Crystal structure of the ‘missing’ inter­metallic compound BaCu5

Avinash, K.; Andrews, J.

doi:10.1107/S2056989026008248

early career research

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ISSN: 2056-9890

Volume 82| Part 9| September 2026| Pages 1016-1018

https://doi.org/10.1107/S2056989026008248

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Crystal structure of the ‘missing’ intermetallic compound BaCu₅

Kiran Avinash ^a and Justin Andrews ^a ^*

^aDepartment of Chemistry, Purdue University, 560 Oval Dr., West Lafayette, IN 47907-2084, USA
^*Correspondence e-mail: [email protected]

Edited by W. T. A. Harrison, University of Aberdeen, United Kingdom (Received 9 July 2026; accepted 10 August 2026; online 14 August 2026)

This article is part of the collection Early Career Scientists in Structural Science.

The copper-rich intermetallic compounds CaCu₅ and SrCu₅ are isostructural but the isomorphous compound BaCu₅ (barium pentacopper) has not been reported. The absence of any compound with the composition of BaCu₅ in the Ba–Cu phase diagram has previously been attributed to much larger radius of Ba. The structure of BaCu₅, which crystallizes in an orthorhombic cell (space group Pnma) with the rare SrZn₅ structure type is now reported The structure is characterized by a zigzag arrangement of infinite Ba chains ensconced in a Cu matrix. The Ba atom and three Cu atoms lie on special positions with m site symmetry and one Cu atom lies on a general crystallographic position.

Keywords: crystal structure; intermetallic; electride; missing phase.

CCDC reference: 2579957

1. Chemical context

Compounds with the stoichiometry (AE/RE)(TM)₅ (AE/RE = alkaline earth metal or rare earth; TM = transition metal) most often crystallize in the CaCu₅ structure type (space group P6/mmm). Materials that adopt this structure are important as permanent magnets and have been investigated as hydrogen storage alloys (Hou et al., 2007 ; Xu et al., 2022 ; Zhou et al., 2023 ; Liang et al., 2001 ). While the CaCu₅ structure type (e.g., SrCu₅, YCu₅, Figure 1a) is most common, some (AE/RE)(TM)₅ compounds adopt the BaZn₅ structure type (space group Cmcm) (Fig. 1b). Conversely, UCu₅ adopts the AuBe₅ structure type (space group F $[\overline{4}]$ 3m; Nakamura et al., 1990 ) (Fig. 1c). Generally, the connectivity of the Cu metal–metal bonded cage is dictated by the size of the alkaline earth or rare-earth metal. A less-common structure type is the SrZn₅ structure (space group Pnma) (Fig. 1d), for which only four members have been reported (Simura & Yamane, 2019 ; Schwickert & Pöttgen, 2014 ; Bruzzone & Merlo, 1983 ). The Cu cage arrangements for each structure are shown in Fig. 1a–d.

Figure 1
(a) Reported structure of CaCu₅. (b) Reported structure of BaZn₅. (c) Reported structure of UCu₅. (d) Reported structure of SrZn₅. The corresponding arrangement and bonding of alkaline-earth metals in each structure is shown, and relevant bond distances are highlighted. Note that in the case of the structure of UCu₅, there is no U—U bonding.

For the (AE)Cu₅ series of materials, the eponymous CaCu₅ and the larger SrCu₅ compounds are known to adopt the same structure (Bruzzone, 1971 ; Boeije et al., 2017 ). However, a compound with the composition of BaCu₅ has never been reported. The original study that systematically explored the (Ca/Sr/Ba)—Cu phase diagram remarked on the conspicuous absence of a BaCu₅ compound and attributed its absence to the much larger size of Ba (Bruzzone, 1971).

Here we report on the structure of BaCu₅ and show that unlike CaCu₅, SrCu₅, and BaZn₅ (Bruzzone et al., 1985 ) it adopts the very rare SrZn₅ structure type (Bruzzone & Merlo, 1983).

2. Structural commentary

BaCu₅ crystallizes in the orthorhombic Pnma space group and adopts the rare SrZn₅ structure type, rather than the more common CaCu₅ structure type adopted by the lighter alkaline-earth analogues CaCu₅ and SrCu₅. The asymmetric unit contains one crystallographically independent Ba atom and four crystallographically independent Cu atoms. The Ba atom and three Cu atoms occupy special positions with site symmetry m, whereas one Cu atom occupies a general position. The structure consists of a three-dimensional Cu framework that forms one-dimensional tunnels extending parallel to the crystallographic a axis, within which infinite zigzag chains of Ba atoms are accommodated (Fig. 2).

