Phase Stability and Electronic Structure of Iridium in the Mbar range under Shock Compression

Iridium belongs to the 5d transition metals and it is the only refractory metal with a face-centred cubic structure. The stability of its fcc structure under extreme
conditions of pressure and temperature has been debated for years and so far, only a single HP-HT melting point was experimentally detected. In addition, a
new electronic transition called core-level crossing has been predicted for Ir at around 80 GPa at room temperature and could affect its structural properties. We
propose to use the new HPLF facility available on the beamline ID24 to perform time-resolved single-pulsed X-ray Absorption Spectroscopy measurements on
shock-compressed iridium in order to: (i) characterize the presence of any solid-solid phase transition along the Hugoniot; (ii) investigate the possible occurrence
of a CLC transition; (iii) obtain an additional melting points at P and T in excess of 5 Mbar and 14000 K, respectively