Study of adsorption on powders by surface differential diffraction measurements. Argon on Co₃O₄

The amplitude and phase of a wave scattered by an adsorbed layer can be deduced from the modifications of the Bragg peak of the powder by adsorption. The treatment of experimental data involves the interpretation of a function of the extra intensity detected and has the advantages of an integrated intensity method. Powders containing crystallites limited by several types of faces can be studied. The Co₃O₄ sample studied is limited only by (110) and (111) faces of respective areas 11 and 27 m² g^-1. The (111) planes terminating crystallites contain oxygen covering a layer of cobalt in octahedral sites. Other possible terminating layers are ruled out for (111) planes. The structures of the bidimensional layers of argon on (110) and (111) planes are determined.