K- and L-edge X-ray absorption spectrum calculations of closed-shell carbon, silicon, germanium, and sulfur compounds using damped four-component density functional response theory
2016 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 19, 13591-13603 p.Article in journal (Other academic) Published
X-ray absorption spectra of carbon, silicon, germanium, and sulfur compounds have been investigated by means of damped four-component density functional response theory. It is demonstrated that a reliable description of relativistic effects is obtained at both K- and L-edges. Notably, an excellent agreement with experimental results is obtained for L2,3-spectra—with spin-orbit effects well accounted for—also in cases when the experimental intensity ratio deviate from the statistical one of 1:2. The theoretical results are consistent with calculations using standard response theory as well as recently reported real-time propagation methods in time-dependent density functional theory, and the virtues of different approaches are discussed. As compared to silane and silicon tetrachloride, an anomalous error in the absolute energy is reported for the L2,3-spectrum of silicon tetrafluoride, amounting to an additional spectral shift of ~ 1 eV. This anomaly is observed also for other exchange-correlation functionals, but it is seen neither at other silicon edges nor at the carbon K-edge of fluorine derivatives of ethene. Considering the series of molecules SiH4−XFX with X = 1, 2, 3, 4, a gradual divergence from interpolated experimental ionization potentials is observed at the level of Kohn–Sham density functional theory (DFT), and to a smaller extent with use of Hartree–Fock. This anomalous error is thus attributed partly to difficulties in correctly emulating the electronic structure effects imposed by the very electronegative fluorines, and partly due to inconsistencies in the spurious electron self-repulsion in DFT. Substitution with one, or possibly two, fluorine atoms is estimated to yield small enough errors to allow for reliable interpretations and predictions of L2,3-spectra of more complex and extended silicon-based systems.
Place, publisher, year, edition, pages
Royal Society of Chemistry, 2016. Vol. 18, no 19, 13591-13603 p.
IdentifiersURN: urn:nbn:se:liu:diva-124271DOI: 10.1039/c6cp00561fISI: 000376138000050OAI: oai:DiVA.org:liu-124271DiVA: diva2:897210
Funding agencies. Knut and Alice Wallenberg Foundation [KAW-2013.0020]; Swedish Research Council [621-2014-4646]2016-01-252016-01-252016-06-13Bibliographically approved