Structure analysis of tantalum chloride-graphite intercalation compound using molecular simulations

Structure analysis of graphite intercalated with TaCl6- and TaOCl3 has been carried out using molecular mechanics simulations and compared to previous ly published experimental data obtained by X-ray powder diffraction, electr on diffraction, and other techniques, The basal spacing calculated for the second stage of graphite intercalated with tantalum(V) chloride c(2)(calc)= 12.80 Angstrom was in agreement with the experimental value c(2)(exp) = 12 .79 Angstrom obtained from X-ray powder diffraction, Modeling revealed the two-dimensional ordering of TaCl6- octahedra in the interlayer space of gra phite lattice. This ordered interlayer structure of TaCl6- is incommensurat e with the graphite lattice and can be described as the two-dimensional spa ce group 17pm6, hexagonal plane lattice with the lattice parameter 6.54 Ang strom. The simulated electron diffraction pattern for calculated structure was in good agreement with that seen in the experiment. The guest layer lat tice parameter obtained from electron diffraction was 6.5 Angstrom. The sim ulations gave evidence that this guest structure can be obtained only with TaCl6- octahedra as guests; other possible guests-TaCl5 dimers-can be defin itely excluded. In case of tantalum oxychloride the fragments of TaOCl3 cha in structure are arranged in the interlayer space, giving the basal spacing of the second stage c(2)(calc)= 13.39 Angstrom. (C) 2000 Academic Press.