The Brunauer-Emmett-Teller Equation and the Effects of Lateral Interactions. A Simulation Study

Adsorption/desorption on a smooth surface is studied at the molecular level by new, simple two-dimensional Monte Carlo simulation procedures using site-specific adsorption/desorption probabilities. The classical BET conditions are simulated and the resulting adsorption isotherms show a very good fit with the calculated theoretical parameters of the equation. The BET islands are visualized and analyzed. Following this test simulation, lateral interactions are added, resulting in type II and type III isotherms. The ensuing deviations from BET behavior are identified and analyzed. It is shown that accurate surface area values can only be obtained from an unequivocal B-point. The effects of changes in adsorption/desorption probabilities on the isotherm shapes are identified and discussed. The changes in the heat of adsorption with coverage are analyzed. It is found that this type of plot is a very sensitive analytical tool for locating the monolayer value.