Bulk moduli and high-pressure phases of the uranium rocksalt structure compounds-I. The monochalcogenides

Abstract
The high-pressure crystal structures of the compounds UX, where X = S, Se and Te, have been studied using X-ray diffraction in the pressure range up to about 60 GPa. A rhombohedral distortion is observed for US above 10 GPa. Use and UTe transform to the CsCl structure at about 20 GPa and 9 GPa, respectively. The latter transformations show a considerable hysteresis when releasing the pressure. The scaling behaviour of the bulk modulus has been studied. It is shown that a log-log plot of the bulk modulus versus specific volume for the cubic phases gives a straight line with a slope near - 2.