GEOMETRY AND ORIENTATION OF MOLECULES IN A GRAPHITE FLUORIDE MATRIX

Polarization dependences of the EX IFS and XANES spectra of graphite f luoride intercalation compounds C2Fx .gamma A (x approximate to I, A = Br-2, Fe(AA)(3), FeCl3, SnCl4; AA = acetylacetonate) synthesized by d iffusion from solution were measured. The measurements were carried ou t in the FeK-, BrK-, and SnK-edge of absorption spectral regions using synchrotron radiation of the VEPP-3 storage ring (Institute of Nuclea r Physics, Siberian Branch, Russian Academy of Sciences). The polariza tion dependences of effective coordination numbers and edge sigma-reso nance intensity are analyzed and parameters of the local surroundings of atoms (coordination numbers, interatomic distances, Debye-Waller fa ctors sigma(2)) are determined For the Br-2 intercalates, the orientat ion angle with respect to the matrix layers is 64+/-1.5 degrees, and t he interatomic distances are close to those in the gas phase. The FeCl 3 molecule forms dimers in the matrix as it does in the gas phase, and the iron atoms have tetrahedral surroundings. For the Fe(AA)(3) molec ules intercalated into the matrix, the iron atoms have significantly d istorted octahedral environments. For the SnCl4 intercalates, the lowe ring of temperature does not cause additional coordination of Sn atoms and structural disorder of SnCl4 makes the major contribution to sigm a(2).