Refinement of the crystal structure of UOs2 from single-crystal X-ray diffraction data

Ivlev, S.I.; Conrad, M.; Wolf, C.; Kraus, F.

doi:10.1107/S2414314626006917

inorganic compounds

IUCrDATA

ISSN: 2414-3146

Volume 11| Part 7| July 2026| x260691

https://doi.org/10.1107/S2414314626006917

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Refinement of the crystal structure of UOs₂ from single-crystal X-ray diffraction data

Sergei I. Ivlev,^a Matthias Conrad,^a Carsten Wolf ^b and Florian Kraus ^c ^*

^aPhilipps-Universität Marburg, Fachbereich Chemie, Hans-Meerwein-Str. 4, 35032 Marburg, Germany, ^bBruker AXS SE, Östliche Rheinbrückenstrasse 49, 76187 Karlsruhe, Germany, and ^cAnorganische Chemie, Fluorchemie, Institut für Anorganische Chemie, Universität Bonn, Gerhard-Domagk-Strasse 1, 53121 Bonn, Germany
^*Correspondence e-mail: [email protected]

Edited by M. Weil, Vienna University of Technology, Austria (Received 9 June 2026; accepted 2 July 2026; online 7 July 2026)

Single crystals of uranium diosmium, UOs₂, were obtained during an investigation of the uranium-osmium binary system by an interaction of uranium metal with osmium metal in an arc furnace and subsequent annealing. The refinement of the crystal structure of UO₂ was carried out for the first time using single-crystal X-ray diffraction data. In contrast to previous structure reports based on powder diffraction data, the U and Os atoms were refined with all U^ij terms of the displacement parameters considered. UOs₂ adopts the MgCu₂ structure type.

Keywords: crystal structure; intermetallics; single-crystal X-ray diffraction; redetermination; MgCu₂ structure type.

CCDC reference: 2567529

Structure description

According to the Inorganic Crystal Structure Database (ICSD; Zagorac et al., 2019 ), the first crystal structure determination of the binary phase UOs₂ was carried out by Heal & Williams (1955 ) using a powder sample and a diffractometer operated with Co radiation. They reported the compound to crystallize in the space group Fd $[\overline{3}]$ m (No. 227) with a = 7.5125 (5) Å, V = 423.99 Å³, Z = 8 at 297 K belonging to the MgCu₂ structure type. Subsequent structure reports confirmed this finding with the unit-cell parameter to be in very close agreement with the one originally reported: 7.514 Å [Knapton, 1963 ; room-temperature data, no standard uncertainty (s.u.) given]; 7.501 (4) Å (Holleck et al., 1975 ; room-temperature data); 7.514 Å (Mentink et al., 1992 ; room-temperature data, no s.u. given); 7.4919 (Nishioka et al., 1994 ; room-temperature data, no s.u. given). Nishioka et al. (1994) also reported the existence of a polymorph of UOs₂ belonging to the MgZn₂ structure type [space group P6₃/mmc (No. 194) with a = 5.49, c = 8.71 Å, V = 227.35 Å³, Z = 4; room temperature data, no s.u. given]. All mentioned crystal-structure refinements were carried out on the basis of powder diffraction techniques with both Os and U atoms being refined isotropically. Although an anisotropic refinement of the U atom is equivalent to the isotropic one due to symmetry constraints, the site symmetry of the Os atom does allow non-zero off-diagonal U^ij terms, when refined anisotropically. Here we report our results on the crystal-structure determination of UOs₂ using single-crystal X-ray diffraction data at 100 K that allowed to use the anisotropic approximation for the displacement parameters (Fig. 1).

Figure 1
Crystal structure of UOs₂ in a projection along [100]. Displacement ellipsoids are shown at the 90% probability level.

The unit-cell parameter of UOs₂ obtained from the single-crystal diffraction experiment (Table 1) is in good agreement with all previously reported data. The U atom resides on the special 8a ( $[\overline{4}]$ 3m) Wyckoff position. The Os atom occupies the special 16d (. $[\overline{3}]$ m) Wyckoff position. The closest interatomic distances are U⋯U 3.24669 (8), Os⋯Os 2.65091 (7), and U⋯Os 3.10847 (8) Å.

