Structural Characterization of Intercalated C₂F_x Compounds Using XAFS Polarization Dependencies

Abstract
Orientation dependencies of FeK, BrK EXAFS and XANES spectra have been measured for intercalated compounds of the composition C₂F_x*yA (X≈1, A=Br₂, BrF₃, Fe(AA)₃, FeCl₃) synthesized by diffusion from solutions. An approach has been developed which allows determination of the ranges of the orientation angles of T-shaped BrF₃ molecules from XANES spectra. The values of the orientation angles of BrF₃ molecules were determined by simultaneously analyzing EXAFS and XANES data. It was found that heating leads to the formation in the intercalated compound of lens-like regions containing oriented BrF₃ molecules. The orientation and geometry of Br₂ molecules in the studied compounds were shown to be substantially different from those in graphite intercalation compounds. The intercalation was shown to lead to deformation of the Fe(AA)₃ molecule while the FeCl₃ molecules form dimers.