Figure 2
Structure of BaCu₅. (a) projection of the structure along the crystallographic b-axis direction. (b) Ba occupies one-dimensional tunnels in the Cu framework. (c) View of one zigzag chain of Ba atoms propagating along the crystallographic a-axis direction.

The Ba atoms form planar zigzag chains with a nearest-neighbor Ba—Ba separation of 3.8366 (5) Å. The geometry of the chain is defined by a Ba—Ba—Ba angle (φ) of 81.70 (2)° and a Ba—Ba—Ba—Ba dihedral angle (ω) of 180°, indicating that the chains are coplanar. The corresponding zigzag angle in the isostructural low-temperature SrZn₅ phase is slightly larger (φ = 83.05°), while the overall chain topology is retained.

Each Ba atom in BaCu₅ is coordinated by 17 Cu atoms with an average Ba—Cu distance of 3.3966 (6) Å (Fig. 3). The Ba—Ba distance is slightly longer than that reported for BaZn₅ (3.803 Å) and slightly shorter than the corresponding Sr—Sr distance (3.974 Å) in the isostructural SrZn₅ phase. The Cu framework in BaCu₅ is constructed from four crystallographically distinct Cu sites. The shortest Cu—Cu contacts are found around the general position Cu site, with distances ranging from 2.5012 (9) to 2.5404 (10) Å, whereas longer Cu—Ba contacts occur between 3.5163 (7) and 3.6461 (8) Å.

Figure 3
Local coordination around the Ba atoms in the structure. Each Ba atom is bonded to two neighboring Ba atoms and 17 Cu atoms with an average bond distance of 3.398 Å. The Ba—Ba distance is 3.8366 (5) Å, which is slightly longer than the Ba—Ba distance in BaZn₅ and slightly shorter than the Sr—Sr distance in SrZn₅.

3. Database survey

A search of the PDF-5+ database (Kabekkodu et al., 2024 ) for the CaCu₅ structure type returned 2080 entries: 434 of them contained Cu as the transition metal and 11 contained Ba as the alkaline earth metal but no entries contained both Ba and Cu. In contrast, a search for the SrZn₅ structure type returned just four hits, one of them being SrZn₅ itself, highlighting the exceptional rarity of this structure type

4. Synthesis and crystallization

The title compound was synthesized by modification of a previously reported synthesis (Wan et al., 2024 ). Ba beads (Sigma Aldrich 99%) and Cu powder (Thermo Fisher 99%, 325 mesh) were pressed together in a 1:1 stoichiometric ratio in an argon filled glove box. The solids were sealed in a quartz ampoule under vacuum and heated at 873 K for 12 h. The reaction was then cooled down to room temperature over the course of 6 h. After the reaction, a mixture of several phases was present in the melt including single crystals of the layered electride BaCu and several previously unreported and highly disordered barium suboxides (Ba₇O₃) resulting from reaction between Ba and the quartz ampoule. Several unsuccessful attempts were made to synthesize phase-pure samples of BaCu₅ directly in quartz, steel, and niobium crucibles. Single crystals of BaCu₅ were picked out from the melt of the reaction. The broken pieces of the melts were submerged in polybutene oil inside an argon filled glovebox. The crystals were quickly transferred to the goniometer head.

5. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1.

Table 1
Experimental details

Crystal data
Chemical formula	BaCu₅
M_r	455.04
Crystal system, space group	Orthorhombic, Pnma
Temperature (K)	150
a, b, c (Å)	12.8420 (7), 5.0189 (3), 6.5445 (6)
V (Å³)	421.81 (5)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	33.71
Crystal size (mm)	0.13 × 0.08 × 0.02

Data collection
Diffractometer	Bruker AXS D8 Quest
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )
T_min, T_max	0.135, 0.274
No. of measured, independent and observed [I > 2σ(I)] reflections	24524, 1112, 877
R_int	0.080
(sin θ/λ)_max (Å⁻¹)	0.834

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.030, 0.059, 1.09
No. of reflections	1112
No. of parameters	34
Δρ_max, Δρ_min (e Å⁻³)	1.69, −1.76
Computer programs: APEX5 and SAINT (Bruker, 2025 ), SHELXT (Sheldrick, 2015a ), SHELXL2025/1 (Sheldrick, 2015b ) and ShelXle (Hübschle et al., 2011 ).

