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Статья
2021

Calculating Stratification Curves Using a Modified Fragment Method in the Lattice Gas Model


E. S. ZaitsevaE. S. Zaitseva, Yu. K. TovbinYu. K. Tovbin
Российский журнал физической химии А
https://doi.org/10.1134/S0036024421060303
Abstract / Full Text

A numerical investigation is performed of the effect indirect correlations of nearest interacting particles have on the characteristics of stratification curves calculated within the lattice gas model. A combination of the fragment method (FM) and the quasi-chemical approximation (QCA) is used. The FM allows precise calculation of the statistical sums of configurational contributions from molecules on a small fragment with indirect correlations. The effect particles have on the state of site occupancy in a fragment as described in the QCA is considered through local external fields. A combined FM + QCA approach is used that considers external fields a calibration function for improving the accuracy of calculating thermodynamic functions with regard to indirect correlations throughout the ranges of density and temperature. It is found that allowing for indirect correlations changes the probabilities of small associates forming and lowers the critical temperature of the stratification phase transition. Calculations are made for both a square planar lattice (for which we can compare the critical and Onsager temperatures) and a cubic lattice. The calculated results are compared to similar curves in the QCA, which considers only direct correlations.

Author information
  • Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, 117901, Moscow, RussiaE. S. Zaitseva & Yu. K. Tovbin
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