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Spallation neutron and high-energy X-ray diffraction experiments have been performed to investigate the local structural changes in triphenyl phosphite (TPP) in the crystalline, glacial, glassy, and supercooled liquid phases. The hydrogen/deuterium first-order difference method shows a large increase in intensity due to additional hydrogen correlations in the crystalline spectra compared to the glass and supercooled liquid at ∼3.0 and 3.4 Å. These features are shown to be largely due to inter-phenyl ring H-C/H interactions, which are probably associated in part with the formation of weak intermolecular hydrogen bonds. The high-energy X-ray diffraction data show a decrease in correlations at 3.12 Å which is attributed to changes in C-O/P intramolecular interactions between the glacial and crystalline forms. The structural evolution of the glacial state was also measured over time using total neutron diffraction. The largest structural differences between the early glacial and crystalline states are observed at 3.0 and 4.5 Å. Moreover, as the transformation progresses, the glacial spectra cannot be adequately described as a simple mixture of supercooled liquid and crystalline components. These results suggest that changes in molecular conformation and nearest-neighbor interactions are responsible for the existence of the glacial state.

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We report for the first time, the synthesis and X-ray diffraction studies of single crystals of BeF(2). The crystals were obtained during the sublimation of amorphous BeF(2) under static reduced pressure. BeF(2) crystallizes in the chiral trigonal space group P3(1)21. A single-crystal X-ray diffraction study on these crystals shows that each of the Be atoms is bonded to four F atoms, and each of the F atoms is bonded to two Be atoms with associated Be-F bond distances of 1.5420(13) and 1.5471(13) Å, showing an almost regular tetrahedron. The infrared spectrum of these crystals recorded at room temperature shows distinct peaks around 770 and 410 cm(-1).

Spallation neutron and high-energy X-ray diffraction experiments have been performed to investigate the local structure of the glacial and supercooled liquid states in triphenyl phosphite. The observed diffraction patterns have been interpreted using a Reverse Monte Carlo modeling technique. The results show that the glacial state forms unusually weak intermolecular hydrogen bonds between an oxygen atom connected to a phenyl ring and an adjacent phenyl ring aligned in an approximately antiparallel configuration. The structure is very different from the hexagonal crystal which is characterized by two weaker hydrogen bonds between linear arrays of molecules which are offset from each other and packed in a hexamer arrangement.

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