Structure and Behaviour of Yb to 350 GPa

Ytterbium (Yb) metal is unusual among the lanthanide due to its divalence at ambient conditions, rather than the typical trivalence. This has multiple consequences for its behavior at high pressure, with the valence being strongly pressure-dependent and with Yb’s phase transitions sequence differing markedly from that of other lanthanides. We will study Yb up to 350 GPa to investigate the transition to the trivalent state above 200 GPa, and the onset of “normal” trivalent lanthanide behaviour. This will enhance our understanding of the pressure-dependence of lanthanide valence, underpinning future studies of compounds under pressure, in particular the synthesis of YbHx polyhydrides, for which an accurate understanding of the structure of Yb is indispensable.