| Intermetallic compounds, containing metals or metalloids in definite ratios, are a broad class of materials with a wide range of properties, structures, and applications. X-ray photoelectron spectroscopy (XPS), photoemission spectroscopy (PES), and X-ray absorption near-edge spectroscopy (XANES) were used to investigate the electronic structure of several transition-metal pnictides (Pn = P, As, Sb).;Monophosphides, MP, having the MnP-type structure were examined by XPS. The charges were found to be closer to M 1+P1- than M3+P 3- and the P 2p XPS binding energies decrease linearly because the M-P bond becomes more ionic as M is changed from Co to Cr. In contrast, the mixed-metal phosphides M 1-xM'xP ( M is more electronegative than M') and mixed arsenide phosphides MAs1-yP y do not interpolate with the linear trend seen for MP, with the P 2p binding energies being lower than expected. These shifts were found by XANES to result from a next-nearest neighbour effect involving M'→M charge transfer in M1-xMxP and As→P charge transfer in MAs1- yPy, lowering the Madelung potential operating on the P site and thus the P 2p binding energy.;CoAs3-type (skutterudite) compounds of the form RE Fe4Pn12 (RE = La, Ce) and CoPn3 were also examined by XPS. Analysis of the spectra of the RE members led to the charge formulation RE3+ (Fe2)4(Pn 1-)12. The Ce charge was confirmed by the presence of a Ce 4f peak in the valence band spectrum. The Co 2p spectra of CoPn 3 showed no appreciable shift in energy relative to Co metal because of the delocalized valence electronic structure. However, the higher binding energy plasmon loss satellite peak observed in the Co 2p spectra was informative. In the series CoPn3, CoP, and Co metal, this satellite peak intensifies as the Co-Pn bond becomes more covalent and as the Co charge decreases.;A new metallic compound, Hf(Si0.5As0.5)As, having the ZrSiS-type structure was identified. The atomic charges are not as extreme as those predicted from an ionic model. Using XPS and PES, the charge formulation was revealed to be Hf2+[(Si0.5As 0.5)As]2-. These charges were determined by fitting the valence band spectrum, allowing for the number of valence electrons per atom to be extracted. |
