The work at University of Pennsylvania was supported by the National Scientific Foundation Grants DMR MRL 92-20668 and DMR 89-01219. The work at Stony Brook was supported by the NSF under Grant DMR92-02528. The SUNY X3 beamline is supported by the U.S. Department of Energy under Grant DEFG- 0291-ER45231.
Physical Review B
X-ray diffraction, Phase-transfer catalysts -- Analysis, Fullerenes -- Properties, Calorimetry, Thermal analysis
We have used differential scanning calorimetry and x-ray diffraction to study the crystalline phases of the 6,5-annulene isomer of C61H2. At 308 K the methylenated fullerenes are orientationally disordered in a face-centered cubic lattice with lattice parameter 14.19±0.02 Å. Below Tc=290 K the symmetry is lowered to Pa3¯, a simple-cubic structure. At 20 K the lattice parameter is 14.06±0.02 Å, with substantial statistical disorder remaining. The transition temperature in C61H2 is slightly higher than in C60O and higher still than in C60, but the three compounds exhibit orientationally ordering transitions between qualitatively similar phases.
Lommen, Andrea N. and Heiney, Paul A. and Vaughan, Gavin B. M. and Stephens, Peter W. and Liu, Dengfa and Li, Dayin and Smith, Allan L. and McGhie, Andrew R. and Strongin, Robert M. and Brard, Laurent and Smith, Amos B. (1994). Structure and Phase Transition of the 6,5-Annulene Isomer of C61H2. 49(18): 12572--12577.