P. Lazar, E. Otyepková, F. Karlický, K. Čépe, M. Otyepka: The surface and structural properties of graphite fluoride, CARBON, In press, 2015.
DOI: 10.1016/j.carbon.2015.07.064, IF = 6.196
Abstract: The structural properties of graphite fluoride are not well characterized despite many experimental and theoretical studies. Computational investigations have indicated the existence of several possible stacking sequences for this material, but the methods used were incapable of adequately describing the dispersive interactions between graphite-like layers. We studied the structural and surface properties of graphite fluoride using the random phase approximation method, which provides dispersive (van der Waals) interactions with the correct asymptotic decay. The chair conformation with the AA stacking sequence is predicted to be the most stable structure, having lattice parameters of a = 2.58 Å, and c = 5.75 Å. The energetic difference between AB and ABC stacking is small, so a statistical ensemble of several stacking arrangements can be expected in graphite fluoride samples. The energy needed for the exfoliation of graphite fluoride into individual CF layers is 190 mJ/m2, which is lower than the corresponding energy for graphite. The predicted surface energy of graphite fluoride is 100 mJ/m2. We also measured the surface energy of graphite fluoride powder experimentally using inverse gas chromatography, yielding a value of 79 +/- 7 mJ/m2 that agreed well with the computational result.