ORIENTATIONAL DISORDER IN C-60 BELOW T-S - A DIFFUSE-NEUTRON-SCATTERING STUDY

The rotational disorder in the low-temperature phase of C60 has been explored by diffuse-elastic-neutron scattering on a single crystal in the temperature range 10 K ≤T<260 K. The scattering was found to be azimuthally very anisotropic. Therefore the single-crystal data represent a rich source of information about the disorder that is complementary to the information contained in the Bragg scattering. The experimental results were analyzed using supercell calculations. Very good agreement between observed and calculated intensity patterns at T=10 K was obtained on the basis of a structure that is very close to the one proposed by David et al. The temperature dependence of the diffuse-scattering intensity confirms the conclusions drawn from diffraction data about occupancies of the majority and minority orientation. However, at T=250 K it is necessary to assume static random deviations of about 2°from the ideal orientations to obtain a satisfactory description of the data. © 1995 The American Physical Society.