Statistical Thermodynamics of Linear Adsorbates in Low Dimensions: Application to Adsorption on Heterogeneous Surfaces

Exact forms for the thermodynamic functions of linear adsorbates in one dimension are presented in the lattice gas description of localized adsorption with multisite occupancy. A modified form of the adsorption isotherm for linear adsorbates on heterogeneous substrates is proposed, by introducing the rigorous expression for the Helmholtz free energy of the adlayer on a homogeneous one-dimensional lattice into the multisite occupancy model proposed by Nitta et al. (1984). Comparisons between the original and modified isotherms and Monte Carlo simulations for dimers and 4-mers on heterogeneous surfaces with two type of sites are carried out. Fitting of the adsorption isotherm to experimental data for CO, N 2, and O 2 on zeolites 5A and 10X is performed and discussed as well.