Table 1
Experimental details

Crystal data
Chemical formula	UOs₂
M_r	618.43
Crystal system, space group	Cubic, Fd $[\overline{3}]$ m
Temperature (K)	100
a (Å)	7.4979 (2)
V (Å³)	421.52 (3)
Z	8
Radiation type	Mo Kα
μ (mm⁻¹)	196.43
Crystal size (mm)	0.05 × 0.04 × 0.03

Data collection
Diffractometer	Bruker D8 VENTURE
Absorption correction	Numerical (SADABS; Krause et al., 2015 )
T_min, T_max	0.014, 0.127
No. of measured, independent and observed [I > 2σ(I)] reflections	2221, 69, 66
R_int	0.083
(sin θ/λ)_max (Å⁻¹)	0.830

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.020, 0.047, 1.40
No. of reflections	69
No. of parameters	5
Δρ_max, Δρ_min (e Å⁻³)	1.92, −2.16
Computer programs: APEX5 (Bruker, 2023 ), SAINT (Bruker, 2019 ), SHELXT (Sheldrick, 2015a ), SHELXL (Sheldrick, 2015b ), DIAMOND (Brandenburg, 2022 ) and publCIF (Westrip, 2010 ).

Since UOs₂ is isotypic to the well known Laves phase MgCu₂, its crystal structure will only be described very briefly. The U atoms are arranged like the atoms in the cubic diamond structure type. The Os atoms form Os₄ tetrahedra. Their virtual centres of gravity are also arranged according to the cubic diamond structure type, and the two networks interpenetrate. Overall, the coordination number of the Os atom is 12 within a slightly distorted icosahedral coordination environment. Each Os atom resides within the centre of a U₆ ring adopting a chair conformation and is additionally surrounded by six Os atoms in the shape of a trigonal antiprism. Overall, the coordination number of the U atom is 16. Each U atom is surrounded tetrahedrally by four U atoms and by twelve Os atoms in the shape of a fourfold truncated tetrahedron, which is sometimes referred to as the Friauf polyhedron (Wells, 1975 ).

Synthesis and crystallization

Single crystals of UOs₂ were obtained by a direct reaction between stoichiometric amounts of uranium and osmium metal powders in an arc furnace. The polycrystalline reaction product was subsequently annealed in a tantalum ampule at 1073 K for 11 d and crushed in oil under a microscope to select a single crystal suitable for the diffraction study.

Refinement

Details of data collection and structure refinement are given in Table 1.

Structural data

CCDC reference: 2567529

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314626006917/wm4251sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314626006917/wm4251Isup2.hkl

checkCIF report

Computing details top

Uranium diosmium top

Crystal data top

UOs₂	Mo Kα radiation, λ = 0.71073 Å
M_r = 618.43	Cell parameters from 2037 reflections
Cubic, Fd3m	θ = 4.7–36.2°
a = 7.4979 (2) Å	µ = 196.43 mm⁻¹
V = 421.52 (3) Å³	T = 100 K
Z = 8	Block, metallic grey
F(000) = 1952	0.05 × 0.04 × 0.03 mm
D_x = 19.490 Mg m⁻³

Data collection top

Bruker D8 VENTURE diffractometer	66 reflections with I > 2σ(I)
Radiation source: microfocus X-ray tube	R_int = 0.083
ω and φ scans	θ_max = 36.2°, θ_min = 4.7°
Absorption correction: numerical (SADABS; Krause et al., 2015)	h = −11→10
T_min = 0.014, T_max = 0.127	k = −10→11
2221 measured reflections	l = −12→10
69 independent reflections

Refinement top

Refinement on F²	Primary atom site location: dual
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.020	w = 1/[σ²(F_o²) + (0.0161P)² + 10.8153P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.047	(Δ/σ)_max < 0.001
S = 1.40	Δρ_max = 1.92 e Å⁻³
69 reflections	Δρ_min = −2.16 e Å⁻³
5 parameters	Extinction correction: SHELXL2019/2 (Sheldrick 2015b), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.00055 (10)

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
U1	0.875000	0.375000	0.375000	0.0088 (3)
Os1	0.500000	0.250000	0.250000	0.0082 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
U1	0.0088 (3)	0.0088 (3)	0.0088 (3)	0.000	0.000	0.000
Os1	0.0082 (3)	0.0082 (3)	0.0082 (3)	0.00062 (12)	0.00062 (12)	−0.00062 (12)

