J. Appl. Cryst. (2002). 35, 212-219 [ doi:10.1107/S0021889802000511 ]
Abstract: The crystal structure of the glass-forming molecular liquid triphenyl phosphite [TPP, P(OC6H5)3, six torsional degrees of freedom] has been solved ab initio at 110 K from powder synchrotron X-ray diffraction data by real-space methods (simulated annealing) followed by rigid-body Rietveld refinements. The symmetry is trigonal, with a rhombohedral lattice, space group 
. The associated hexagonal cell, which is a sixfold multiple of the previously published less-symmetric monoclinic cell [Hédoux et al. (1999). Phys. Rev. B, 60, 9390-9395], is unusually large [V = 7075.7 (4) Å3, Z = 18] and displays a noteworthy platelet-like shape [a = 37.766 (1) and c = 5.7286 (2) Å]. The TPP molecule does not exhibit the ideal C3 symmetric propeller shape, its conformation being on the contrary almost mirror-symmetric, with the pseudo-mirror plane passing through the P-O1 bond and two carbon atoms in para position with respect to the O1 atom. The hitherto unknown topological features of crystalline TPP, including unusual intermolecular weak C-H
O hydrogen-bonding networks, are presented and discussed in the scope of the `glacial state' problem.
Keywords: triphenyl phosphite; powder synchrotron X-ray diffraction; simulated annealing; rigid-body Rietveld refinement; low-temperature diffraction; glacial state; glass.
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