Photoemission spectra and band structures ofd-band metals. IV. X-ray photoemission spectra and densities of states in Rh, Pd, Ag, Ir, Pt, and Au

Abstract

X-ray photoemission spectroscopy (XPS) data for the valence bands of Rh, Pd, Ag, Ir, Pt, and Au are compared with densities of states calculated from interpolated band structures. The parameters of the interpolation scheme were obtained in an earlier paper by fitting first-principles augmented-plane-wave calculations, and then making adjustments, where necessary, to the width of the $d$ bands in order to improve agreement with ultraviolet photoemission spectroscopy (UPS) data. In the $4d$ metals, Rh, Pd, and Ag, there is excellent agreement between the energy positions of peaks in the occupied density of states and the XPS valence bands. In the $5d$ metals, Ir, Pt, and Au, the agreement is reasonable, but inferior to that for the $4d$ metals particularly in the middle of the $d$-band region. It is argued that the main discrepancies in peak locations are not significant and are most likely due to the approximations in the interpolated band structures, particularly those involved in the spin-orbit splitting and hybridization. The relative intensity of the XPS data in the lower-energy region of the $d$ bands is consistently lower than that in the density of states, indicating appreciable modulation of the spectra by optical-transition strengths.