Geometric parameters (Å, º) top

U1—Os1ⁱ	3.1085 (1)	U1—Os1^xi	3.1085 (1)
U1—Os1	3.1085 (1)	U1—U1^xii	3.2467 (1)
U1—Os1ⁱⁱ	3.1085 (1)	U1—U1^xiii	3.2467 (1)
U1—Os1ⁱⁱⁱ	3.1085 (1)	U1—U1^xiv	3.2467 (1)
U1—Os1^iv	3.1085 (1)	U1—U1^xv	3.2467 (1)
U1—Os1^v	3.1085 (1)	Os1—Os1^xvi	2.6509 (1)
U1—Os1^vi	3.1085 (1)	Os1—Os1^ix	2.6509 (1)
U1—Os1^vii	3.1085 (1)	Os1—Os1^xvii	2.6509 (1)
U1—Os1^viii	3.1085 (1)	Os1—Os1ⁱ	2.6509 (1)
U1—Os1^ix	3.1085 (1)	Os1—Os1ⁱⁱ	2.6509 (1)
U1—Os1^x	3.1085 (1)	Os1—Os1^xviii	2.6509 (1)

Os1ⁱ—U1—Os1	50.5	Os1ⁱⁱ—U1—U1^xiv	58.5
Os1ⁱ—U1—Os1ⁱⁱ	50.5	Os1ⁱⁱⁱ—U1—U1^xiv	150.5
Os1—U1—Os1ⁱⁱ	50.5	Os1^iv—U1—U1^xiv	58.518 (1)
Os1ⁱ—U1—Os1ⁱⁱⁱ	144.9	Os1^v—U1—U1^xiv	100.025 (1)
Os1—U1—Os1ⁱⁱⁱ	95.2	Os1^vi—U1—U1^xiv	100.025 (1)
Os1ⁱⁱ—U1—Os1ⁱⁱⁱ	117.0	Os1^vii—U1—U1^xiv	58.518 (1)
Os1ⁱ—U1—Os1^iv	95.2	Os1^viii—U1—U1^xiv	150.5
Os1—U1—Os1^iv	144.9	Os1^ix—U1—U1^xiv	150.5
Os1ⁱⁱ—U1—Os1^iv	117.0	Os1^x—U1—U1^xiv	58.5
Os1ⁱⁱⁱ—U1—Os1^iv	117.0	Os1^xi—U1—U1^xiv	58.5
Os1ⁱ—U1—Os1^v	95.2	U1^xii—U1—U1^xiv	109.471 (1)
Os1—U1—Os1^v	117.0	U1^xiii—U1—U1^xiv	109.5
Os1ⁱⁱ—U1—Os1^v	144.9	Os1ⁱ—U1—U1^xv	58.5
Os1ⁱⁱⁱ—U1—Os1^v	95.2	Os1—U1—U1^xv	58.5
Os1^iv—U1—Os1^v	50.5	Os1ⁱⁱ—U1—U1^xv	100.0
Os1ⁱ—U1—Os1^vi	144.9	Os1ⁱⁱⁱ—U1—U1^xv	100.0
Os1—U1—Os1^vi	117.0	Os1^iv—U1—U1^xv	100.025 (1)
Os1ⁱⁱ—U1—Os1^vi	95.2	Os1^v—U1—U1^xv	58.5
Os1ⁱⁱⁱ—U1—Os1^vi	50.5	Os1^vi—U1—U1^xv	150.5
Os1^iv—U1—Os1^vi	95.2	Os1^vii—U1—U1^xv	150.5
Os1^v—U1—Os1^vi	117.0	Os1^viii—U1—U1^xv	58.5
Os1ⁱ—U1—Os1^vii	117.0	Os1^ix—U1—U1^xv	58.5
Os1—U1—Os1^vii	144.9	Os1^x—U1—U1^xv	150.5
Os1ⁱⁱ—U1—Os1^vii	95.2	Os1^xi—U1—U1^xv	58.5
Os1ⁱⁱⁱ—U1—Os1^vii	95.2	U1^xii—U1—U1^xv	109.471 (1)
Os1^iv—U1—Os1^vii	50.5	U1^xiii—U1—U1^xv	109.5
Os1^v—U1—Os1^vii	95.2	U1^xiv—U1—U1^xv	109.5
Os1^vi—U1—Os1^vii	50.5	Os1^xvi—Os1—Os1^ix	180.0
Os1ⁱ—U1—Os1^viii	117.0	Os1^xvi—Os1—Os1^xvii	120.0
Os1—U1—Os1^viii	95.2	Os1^ix—Os1—Os1^xvii	60.0
