Oxidation state of uranium in A 6Cu 12U 2S 15 (A = K, Rb, Cs) compounds

Christos D. Malliakas, Jiyong Yao, Daniel M. Wells, Geng Bang Jin, S. Skanthakumar, Eun Sang Choi, Mahalingam Balasubramanian, L. Soderholm, Donald E. Ellis, Mercouri G Kanatzidis, James A. Ibers

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Abstract

Black single crystals of A 6Cu 12U 2S 15 (A = K, Rb, Cs) have been synthesized by the reactive flux method. These isostructural compounds crystallize in the cubic space group Ia3̄d at room temperature. The structure comprises a three-dimensional framework built from US 6 octahedra and CuS 3 trigonal planar units with A cations residing in the cavities. There are no S-S bonds in the structure. To elucidate the oxidation state of U in these compounds, various physical property measurements and characterization methods were carried out. Temperature-dependent electrical resistivity measurement on a single crystal of K 6Cu 12U 2S 15 showed it to be a semiconductor. These three A 6Cu 12U 2S 15 (A = K, Rb, Cs) compounds all exhibit small effective magnetic moments, <0.58 μ B/U and band gaps of about 0.55(2) eV in their optical absorption spectra. From X-ray absorption near edge spectroscopy (XANES), the absorption edge of A 6Cu 12U 2S 15 is very close to that of UO 3. Electronic band structure calculations at the density functional theory (DFT) level indicate a strong degree of covalency between U and S atoms, but theory was not conclusive about the formal oxidation state of U. All experimental data suggest that the A 6Cu 12U 2S 15 family is best described as an intermediate U 5+/U 6+ sulfide system of (A +) 6(Cu +) 12(U 5+) 2(S 2-) 13(S -) 2 and (A +) 6(Cu +) 12(U 6+) 2(S 2-) 15.

Original languageEnglish
Pages (from-to)6153-6163
Number of pages11
JournalInorganic Chemistry
Volume51
Issue number11
DOIs
Publication statusPublished - Jun 4 2012

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Uranium
uranium
Single crystals
Oxidation
oxidation
single crystals
X ray absorption
Sulfides
Magnetic moments
Band structure
Light absorption
Density functional theory
Cations
optical spectrum
sulfides
Absorption spectra
Energy gap
optical absorption
Physical properties
physical properties

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Physical and Theoretical Chemistry

Cite this

Malliakas, C. D., Yao, J., Wells, D. M., Jin, G. B., Skanthakumar, S., Choi, E. S., ... Ibers, J. A. (2012). Oxidation state of uranium in A 6Cu 12U 2S 15 (A = K, Rb, Cs) compounds. Inorganic Chemistry, 51(11), 6153-6163. https://doi.org/10.1021/ic300172k

Oxidation state of uranium in A 6Cu 12U 2S 15 (A = K, Rb, Cs) compounds. / Malliakas, Christos D.; Yao, Jiyong; Wells, Daniel M.; Jin, Geng Bang; Skanthakumar, S.; Choi, Eun Sang; Balasubramanian, Mahalingam; Soderholm, L.; Ellis, Donald E.; Kanatzidis, Mercouri G; Ibers, James A.

In: Inorganic Chemistry, Vol. 51, No. 11, 04.06.2012, p. 6153-6163.