Supporting information

CCDC reference: 2579957

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989026008248/hb8240sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989026008248/hb8240Isup2.hkl

checkCIF report

Computing details top

Barium pentacopper top

Crystal data top

BaCu₅	D_x = 7.165 Mg m⁻³
M_r = 455.04	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pnma	Cell parameters from 6137 reflections
a = 12.8420 (7) Å	θ = 3.2–35.8°
b = 5.0189 (3) Å	µ = 33.71 mm⁻¹
c = 6.5445 (6) Å	T = 150 K
V = 421.81 (5) Å³	Block, black
Z = 4	0.13 × 0.08 × 0.02 mm
F(000) = 804

Data collection top

Bruker AXS D8 Quest diffractometer	1112 independent reflections
Radiation source: fine focus sealed tube X-ray source	877 reflections with I > 2σ(I)
Triumph curved graphite crystal monochromator	R_int = 0.080
Detector resolution: 7.4074 pixels mm^-1	θ_max = 36.4°, θ_min = 3.2°
ω and phi scans	h = −21→21
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	k = −8→8
T_min = 0.135, T_max = 0.274	l = −10→10
24524 measured reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Primary atom site location: dual
R[F² > 2σ(F²)] = 0.030	Secondary atom site location: difference Fourier map
wR(F²) = 0.059	w = 1/[σ²(F_o²) + (0.0111P)² + 7.083P] where P = (F_o² + 2F_c²)/3
S = 1.09	(Δ/σ)_max < 0.001
1112 reflections	Δρ_max = 1.69 e Å⁻³
34 parameters	Δρ_min = −1.76 e Å⁻³

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
Ba1	0.58888 (3)	0.750000	0.13690 (6)	0.00983 (8)
Cu1	0.48045 (6)	0.750000	0.57102 (13)	0.00970 (14)
Cu2	0.35376 (4)	0.49998 (11)	0.35225 (9)	0.00888 (10)
Cu3	0.28152 (7)	0.750000	0.05359 (12)	0.00979 (15)
Cu4	0.21455 (6)	0.250000	0.16200 (12)	0.00922 (14)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Ba1	0.01055 (14)	0.01004 (15)	0.00890 (14)	0.000	0.00060 (13)	0.000
Cu1	0.0087 (3)	0.0103 (3)	0.0101 (3)	0.000	−0.0008 (3)	0.000
Cu2	0.0100 (2)	0.0077 (2)	0.0089 (2)	−0.00029 (18)	−0.00062 (19)	0.00011 (19)
Cu3	0.0115 (3)	0.0099 (3)	0.0080 (3)	0.000	−0.0009 (3)	0.000
Cu4	0.0098 (3)	0.0099 (3)	0.0080 (3)	0.000	−0.0012 (3)	0.000

Geometric parameters (Å, º) top

Ba1—Cu1	3.1640 (10)	Cu1—Cu2^ix	2.5217 (9)
Ba1—Cu4ⁱ	3.1935 (9)	Cu1—Cu2^vi	2.5217 (9)
Ba1—Cu3ⁱⁱ	3.1974 (9)	Cu1—Cu4^x	2.5740 (11)
Ba1—Cu3ⁱⁱⁱ	3.2590 (6)	Cu1—Cu1^vi	2.7228 (7)
Ba1—Cu3ⁱ	3.2590 (6)	Cu1—Cu1^v	2.7228 (7)
Ba1—Cu4^iv	3.2610 (6)	Cu2—Cu3	2.5012 (9)
Ba1—Cu4ⁱⁱ	3.2610 (6)	Cu2—Cu2^xi	2.5092 (11)
Ba1—Cu1^v	3.2778 (6)	Cu2—Cu2^viii	2.5097 (11)
Ba1—Cu1^vi	3.2778 (6)	Cu2—Cu4	2.5140 (9)
Ba1—Cu2ⁱ	3.5163 (7)	Cu2—Cu3^x	2.5157 (9)
Ba1—Cu2^vii	3.5163 (7)	Cu2—Cu4^x	2.5404 (9)
Ba1—Cu2	3.5606 (7)	Cu3—Cu4^xii	2.5633 (11)
Cu1—Cu2	2.5043 (9)	Cu3—Cu4^xiii	2.7460 (5)
Cu1—Cu2^viii	2.5043 (9)	Cu3—Cu4	2.7460 (5)