Os1ⁱⁱ—U1—Os1^viii	144.9	Os1^xvi—Os1—Os1ⁱ	60.0
Os1ⁱⁱⁱ—U1—Os1^viii	50.5	Os1^ix—Os1—Os1ⁱ	120.0
Os1^iv—U1—Os1^viii	95.2	Os1^xvii—Os1—Os1ⁱ	180.0
Os1^v—U1—Os1^viii	50.5	Os1^xvi—Os1—Os1ⁱⁱ	60.0
Os1^vi—U1—Os1^viii	95.2	Os1^ix—Os1—Os1ⁱⁱ	120.0
Os1^vii—U1—Os1^viii	117.0	Os1^xvii—Os1—Os1ⁱⁱ	120.0
Os1ⁱ—U1—Os1^ix	95.2	Os1ⁱ—Os1—Os1ⁱⁱ	60.0
Os1—U1—Os1^ix	50.5	Os1^xvi—Os1—Os1^xviii	120.0
Os1ⁱⁱ—U1—Os1^ix	95.2	Os1^ix—Os1—Os1^xviii	60.0
Os1ⁱⁱⁱ—U1—Os1^ix	50.5	Os1^xvii—Os1—Os1^xviii	60.0
Os1^iv—U1—Os1^ix	144.9	Os1ⁱ—Os1—Os1^xviii	120.0
Os1^v—U1—Os1^ix	95.2	Os1ⁱⁱ—Os1—Os1^xviii	180.0
Os1^vi—U1—Os1^ix	95.2	Os1^xvi—Os1—U1	115.2
Os1^vii—U1—Os1^ix	144.9	Os1^ix—Os1—U1	64.8
Os1^viii—U1—Os1^ix	50.5	Os1^xvii—Os1—U1	115.2
Os1ⁱ—U1—Os1^x	95.216 (1)	Os1ⁱ—Os1—U1	64.8
Os1—U1—Os1^x	95.2	Os1ⁱⁱ—Os1—U1	64.8
Os1ⁱⁱ—U1—Os1^x	50.5	Os1^xviii—Os1—U1	115.2
Os1ⁱⁱⁱ—U1—Os1^x	95.2	Os1^xvi—Os1—U1^xix	64.8
Os1^iv—U1—Os1^x	95.2	Os1^ix—Os1—U1^xix	115.2
Os1^v—U1—Os1^x	144.9	Os1^xvii—Os1—U1^xix	64.8
Os1^vi—U1—Os1^x	50.5	Os1ⁱ—Os1—U1^xix	115.2
Os1^vii—U1—Os1^x	50.5	Os1ⁱⁱ—Os1—U1^xix	115.2
Os1^viii—U1—Os1^x	144.9	Os1^xviii—Os1—U1^xix	64.8
Os1^ix—U1—Os1^x	117.0	U1—Os1—U1^xix	180.0
Os1ⁱ—U1—Os1^xi	50.5	Os1^xvi—Os1—U1^xv	115.2
Os1—U1—Os1^xi	95.2	Os1^ix—Os1—U1^xv	64.8
Os1ⁱⁱ—U1—Os1^xi	95.216 (1)	Os1^xvii—Os1—U1^xv	115.2
Os1ⁱⁱⁱ—U1—Os1^xi	144.9	Os1ⁱ—Os1—U1^xv	64.8
Os1^iv—U1—Os1^xi	50.5	Os1ⁱⁱ—Os1—U1^xv	115.2
Os1^v—U1—Os1^xi	50.5	Os1^xviii—Os1—U1^xv	64.8
Os1^vi—U1—Os1^xi	144.9	U1—Os1—U1^xv	63.0
Os1^vii—U1—Os1^xi	95.2	U1^xix—Os1—U1^xv	117.0
Os1^viii—U1—Os1^xi	95.2	Os1^xvi—Os1—U1^xx	64.8
Os1^ix—U1—Os1^xi	117.0	Os1^ix—Os1—U1^xx	115.239 (1)
Os1^x—U1—Os1^xi	117.0	Os1^xvii—Os1—U1^xx	64.8
Os1ⁱ—U1—U1^xii	150.5	Os1ⁱ—Os1—U1^xx	115.2
Os1—U1—U1^xii	150.5	Os1ⁱⁱ—Os1—U1^xx	64.8
Os1ⁱⁱ—U1—U1^xii	150.5	Os1^xviii—Os1—U1^xx	115.2
Os1ⁱⁱⁱ—U1—U1^xii	58.5	U1—Os1—U1^xx	117.0
Os1^iv—U1—U1^xii	58.5	U1^xix—Os1—U1^xx	63.0
