Phase stability and electronic structure of iridium metal at the megabar range

Abstract

The 5d transition metals have attracted specific interest for high-pressure studies due to their extraordinary stability and intriguing electronic properties. In particular, iridium metal has been proposed to exhibit a recently discovered pressure-induced electronic transition, the so-called core-level crossing transition at the lowest pressure among all the 5d transition metals. Here, we report an experimental structural characterization of iridium by x-ray probes sensitive to both long- and short-range order in matter. Synchrotron-based powder x-ray diffraction results highlight a large stability range (up to 1.4 Mbar) of the low-pressure phase. The compressibility behaviour was characterized by an accurate determination of the pressure-volume equation of state, with a bulk modulus of 339(3) GPa and its derivative of 5.3(1). X-ray absorption spectroscopy, which probes the local structure and the empty density of electronic states above the Fermi level, was also utilized. The remarkable agreement observed between experimental and calculated spectra validates the reliability of theoretical predictions of the pressure dependence of the electronic structure of iridium in the studied interval of compressions.

Measuring the atomic scattering factors near the iridium L-edges for the Athena silicon pore optics reflector

“…The best values are listed in Table 6. The best fit parameters of the L3 edge were consistent with those by Monteseguro et al 25 The center energy of the arctan model representing a step-like edge feature is consistent with the L3 and L2 edge energies, although the best fitted center energy for iridium L1 edge is ∼8 eV greater than the iridium L1 edge energy.…”

“…To characterize the L-edge structures, we fitted the f 2 obtained from the fine pitch scans with a Lorentzian + arctan model in which a Lorentzian represents a sharp line and an arctan represents a step-like edge feature. 25 The L-edge structures were well represented by this model as seen in Fig. 14.…”

Unveiling the Ir single atoms as selective active species for the partial hydrogenation of butadiene by operando XAS

“…3A, the Ir L 3 -edge XANES spectra are characterized by a white line, which corresponds to transitions from the occupied 2p 3/2 core electron level to empty 5d states, thus probing the local density of unoccupied final states in the system. 43 It is obvious from Fig. 3 that the white line of the Ir-SAC is comparable to that of IrO 2 and more intense than that of the Ir-NC.…”

Crystal-field mediated electronic transitions of EuS up to 35 GPa

“…Pressure was determined through the luminescence of a ruby placed inside the cell chamber. The XANES profiles were fitted by the sum of an arctangent and a Lorentz function 33 in order to obtain the integrated intensities and the energy position of WL associated to the and the edges as a function of pressure. The modification of the pressure-induced Eu valence state was derived by fitting the relative changes of the spectral weights ( and ) of the Eu ( ) and Eu ( ) contribution of the XANES.…”