Islandlike in-plane structure and vibrational behavior ofNiCl2intercalated in graphite

Accurate extended x-ray-absorption fine-structure (EXAFS) measurements, at room temperature, have been made on nickel dichloride single crystals and on the same compound intercalated in graphite, in order to study the vibrational and structural properties of the latter low-dimensional system. EXAFS spectra have been performed both on the K edge of Ni and on the K edge of Cl. The ${\mathrm{NiCl}}_2$ molecules intercalated between the hexagonal planes of graphite form clusters or islands, about 10 Å apart on the same layer, with a Ni triangular lattice incommensurate with the graphite host lattice. However, in spite of the expected distortion of the intercalated compound, our results indicate that the ${\mathrm{NiCl}}_2$ molecule exhibits no deformation upon intercalation with respect to the pristine crystal. A theoretical simulation of the EXAFS spectra of the single crystal has confirmed the recent diffractional parameters reported in the literature.