ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
Bragg intensities from neutron and X-ray diffraction data of C60 single crystals were used to determine the nuclear- and electron-density distributions of C60 at room temperature. The anisotropic density distribution is reconstructed by the maximum-entropy method and evaluated in terms of symmetry-adapted spherical harmonics. From this analysis, the orientational probability density function f(ω) has been calculated and the rotational potential V(ω) that is experienced by a C60 molecule in the cubic surrounding at 295 K has been obtained. f(ω) shows strong deviations from the uniform orientational probability density function that would result from isotropic rotation. Accordingly, V(ω) exhibits well developed minima. The absolute potential minimum is found at an Euler-angle set ω1 and a second set of minima at slightly higher energy at ω2. The potential difference between V(ω1) and V(ω2) is 313 K, whereas the overall rotational potential barrier height amounts to 522 K. ω1 and ω2 are comparable with the major and minor orientations that are adopted by the molecules in their low-temperature arrangement. The angles ω1 and ω2 are fixed by the intrinsic geometry of the Euler-angle space (α, β, γ) under the combined action of the cubic site and the icosahedral molecular point group.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0108767395012566
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