Eur. Phys. J. B 37, 25-37 (2004)
https://doi.org/10.1140/epjb/e2004-00027-y

Single-crystal structural study of the pressure-temperature-induced dimerization of C₆₀

¹ Laboratoire de Physique des Solides, UMR CNRS 8502, bâtiment 510, Université Paris-Sud, 91405 Orsay, France
² Department of Physics, Umeå University, 90187 Umeå, Sweden
³ Laboratoire de Chimie Physique, Faculté de Pharmacie de l'Université de Tours, 31 av. Monge, 37200 Tours, France
⁴ Institute of High Pressure Physics, Russian Academy of Sciences, 142092 Troitsk, Moscow Region, Russian Federation

Corresponding author: ^a moret@lps.u-psud.fr

Received: 3 October 2003
Published online: 19 February 2004

Abstract

We present a study by Raman spectroscopy and X-ray diffraction/diffuse scattering of C₆₀ single-crystals treated at high-pressure and high-temperature. This allowed us to obtain structural information on the C₆₀ dimer state which can be considered as an intermediate state in the polymerization process. In the 1–6 GPa pressure range the crystals are primarily formed of dimers with additional minor fractions of monomers, 1D and 2D polymers, as shown by the analysis of the Raman spectra. The dimers are disordered within an average cubic lattice derived from that of the monomer. Single-crystal diffraction patterns reveal a characteristic diffuse scattering intensity distribution which has been simulated by calculating the diffuse scattering produced by dimer and trimer model structures. Satisfactory agreement is obtained for random positional and orientational disorder of the C₆₀-C₆₀ dimers although a small concentration of similarly disordered trimers is likely. In a first approximation the dimer/trimer disorder can be considered as random but various inter-dimer correlations are probably present, as discussed.