Structural phase transitions in yttrium up to 183 GPa

Angle-dispersive x-ray powder diffraction experiments have been performed on yttrium metal up to 183 GPa.We find that the recently discoveredoF16 structure observed in the high-Ztrivalent lanthanides is also adoptedby yttrium above 106 GPa, pressures where it has a superconducting temperature of∼20 K. We have also refinedboth tetragonal and rhombohedral structures against the diffraction data from the preceding “distorted-fcc” phaseand we are unable to state categorically which of these is the true structure of this phase. Finally, analysis ofyttrium’s equation of state reveals a marked change in the compressibility upon adoption of theoF16 structure,after which the compression is that of a “regular” metal. Electronic structure calculations ofoF16-Y confirm itsstability overoF8 structure seen in Nd and Sm, and provide insight into the nature of the shift of orbital characterfromstodunder compression