NF3 or nitrogen trifluoride is used, e.g., in the semiconductor industry to clean vapor deposition chambers. It can also be useful as a fluorination reagent or in the nuclear industry. While NF3 has been characterized using a variety of spectroscopic methods, no crystal structure had been reported so far.
Florian Kraus, University of Marburg, Germany, and colleagues have reported the crystal structures of α-NF3 and β-NF3 for the first time. The team used powder neutron diffraction at different temperatures to study the two modifications that exist at ambient pressure: α-NF3 is the low-temperature phase (studied at 6 K) and β-NF3 is the high-temperature phase (studied at 60 K).
The team found that α-NF3 crystallizes in the orthorhombic space group Pnma. The NF3 molecule has a pyramidal molecular structure in the solid state, which is in agreement with theoretical predictions. The molecule only has mirror symmetry, but is close to C3v symmetry. The two different N–F bond lengths are 1.3639 Å and 1.3677 Å, respectively. β-NF3 is a plastic crystal (i.e., and soft crystal with weak interactions) with the space group P42/mnm.
- Crystal Structures of α- and β-Nitrogen Trifluoride,
Sergei I. Ivlev, Matthias Conrad, Markus Hoelzel, Antti J. Karttunen, Florian Kraus,
Inorg. Chem. 2019.