Research output: Contribution to journalArticle

Malliakas, CD, Yao, J, Wells, DM, Jin, GB, Skanthakumar, S, Choi, ES, Balasubramanian, M, Soderholm, L, Ellis, DE, Kanatzidis, MG & Ibers, JA 2012, 'Oxidation state of uranium in A 6Cu 12U 2S 15 (A = K, Rb, Cs) compounds', Inorganic Chemistry, vol. 51, no. 11, pp. 6153-6163. https://doi.org/10.1021/ic300172k
Malliakas CD, Yao J, Wells DM, Jin GB, Skanthakumar S, Choi ES et al. Oxidation state of uranium in A 6Cu 12U 2S 15 (A = K, Rb, Cs) compounds. Inorganic Chemistry. 2012 Jun 4;51(11):6153-6163. https://doi.org/10.1021/ic300172k
Malliakas, Christos D. ; Yao, Jiyong ; Wells, Daniel M. ; Jin, Geng Bang ; Skanthakumar, S. ; Choi, Eun Sang ; Balasubramanian, Mahalingam ; Soderholm, L. ; Ellis, Donald E. ; Kanatzidis, Mercouri G ; Ibers, James A. / Oxidation state of uranium in A 6Cu 12U 2S 15 (A = K, Rb, Cs) compounds. In: Inorganic Chemistry. 2012 ; Vol. 51, No. 11. pp. 6153-6163.
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AU - Yao, Jiyong

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AU - Jin, Geng Bang

AU - Skanthakumar, S.

AU - Choi, Eun Sang

AU - Balasubramanian, Mahalingam

AU - Soderholm, L.

AU - Ellis, Donald E.

AU - Kanatzidis, Mercouri G

AU - Ibers, James A.

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N2 - Black single crystals of A 6Cu 12U 2S 15 (A = K, Rb, Cs) have been synthesized by the reactive flux method. These isostructural compounds crystallize in the cubic space group Ia3̄d at room temperature. The structure comprises a three-dimensional framework built from US 6 octahedra and CuS 3 trigonal planar units with A cations residing in the cavities. There are no S-S bonds in the structure. To elucidate the oxidation state of U in these compounds, various physical property measurements and characterization methods were carried out. Temperature-dependent electrical resistivity measurement on a single crystal of K 6Cu 12U 2S 15 showed it to be a semiconductor. These three A 6Cu 12U 2S 15 (A = K, Rb, Cs) compounds all exhibit small effective magnetic moments, <0.58 μ B/U and band gaps of about 0.55(2) eV in their optical absorption spectra. From X-ray absorption near edge spectroscopy (XANES), the absorption edge of A 6Cu 12U 2S 15 is very close to that of UO 3. Electronic band structure calculations at the density functional theory (DFT) level indicate a strong degree of covalency between U and S atoms, but theory was not conclusive about the formal oxidation state of U. All experimental data suggest that the A 6Cu 12U 2S 15 family is best described as an intermediate U 5+/U 6+ sulfide system of (A +) 6(Cu +) 12(U 5+) 2(S 2-) 13(S -) 2 and (A +) 6(Cu +) 12(U 6+) 2(S 2-) 15.

AB - Black single crystals of A 6Cu 12U 2S 15 (A = K, Rb, Cs) have been synthesized by the reactive flux method. These isostructural compounds crystallize in the cubic space group Ia3̄d at room temperature. The structure comprises a three-dimensional framework built from US 6 octahedra and CuS 3 trigonal planar units with A cations residing in the cavities. There are no S-S bonds in the structure. To elucidate the oxidation state of U in these compounds, various physical property measurements and characterization methods were carried out. Temperature-dependent electrical resistivity measurement on a single crystal of K 6Cu 12U 2S 15 showed it to be a semiconductor. These three A 6Cu 12U 2S 15 (A = K, Rb, Cs) compounds all exhibit small effective magnetic moments, <0.58 μ B/U and band gaps of about 0.55(2) eV in their optical absorption spectra. From X-ray absorption near edge spectroscopy (XANES), the absorption edge of A 6Cu 12U 2S 15 is very close to that of UO 3. Electronic band structure calculations at the density functional theory (DFT) level indicate a strong degree of covalency between U and S atoms, but theory was not conclusive about the formal oxidation state of U. All experimental data suggest that the A 6Cu 12U 2S 15 family is best described as an intermediate U 5+/U 6+ sulfide system of (A +) 6(Cu +) 12(U 5+) 2(S 2-) 13(S -) 2 and (A +) 6(Cu +) 12(U 6+) 2(S 2-) 15.

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