Searching for Core-Level Crossings in Ir Metal*

Core-level crossings (CLC) are a novel type of transition that has been observed in Os at 440GPa, marked by an anomaly in the c/a ratio of the hcp phase and a change in the compressive behaviour. The same kind of transition is predicted in Ir at 80GPa and should be observable as an anomaly in the compression curve or the bulk modulus, but previous experimental investigations have not been able to confirm the existence of a transition due to uncertainties in the data. Indeed, the high incompressibility of Ir have motived our development of Bi as a novel pressure-transmitting medium. We have implemented this new technique, and present results from x-ray diffraction experiments up to 200PGa exploring the evidence for a CLC in Ir.