X-ray diffraction study of elemental thulium at pressures up to 86 GPa

We have performed a high-pressure synchrotron x-ray diffraction experiment on elemental thulium in a diamond anvil cell to 86 GPa. A series of phase transitions was observed as a function of pressure that follow the expected hexagonal-close-packed{yields}Samarium-type{yields}double hexagonal-close-packed{yields}distorted distorted face-centered cubic sequence. In particular, we present evidence for the predicted double hexagonal close packed{yields}distorted face-centered cubic phase transition near 68 GPa. Equation of state data for thulium are also reported up to 86 GPa.