Infrared Spectra of HF—DF Mixed Crystals and the Structure of Hydrogen Fluoride

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Abstract
The infrared spectra of HF—DF mixed crystals have been studied throughout the composition range. Unlike HF, the spectrum of pure DF shows only the two peaks in the stretching region which are characteristic of the zigzag chain structure found by x‐ray studies for HF and spectroscopically for HCl and HBr. The spectrum of pure HF shows the anomalous features previously reported. From the mixed crystal spectra it is clear that there is only one kind of site and one kind of strongly interacting pair in either HF or DF. A resolved peak due to triplets of HF (in DF) and of DF (in HF) has been observed. It is concluded that the extra peaks in pure HF probably arise from lattice combinations; in any case all of the major features of the spectra are accounted for by the zigzag chain structure of symmetry D2h16‐Pmnb. It has not yet been possible to interpret the lattice spectrum in detail.