Improved method for analysis of energetic heterogeneity of surfaces from adsorption isotherms

A simple and fast algorithm (IRA: improved regularization algorithm) is proposed for evaluation of the distribution of adsorption sites (centers) as a function of their adsorption energies. The experimental adsorption isotherms are used in the algorithm as initial information. In the IRA, the regularization provides reproducibility of numerical results, but also nonnegativity of the distribution function is taken into account for physical correctness of the solution. After testing on a simulated distribution, the algorithm has been applied to the treatment of the adsorption isotherm of nitrogen on the surface of maximally hydroxylated silica. The Langmuir isotherm and two isotherms, which include corrections taking into account the laterial interactions for the patchwise and random heterogeneity models, were used for the description of local equilibrium in this system. For all models the calculated distributions show two pronounced peaks.