Eur. Phys. J. B 26, 29-34 (2002)
https://doi.org/10.1140/epjb/e20020062

X-ray scattering study of the phase transitions in crystalline fullerene-biphenyl C₆₀[(C₆H₅)₂]

¹ Laboratoire de Physique des Solides (UMR CNRS 8502) , bâtiment 510, Université Paris-Sud, 91405 Orsay, France
² Centre de Recherche Paul Pascal, Université de Bordeaux I, avenue Schweitzer, 33600 Pessac, France

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

Received: 31 August 2001
Revised: 4 December 2001
Published online: 15 March 2002

Abstract

The phase diagram of the newly synthesized mixed crystal C₆₀-biphenyl is investigated as a function of temperature by single-crystal X-ray scattering. Diffuse scattering investigations evidencing complex disorder and local order effects are presented. Two phase transitions leading to two different doublings of the high temperature unit cell are observed, at 212 K and 147 K. The first transition is attributed to the ordering of twisted biphenyls, which couples to the orientational ordering of the C₆₀ molecules as the temperature decreases. Full ordering of the C₆₀ molecules is achieved below 100 K only, in the low temperature phase. The rich phase diagram of C₆₀-biphenyl is due to the interplay between fullerene and biphenyl ordering phenomena.