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Physical Review B
We determine the allowed structures for orientationally ordered icosahedral molecules on a fcc lattice such that there are four molecules per simple-cubic unit cell. The allowed space groups are Pm3, Pn3, and Pa3. In the latter two, an angle of rotation assumes a value not fixed by symmetry. The locations of all 240 atoms in the unit cell as deduced from the powder x-ray data of Heiney et al. are tabulated. We discuss a number of minima in the free energy which correspond to the observed Pa3 structure of solid C60. We introduce orientational order parameters which lead to a Landau free energy, from which we predict that the orientational transition is discontinuous.
Harris, A., & Sachidanandam, R. (1992). Orientational Ordering of Icosahedra in Solid C60. Physical Review B, 46 (8), 4944-4957. http://dx.doi.org/10.1103/PhysRevB.46.4944
Date Posted: 12 August 2015
This document has been peer reviewed.