Structure of UOSe

Black single crystals of Cs2U2(P2Se9)(Se2)2 were synthesized at 1023 K by a solid‐state reaction. Its structure was determined by single‐crystal X‐ray diffraction methods. The compound is isostructural with Rb2U2(P2Se9)(Se2)2 and Cs2Th2(P2Se9)(Se2)2 compounds, and crystallizes in the orthorhombic space group Pbca. Cs2U2(P2Se9)(Se2)2 displays a three‐dimensional structure comprising USe9 polyhedra connected via the Se22– and P2Se9 species with channels filled by Cs atoms. From electronic structure calculations the compound is found to be a metal with a ferromagnetic arrangement of the magnetic moments.

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“…The crystals appear to be stable in air for at least a month. UOSe and BaSe were also observed as impurities.…”

Section: Resultsmentioning

confidence: 98%

Synthesis and Crystal Structure of Cs₂U₂(P₂Se₉)(Se₂)₂

Mesbah

Prakash

Beard

et al. 2018

Zeitschrift anorg allge chemie

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“…In addition to BaUSe 3 (Ba:U:Se ≈ 1:1:3), the reaction product also contained reddish block-shaped crystals of BaSe 37 (Ba:Se ≈ 1:1), black blocks of Ba 4 USe 6 29 (Ba:U:Se ≈ 4:1:6), and black plates of UOSe. 38 Anaerobic Synthesis of BaUSe 3 . Because of the discrepancy between the experimental and theoretical band gaps (see below), the synthesis was repeated in a manner that avoided any possible air oxidation and light sensitivity of the product.…”

Section: ■ Experimental Methodsmentioning

confidence: 99%

Synthesis, Crystal Structure, Theoretical, and Resistivity Study of BaUSe₃

et al. 2016

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The black-colored compound BaUSe3 has been synthesized at 1173 K by a stoichiometric reaction of the elements in a CsCl flux. BaUSe3 crystallizes in the GdFeO3 structure type. There is no change in structure between 100 and 298 K. The U atoms in this structure are octahedrally connected to six Se atoms. Each octahedral unit shares all six corners with neighboring octahedra, forming a three-dimensional network. BaUSe3 can be charge balanced as Ba(2+)U(4+)(Se(2-))3. DFT electronic structure calculations found BaUSe3 to be antiferromagnetic in its ground state and to be a semiconductor with a band gap of 2.5 eV. The band gap is inconsistent with the black color of the material and with the small activation energy of 0.12(1) eV obtained from resistivity measurements. A UV-vis spectrum indicated that there was no band gap above 1 eV. It is possible that, for BaUSe3, intrinsic and extrinsic impurities from the flux create midgap states that lead to the experimentally measured narrow optical gap. More likely, BaUSe3 presents a challenge to DFT calculations as applied to 5f materials.

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“…In each instance from among those crystals one was selected for the X-ray structure determination. [26] and UOSe [25].…”

Section: Synthesesmentioning

confidence: 98%