Single Crystal Structure Precludes Predicted Ferroelectricity of Uranium Trifluoride, UF3

Single crystals of uranium trifluoride, UF₃, were obtained for the first time via gas-phase crystallization, enabling the resolution of its crystal structure using single-crystal X-ray diffraction (SCXRD). The study reveals that UF₃ crystallizes isotypic to the tysonite structure type in the trigonal space group P3̅c1 (No. 165, hP24, gfda) with lattice parameters a = 7.1510(2), c = 7.3230(4) Å, and V = 324.30(³) ų, Z = 6, at T = 100 K, resolving long-standing structure model ambiguities from prior studies based on powder diffraction. Merohedral twinning complicates the diffraction data by simulating the wrong Laue class 6/mmm. Complementary quantum chemical calculations support the findings from this experiment, confirming its local energetic minimum. The inversion center in the crystal structure of UF₃ precludes the previously predicted ferroelectricity.

We have re-examined the crystal structure of UF₃ to prove its suitability as a potential ferroelectric fluoride compound. Using X-ray diffraction experiments on a single crystal, we were able to clarify the previous ambiguities about the space group in the literature and correct the space group of UF₃ to P3̅c1, which rules out its ferroelectric properties. The results are supported by quantum chemical calculations.