Abstract: Adsorption isotherms is the most-used way to describe adsorption phenomena. To obtain the data to construct adsorption isotherms, one can measure the amount of gas removed from the gas phase during the adsorption cycle or use other methods that allow to determine the amount of adsorbate on the surface of the adsorbent. On the other hand, in recent decades one-dimensional clusters have attracted great interest. However, one-dimensional adsorption isotherms have not yet been studied despite the fact that the one-dimensional lattice gas model has been used quite often in the study the real adsorption processes, for example in sapphire threads. In such studies, only the interactions between the nearest neighbors are usually taken into account. In this paper, one-dimensional finite-temperature monomolecular adsorption isotherms have been constructed for the first time, within the framework of the generalized Ising model. In doing so, the interatomic interactions up to the second neighbors were taken into account and the “cut-off” (free) ends were chosen as the boundary conditions – this corresponds to a free chain (cluster) or the chain on a crystal surface. A detailed analysis of how the number of sites of the atomic lattice N,interaction and temperature affect the isotherms has been performed. It was shown that within the used Ising model with the second neighbor interactions, the one-dimensional adsorption isotherms for the studied nanoclusters differ from the Langmuir isotherm. The increase in N leads to a more drastic change in the degree of filling with adatoms as a function of partial pressure (concentration of the adsorptive in the environment). At low and high pressures, the one-dimensional isotherms are practically independent of the size of the system. The initial part of the isotherm has a convexity downward (the Langmuir isotherm is always convex upwards), which indicates adatom attraction and is consistent with the traditional concepts. It is shown that the interaction of the second neighbors significantly affects the one-dimensional adsorption isotherm. With a negative interaction of the second neighbors, additional horizontal areas appear on the isotherm, which indicate the appearance of new adsorption phases.
Index terms: computer modeling, one-dimensional monomolecular adsorption, adsorption isotherms, nanoclusters, onedimensional Ising model.


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