Analytical ab initio-Based Modeling of the Adsorption Isotherm

Abstract

An analytical ab initio-based model for adsorption isotherm is presented. As input data, this model takes the adsorption Gibbs free energies of different possible coverages within a reasonably large unit cell. In this way, the lateral interactions between adsorbates and their dependence on temperature are included. The self-dependence of surface coverage is taken into account via the introduction of heterogeneity of adsorption and the use of an appropriate configurational partition function. The model reproduces the isotherm and selectivity (for binary gas mixtures) of ab initio-based grand-canonical Monte Carlo simulations. The presented isotherm has a moderated dependence on the width of the chosen ab initio unit cell, particularly for high surface loading. This isotherm seems to be a very good approximation for the grand-canonical solution, depending on the accuracy and completeness of the ab initio data.