Structural characterization of krypton physisorption on (0001) graphite pre-plated with cyclohexane

Abstract

The structural characterization of the composite film formed by physisorption of krypton on (0001) graphite pre-plated with a monolayer of cyclohexane has been performed by neutron and X-ray diffraction. The organization of the composite film predicted by means of volumetric measurements on a very uniform surface (exfoliated graphite) is mostly preserved on compressed exfoliated graphite (Papyex) used for diffraction experiments in spite of enhanced difficulties in reaching the adsorption equilibrium, resulting from the Papyex density. Krypton adsorption at 77 K results in the compression of the pre-adsorbed cyclohexane layer to its densest state, followed by its partial displacement and the formation of three-dimensional crystallites. The fraction of cyclohexane remaining in the adsorbed state is involved in a two-dimensional solution with krypton, of √3 x √3 commensurate structure. Beyond the first layer, krypton adsorbs on itself.