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arXiv · 1604.06827

Quasi-chemical approximation for polyatomic mixtures

M. V. Dávila·P. M. Pasinetti·D. A. Matoz-Fernandez·A. J. Ramirez-Pastor
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Abstract

The statistical thermodynamics of binary mixtures of polyatomic species was developed on a generalization in the spirit of the lattice-gas model and the quasi-chemical approximation (QCA). The new theoretical framework is obtained by combining: (i) the exact analytical expression for the partition function of non-interacting mixtures of linear $k$-mers and $l$-mers (species occupying $k$ sites and $l$ sites, respectively) adsorbed in one dimension, and its extension to higher dimensions; and (ii) a generalization of the classical QCA for multicomponent adsorbates and multisite-occupancy adsorption. The process is analyzed through the partial adsorption isotherms corresponding to both species of the mixture. Comparisons with analytical data from Bragg-Williams approximation (BWA) and Monte Carlo simulations are performed in order to test the validity of the theoretical model. Even though a good fitting is obtained from BWA, it is found that QCA provides a more accurate description of the phenomenon of adsorption of interacting polyatomic mixtures.

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M. V. Dávila, P. M. Pasinetti, D. A. Matoz-Fernandez, A. J. Ramirez-Pastor. 2016-04-22. Quasi-chemical approximation for polyatomic mixtures. https://doi.org/10.1039/c6cp03548e

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