Reexamination of the crystal structure of a high-pressure phase in praseodymium metal

H. K. Mao, R. M. Hazen, P. M. Bell, and J. Wittig [J. Appl. Phys. 52, 4572 (1981)] reported that praseodymium metal undergoes a crystallographic phase transformation from a distorted fcc structure to a distorted hcp structure at a pressure of ∼21 GPa. This phase change, further, is accompanied by a large volume decrease ∼19%. We have reexamined their powder diffraction data for the distorted hcp structure and find the data can be satisfactorily interpreted in terms of the well-known orthorhombic α-uranium type of structure. The volume decrease at the phase change is now estimated to be only ∼9.8%.