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

doi:10.1021/ic300172k

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

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

24 Scopus citations

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 language	English (US)
Pages (from-to)	6153-6163
Number of pages	11
Journal	Inorganic chemistry
Volume	51
Issue number	11
DOIs	https://doi.org/10.1021/ic300172k
State	Published - Jun 4 2012

ASJC Scopus subject areas

Physical and Theoretical Chemistry
Inorganic Chemistry

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10.1021/ic300172k

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@article{a5309f9c3c1644278b3f1547e1c9797e,

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

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 Ia{\=3}d 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.",

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

year = "2012",

month = jun,

day = "4",

doi = "10.1021/ic300172k",

language = "English (US)",

volume = "51",

pages = "6153--6163",

journal = "Inorganic Chemistry",

issn = "0020-1669",

publisher = "American Chemical Society",

number = "11",

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TY - JOUR

T1 - Oxidation state of uranium in A 6Cu 12U 2S 15 (A = K, Rb, Cs) compounds

AU - Malliakas, Christos D.

AU - Yao, Jiyong

AU - Wells, Daniel M.

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.

PY - 2012/6/4

Y1 - 2012/6/4

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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DO - 10.1021/ic300172k

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JO - Inorganic Chemistry

JF - Inorganic Chemistry

SN - 0020-1669

IS - 11

ER -

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

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