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 C_3v 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.
  https://doi.org/10.1021/acs.inorgchem.9b00628