the calculation of the integrand at each integration point and reducing the number of such integration points due to eliminating physically identical configurations. Based on those optimizations, new data on high-order cluster integrals are obtained for a number of 2D and 3D lattice models.

cond-mat.other↗

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↗

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↗