Quadrupole interactions in tetraoxoferrates (VI)
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Quadrupole interactions in tetraoxoferrates (VI) Sergey K. Dedushenko · Yurii D. Perfiliev · Vyacheslav S. Rusakov · Alexei M. Gapochka
Published online: 10 April 2013 © Springer Science+Business Media Dordrecht 2013
Abstract An applicability of the point charge approach for calculations of quadrupole splittings in Mössbauer spectra of ferrates(VI) was studied. The reasonable correlation between calculated and experimental splittings was observed for the majority of ferrates excepting K3 Na(FeO4 )2 . The comparison of ferrates and chromates was made using calculated nucleus independent coefficient. Keywords Mössbauer spectroscopy · Hexavalent iron · Tetraoxoferrate(VI) · Ferrate · Chromate · EFG calculation · Quadrupole splitting · Point-charge model
1 Introduction There is a growing interest in the ferrate technology of water treatment [1, 2]. This technology consists of introduction of tetraoxoferrate(VI)-anion (ferrate-ion, FeO2− 4 ) into contaminated water for the purpose of oxidation of toxic substances and/or co-precipitation of these substances and/or the products of their reduction with colloidal precipitate of iron(III) oxohydroxoderivatives, which are formed during reduction of the ferrate-ions: − 2 FeO2− 4 + 5 H2 O → 4 OH + 2 Fe (OH)3 ↓ +3 O
Proceedings of the 4th Joint International Conference on Hyperfine Interactions and International Symposium on Nuclear Quadrupole Interactions (HFI/NQI 2012), Beijing, China, 10–14 September 2012. S. K. Dedushenko (B) · Y. D. Perfiliev Department of Chemistry, Moscow State University, Moscow, Russia e-mail: [email protected] V. S. Rusakov · A. M. Gapochka Department of Physics, Moscow State University, Moscow, Russia
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Ferrate-ion is the only known Fe6+ -containing ion, which existence is reliably confirmed. In combinations with several metallic cations this anion gives the salts— ferrates. Regardless of salt compositions ferrate-ion is the almost regular tetrahedron consisting of four O2− -ions with Fe6+ -ion in the center. Quadrupole splitting in Mössbauer spectra of ferrates has not been observed for a long time. But recently quadrupole splittings in Mössbauer spectra have been reliably detected for two compounds: BaFeO4 and K3 Na(FeO4 )2 . These salts show two resolved doublet lines in their spectra [3, 4]. Ferrates are ionic compounds; iron has two unpaired electrons on its valent shell (3d2 -configuration). The application of simple theoretical models for the explanation of optical, magnetic or other properties of such compounds and ions commonly gives acceptable results [5]. In this work we studied an applicability of the point charge approach for calculations of ferrate quadrupole splittings. This approach presumes that quadrupole splitting is determined only by charges of ions composing a crystal lattice and by the arrangement of these ions around the observation point (e.g. around one of the Fe6+ -ions).1 The influence of an electron shell is not taken into account.
2 Calculation To calculate splittings we used LATTICE pr
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