Reinvestigation of the crystal structure of UF6 by single-crystal X-ray diffraction.

Single-crystals of hexa-fluoridouranium(VI), UF6, were obtained by sublimation. A re-refinement of the crystal structure using low-temperature (100 K) single-crystal X-ray data was carried out considering all Uij terms of the displacement parameters of the U and F atoms, leading overall to a significantly improved structural model. UF6 crystallizes in the ortho-rhom-bic space group Pnma with the F atoms forming a double hexa-gonal closest packing of ABAC stacking with U atoms in one-sixth of the voids. The UF6 mol-ecules deviate only slightly from octa-hedral point-group symmetry.