The Adsorption of Non-polar Gases on Alkali Halide Crystals. IV Calculations of the Adsorption Behaviour of Non-polar Gases on Cubic Potassium Chloride and Cubic Potassium Bromide

Abstract

Abstract The potential energy of each isolated atom or molecule (argon, nitrogen, or carbon dioxide) adsorbed on the (100) plane of cubic potassium chloride and cubic potassium bromide has been theoretically calculated at four representative positions on the surface. According to the present theoretical calculations, it seems reasonable to consider that the high initial heat of adsorption experimentally found for nitrogen or carbon dioxide is mainly attributed to the quadrupole interaction of each molecule with the surface of the crystals. The present results suggest that the surface may be influenced by the different types of the surface heterogeneity due to the defects of the crystals and the distribution of sites grouped in patches. The present theoretical calculations also suggest that adsorbed atoms or molecules of these non-polar gases easily migrate two-dimen-sionally. These results on the surface migration are qualitatively in good agreement with the experimental entropy curves.