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The X-ray emission spectra ( M ~-K B , , ~, Mg-LZ.3 M, and 0-K,), X-ray photoelectron spectra, and 0-KLL Auger spectra from brucite, Mg[OH],, are reported. The electronic structure of brucite is discussed using these spectra and a simple Huckel molecular-orbital model. The spectra indicate that the strongest interaction exists between the oxygen and hydrogen of the hydroxide group, but that the Mg-0 bond has some covalent character. An attempt to interpret the 2 ~-~ peak in the oxygen Auger spectrum using the 0 -K , X-ray profile has met with only I im i ted success. Chemistry, Queen Mary College, Mile End Road, London El 4NS * Throughout this paper: 1 eV E 1.60 x lO-lS J ; 1 Torr = (101 325/760) Pa.

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Iron(n) and (m) fluorides have been studied using X-ray emission (XE) and photoelectron (XP)spectroscopies. XE data enable the XP peaks to be identified unequivocally ; in the iron(m) compound the F 2p and Fe 3d orbitals were shown to have almost identical energy. The F Ka XE peak profile showed the Fe-F band to be more covalent in ferric than ferrous fluoride. Whilst the F Is binding energy was the same for both compounds a peak shift of 3.0-3.5 eV to higher binding energies was found for all iron orbitals upon oxidation. The rapid reduction of iron(m) to iron@) by argonion bombardment was observed.

The x-ray emission spectra (SKβ, SL, CuKβ, CuL, FeKβ, FeL) and x-ray photoelectron spectra of CuFeS2 chalcopyrite are reported and are interpreted using SCF-Xα MO calculations on the polyhedral anions CuS−74 and FeS−54 and discrete variational Xα band structure calculations. The highest energy occupied orbitals are found to be of Cu3d-S3p antibonding character. Substantial Fe3d character is observed across a broad range of binding energies indicating strong mixing of the Fe3d orbitals with both the Cu3d and S3p. Both the Xα cluster calculation on FeS−54 and the Xα band structure calculations overestimate the Fe3d orbital binding energies, although the discrepancy is smaller in the band calculation. Both computational methods predict the lowest energy empty orbitals to be of Fe3d-S3p antibonding character with a small (<2 eV) separation from the highest occupied orbitals. This small energy difference provides a possible explanation for the metallic conductivity observed in CuFeS2 at high pressure, particularly if the CuT–S bond is more compressible than the Feiii–S as is expected from compressibility-formal charge systematics.