Paxton, A.T., van Schilfgaarde, M., MacKenzie, M., and Craven, A.J. (2000) The near-edge structure in energy-loss spectroscopy: many-electron and magnetic effects in transition metal nitrides and carbides. Journal of Physics: Condensed Matter, 12 (5). 729 -750. ISSN 0953-8984 (doi:10.1088/0953-8984/12/5/319)
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Publisher's URL: http://dx.doi.org/10.1088/0953-8984/12/5/319
We investigate the ability of the local density approximation (LDA) in density functional theory to predict the near-edge structure in electron energy loss spectroscopy in the dipole approximation. We include screening of the core hole within the LDA using Slater's transition state theory. We find that anion K-edge threshold energies are systematically overestimated by 4.22+or-0.44 eV in twelve transition metal carbides and nitrides in the rock salt (B1) structure. When we apply this `universal' many-electron correction to energy-loss spectra calculated within the transition state approximation to LDA, we find quantitative agreement with experiment to within one or two eV for TiC, TiN and VN. We compare our calculations to a simpler approach using a projected Mulliken density which honours the dipole selection rule, in place of the dipole matrix element itself. We find remarkably close agreement between these two approaches. Finally, we show an anomaly in the near-edge structure in CrN to be due to magnetic structure. In particular, we find that the N K edge in fact probes the magnetic moments and alignments of the the Cr sublattice.
|Glasgow Author(s):||MacKenzie, Dr Maureen and Craven, Prof Alan|
|Authors:||Paxton, A.T., van Schilfgaarde, M., MacKenzie, M., and Craven, A.J.|
|Subjects:||Q Science > QC Physics|
|College/School:||College of Science and Engineering > School of Physics and Astronomy|
|Journal Name:||Journal of Physics: Condensed Matter|