UF and the High-Pressure Polymorph HP-UF.

A laboratory-scale synthesis of UF is presented that utilizes the reduction of UF with sulfur in anhydrous hydrogen fluoride. An excess of sulfur can be removed by vacuum sublimation, yielding pure UF , as shown by powder X-ray diffraction, micro X-ray fluorescence analysis, infrared and Raman spectroscopy, as well as magnetic measurements. Furthermore, a single-crystalline, high-pressure modification of UF was obtained in a multi-anvil press at elevated temperatures. The high-pressure polymorph HP-UF was characterized by means of single-crystal and powder X-ray diffraction, as well as by magnetic measurements, and presents a novel crystal structure type. Quantum-chemical calculations show the HP-modification to be 10 kJ mol per formula unit higher in energy compared to UF .