The SF6 monolayer on graphite by X-ray diffraction

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Abstract
The structure of the SF6 film adsorbed on graphite has been studied from 35 to 180 K by X-ray diffraction. Below about 95 K the complete monolayer is commensurate with the (2 x 2) superstructure of the (001) graphite face; above 95 K, it becomes incommensurate, but keeps the hexagonal symmetry. These structures are definitely different from the structure of any plane of the 3D-crystal and explain the incomplete wetting of graphite by SF6. In the submonolayer domain, the 2D-condensation shown by isotherms leads to an incommensurate solid which loses coherence, and noticeably only 20 K below the 2D-critical point (168 K)