Quantum chemical and x-ray spectral studies of the structures of superstoichiometric fluorocarbons

The possibility of hole formation in the structures of superstoichiometric fluorocarbons is studied. Different geometries are modeled by removing one, two, or six CF groups from the stoichiometric fluorocarbon lattice. The positions of fluorine atoms in the internal CF₂ groups are optimized using the semiempirical MNDO method. The quantum chemical calculations of fluorocarbon clusters containing holes of different geometries suggest the preferential formation of six-center hole structures in fluorocarbon lattices. The X-ray emission CK_α-spectra of the superstoichiometric CF_x (x=1.20 and 1.33) samples are obtained. Based on the cluster calculations, theoretical CK_α-spectra of CF_x are constructed. A comparison of the theoretical and experimental results shows that the spectra of the superstoichiometric fluorocarbons are characterized by a short-wave maximum, whose intensity increases with x. Deceased Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 6, pp. 1072–1080, November–December, 1996. Translated by I. Izvekova