Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Garvie, L. A.J. Articles by Buseck, P. R. Search for Related Content GeoRef GeoRef Citation

Unoccupied states of pyrite probed by electron energy-loss spectroscopy (EELS)

¹ Department of Geological Sciences, Arizona State University, Tempe, Arizona 85287-1404, U.S.A.
² Department of Chemistry/Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, U.S.A.

Correspondence: ^* E-mail: lgarvie{at}asu.edu

Electron energy-loss spectra (EELS) of pyrite (FeS₂) were acquired and include the Fe K, L_2,3, M_2,3, and M₁ edges, and the S K, L_2,3, and L₁ edges. The core-loss edges exhibit a range of shapes and different theories are required to understand the spectra. In the process a clear picture of the conduction-band states as a function of energy above the band gap is obtained. This analysis reveals the extent of mixing of unoccupied states and thus provides an understanding of the limits of interpreting core-loss edges in light of the optical dipole limit. A unified picture of the unoccupied states is obtained by aligning the spectra on a common energy scale relative to the published Bremsstrahlung isochromat spectrum (BIS) and with the results of band structure calculations. This alignment allows similarities between the spectra of different atoms to be related to mixing of local conduction-band states. The coincidence of the Fe K and S L_2,3 spectral features attests to the strong hybridization of the Fe p-S 3d states. The main Fe L_2,3 edges are followed by structures that confirm an Fe-S bond with a substantial degree of mixing between Fe d⁶ and d⁷ states. The aligned EELS spectra clearly divide the unoccupied states into two regions. The first region is dominated by the intense d-like component of the Fe L₃ edge and p-like components of the S K and L₁ edges. A small pre-peak at the Fe K edge aligned with the Fe L_2,3 edge peak maximum is indicative of Fe 4p + 3d e_g and S 3p mixing. Similarly, the pre-peak to the S L_2,3 edge arises from transitions to states with mixed S s + p + Fe 3d e_g character.