Concentration dependence in NMR spectra and study of incommensurability, phase transitions and molecular dynamics in graphite intercalation compounds and zeolites

A distinct fine structure in the NMR spectra of fluorinated graphite intercalation compounds is obtained due to the selective motional averaging of the 'undesirable' intermolecular dipole-dipole interactions. Through analysis of these spectra, the arrangement of the guest molecules has been obtained. A decrease of the activation energy of diffusion with increased molecular concentration has been observed in a stage 1 sample of fluorinated graphite (C₂F)_n intercalated with acetone. These results are discussed along with similar results for Li diffusion in Li_xNbSe₃ and Li_xTiS₂ from the literature; we propose that such behavior is caused by the formation of a guest sublattice which is incommensurate with the host lattice. Unusual temperature and concentration dependences of the ¹H, ²⁰³Tl and ²⁰⁵Tl spectra in narrow-pore Tl-natrolite show that the set of positions occupied by water molecules and Tl⁺ ions changes continuously with the temperature. In this case, the water and Tl sublattice may be incommensurate with the aluminosilicate framework.