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

Abstract

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», ) such that the (h5/2/A3/2) ratio ranges from -3.5 within 0.5 eV of EF 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",/I", -2.9 near threshold for excitations involving the 4fj = 7/2 (N,) and j = 5/2 {N,) 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)

Strong Support Effects on the Insulator to Metal Transition in Supported Pt Clusters as Observed by X-ray Absorption Spectroscopy

“…The much smaller whiteline intensity near the edge in the L 2 data compared to the L 3 in transition metal samples is well-known and arises from spin-orbit interactions in the Pt 5d state and the preferred selection rules as illustrated in the insert of Figure 2. 12 The 5d 5/2 -5d 3/2 spin-orbital splitting is ∼1.5-2.5 eV in Pt, and the results reported here indicate this splitting depends on even the particle support. The L 3 edge reflects the empty levels of both the d 5/2 and d 3/2 bands weighted as d 5/2 /d 3/2 ≈ 6; 12 however, the L 2 edge reflects only the d 3/2 level.…”

The metal–support interaction in Pt/Y zeolite: evidence for a shift in energy of metal d-valence orbitals by Pt–H shape resonance and atomic XAFS spectroscopy

“…1 [22]. The spin-orbit interaction in both core and valence levels introduces differences between the L 3 (2p 3/2 → 5d 5/2 , 5d 3/2 ) and L 2 (2p 1/2 → 5d 3/2 ) edges, both in shape and intensity (the 2p 3/2 -2p 1/2 splitting is around 1709 eV, and the 5d 5/2 -5d 3/2 splitting around is 1.5-2.5 eV [26]). The L 3 edge reflects the empty valence levels ( VB) of both d 5/2 and d 3/2 bands, weighted as d 5/2 /d 3/2 = 6 [26]; however, the L 2 edge reflects only the d 3/2 level.…”

Characterization of nickel silicides using EELS‐based methods

“…5(c), it is shown that by combining the white line intensity measurements with the branching ratio measurements, all the Ni-silicide phases except NiSi and NiSi 2 can be distinguished. Mattheiss & Dietz (1980) and Pearson et al (1993) reported that the total white line intensity is proportional to the number of valence d holes. They also showed that in order to extract quantitatively the number of 3d electrons, the radial matrix elements for the excitations of the 2p 3/2 and 2p 1/2 core (Massalski, 1990).…”

“…Pearson et al (1993) and Mattheiss & Dietz (1980) report a procedure by which EELS can provide information about the local occupation of 3d states in transition metals. They show that the sum of the intensities of the white lines (with the excitations to continuum removed) can be related to the occupancies of the corresponding outer d states.…”