Relativistic tight-binding calculation of core-valence transitions in Pt and Au

The results of a relativistic tight-binding energy-band model for Pt and Au, utilizing parameters derived from Smith's empirically adjusted combined interpolation scheme, are applied to calculate the one-electron contribution to various x-ray and energy-loss spectra involving 4f and 2p core states in these materials. These results show that the unoccupied holes in the Pt 5d bands have predominantly j=5/2 character (h_5/2) such that the (h_5/2/h_3/2) ratio ranges from ∼3.5 within 0.5 eV of E_F to ∼2.9 over the entire unoccupied conduction band. Taking into account dipole transition probabilities, the former ratio leads to a predicted line-strength ratio I_N7/I_N6≈2.9 near threshold for excitations involving the 4fj=7/2(N₇) and j=5/2(N₆) core levels in Pt. This result is in good agreement with the corresponding experimental ratios that are derived from electron energy-loss (2.5) and x-ray-absorption (2.3) spectra. Comparable agreement is obtained between the calculated and observed (electron-energy-loss) I_N7/I_N6 ratios in Au. The present results are applied to calculate the N₆-N₇ x-ray emission spectra in both Pt and Au and to interpret the L₂-L₃ absorption-edge data in Pt.