Os1^v—U1—U1^xii	58.5	U1^xv—Os1—U1^xx	180.0
Os1^vi—U1—U1^xii	58.5	Os1^xvi—Os1—U1^xxi	64.8
Os1^vii—U1—U1^xii	58.5	Os1^ix—Os1—U1^xxi	115.2
Os1^viii—U1—U1^xii	58.5	Os1^xvii—Os1—U1^xxi	115.2
Os1^ix—U1—U1^xii	100.025 (1)	Os1ⁱ—Os1—U1^xxi	64.8
Os1^x—U1—U1^xii	100.0	Os1ⁱⁱ—Os1—U1^xxi	115.2
Os1^xi—U1—U1^xii	100.0	Os1^xviii—Os1—U1^xxi	64.8
Os1ⁱ—U1—U1^xiii	100.0	U1—Os1—U1^xxi	117.0
Os1—U1—U1^xiii	58.518 (1)	U1^xix—Os1—U1^xxi	63.0
Os1ⁱⁱ—U1—U1^xiii	58.518 (1)	U1^xv—Os1—U1^xxi	63.0
Os1ⁱⁱⁱ—U1—U1^xiii	58.5	U1^xx—Os1—U1^xxi	117.0
Os1^iv—U1—U1^xiii	150.5	Os1^xvi—Os1—U1^xiii	115.2
Os1^v—U1—U1^xiii	150.5	Os1^ix—Os1—U1^xiii	64.8
Os1^vi—U1—U1^xiii	58.5	Os1^xvii—Os1—U1^xiii	64.8
Os1^vii—U1—U1^xiii	100.0	Os1ⁱ—Os1—U1^xiii	115.2
Os1^viii—U1—U1^xiii	100.0	Os1ⁱⁱ—Os1—U1^xiii	64.8
Os1^ix—U1—U1^xiii	58.5	Os1^xviii—Os1—U1^xiii	115.2
Os1^x—U1—U1^xiii	58.5	U1—Os1—U1^xiii	63.0
Os1^xi—U1—U1^xiii	150.5	U1^xix—Os1—U1^xiii	117.0
U1^xii—U1—U1^xiii	109.471 (1)	U1^xv—Os1—U1^xiii	117.0
Os1ⁱ—U1—U1^xiv	58.5	U1^xx—Os1—U1^xiii	63.0
Os1—U1—U1^xiv	100.0	U1^xxi—Os1—U1^xiii	180.0

Symmetry codes: (i) −x+5/4, y, −z+1/4; (ii) −x+5/4, −y+1/4, z; (iii) −x+5/4, −y+3/4, z+1/2; (iv) −x+7/4, −y+3/4, z; (v) x+1/2, y+1/2, z; (vi) x+1/2, y, z+1/2; (vii) −x+7/4, y, −z+3/4; (viii) −x+5/4, y+1/2, −z+3/4; (ix) x, −y+3/4, −z+3/4; (x) x+1/2, −y+1/4, −z+3/4; (xi) x+1/2, −y+3/4, −z+1/4; (xii) −x+2, −y+1, −z+1; (xiii) −y+1, x−3/4, z+1/4; (xiv) −x+2, −y+1/2, −z+1/2; (xv) −x+3/2, −y+1, −z+1/2; (xvi) x, −y+1/4, −z+1/4; (xvii) −x+3/4, y, −z+3/4; (xviii) −x+3/4, −y+3/4, z; (xix) −x+1, −y+1/2, −z+1/2; (xx) x−1/2, y−1/2, z; (xxi) x−1/2, y, z−1/2.

Acknowledgements

We thank the DFG for very generous funding over the years.

Funding information

Funding for this research was provided by: Deutsche Forschungsgemeinschaft.

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