The Structure of Eu-III
  Previous x-ray diffraction studies have reported Eu to transform from the hcp structure to a new phase, Eu-III, at 18 GPa. Using x-ray powder diffraction we have determined that Eu remains hcp up to 33 GPa, and that the extra peaks that appear at 18 GPa are from an impurity phase with space group R-3c . Above 33 GPa the diffraction pattern becomes very much more complex, signalling a transition to a phase with a distorted hcp structure. 
R. J. Husband, I. Loa, G. W. Stinton, S. R. Evans, G. J. Ackland and   M. I. McMahon
cond-mat.mtrl-sci