Cu1—Ba1—Cu4ⁱ	153.88 (2)	Cu3—Cu2—Ba1ⁱ	62.95 (2)
Cu1—Ba1—Cu3ⁱⁱ	76.80 (2)	Cu1—Cu2—Ba1ⁱ	124.28 (3)
Cu4ⁱ—Ba1—Cu3ⁱⁱ	77.08 (2)	Cu2^xi—Cu2—Ba1ⁱ	69.096 (9)
Cu1—Ba1—Cu3ⁱⁱⁱ	124.627 (16)	Cu2^viii—Cu2—Ba1ⁱ	110.903 (9)
Cu4ⁱ—Ba1—Cu3ⁱⁱⁱ	50.361 (13)	Cu4—Cu2—Ba1ⁱ	61.31 (2)
Cu3ⁱⁱ—Ba1—Cu3ⁱⁱⁱ	81.212 (10)	Cu3^x—Cu2—Ba1ⁱ	116.33 (2)
Cu1—Ba1—Cu3ⁱ	124.627 (16)	Cu1^vi—Cu2—Ba1ⁱ	80.03 (2)
Cu4ⁱ—Ba1—Cu3ⁱ	50.361 (13)	Cu4^x—Cu2—Ba1ⁱ	167.17 (3)
Cu3ⁱⁱ—Ba1—Cu3ⁱ	81.212 (10)	Cu3—Cu2—Ba1	80.12 (2)
Cu3ⁱⁱⁱ—Ba1—Cu3ⁱ	100.71 (3)	Cu1—Cu2—Ba1	59.92 (2)
Cu1—Ba1—Cu4^iv	81.686 (19)	Cu2^xi—Cu2—Ba1	110.636 (9)
Cu4ⁱ—Ba1—Cu4^iv	81.722 (10)	Cu2^viii—Cu2—Ba1	69.365 (9)
Cu3ⁱⁱ—Ba1—Cu4^iv	50.312 (12)	Cu4—Cu2—Ba1	125.65 (3)
Cu3ⁱⁱⁱ—Ba1—Cu4^iv	46.300 (19)	Cu3^x—Cu2—Ba1	165.63 (3)
Cu3ⁱ—Ba1—Cu4^iv	119.62 (2)	Cu1^vi—Cu2—Ba1	62.497 (19)
Cu1—Ba1—Cu4ⁱⁱ	81.686 (19)	Cu4^x—Cu2—Ba1	115.76 (2)
Cu4ⁱ—Ba1—Cu4ⁱⁱ	81.722 (10)	Ba1ⁱ—Cu2—Ba1	65.654 (13)
Cu3ⁱⁱ—Ba1—Cu4ⁱⁱ	50.312 (13)	Cu3—Cu2—Ba1^xiv	59.59 (2)
Cu3ⁱⁱⁱ—Ba1—Cu4ⁱⁱ	119.62 (2)	Cu1—Cu2—Ba1^xiv	115.14 (2)
Cu3ⁱ—Ba1—Cu4ⁱⁱ	46.300 (19)	Cu2^xi—Cu2—Ba1^xiv	110.245 (9)
Cu4^iv—Ba1—Cu4ⁱⁱ	100.62 (3)	Cu2^viii—Cu2—Ba1^xiv	69.755 (9)
Cu1—Ba1—Cu1^v	49.969 (13)	Cu4—Cu2—Ba1^xiv	61.011 (18)
Cu4ⁱ—Ba1—Cu1^v	124.885 (15)	Cu3^x—Cu2—Ba1^xiv	60.956 (19)
Cu3ⁱⁱ—Ba1—Cu1^v	80.84 (2)	Cu1^vi—Cu2—Ba1^xiv	163.78 (3)
Cu3ⁱⁱⁱ—Ba1—Cu1^v	76.838 (17)	Cu4^x—Cu2—Ba1^xiv	59.30 (2)
Cu3ⁱ—Ba1—Cu1^v	162.05 (3)	Ba1ⁱ—Cu2—Ba1^xiv	109.741 (17)
Cu4^iv—Ba1—Cu1^v	46.364 (19)	Ba1—Cu2—Ba1^xiv	132.941 (16)
Cu4ⁱⁱ—Ba1—Cu1^v	119.22 (2)	Cu3—Cu2—Ba1^vi	164.61 (3)
Cu1—Ba1—Cu1^vi	49.969 (13)	Cu1—Cu2—Ba1^vi	61.115 (19)
Cu4ⁱ—Ba1—Cu1^vi	124.885 (15)	Cu2^xi—Cu2—Ba1^vi	69.874 (9)
Cu3ⁱⁱ—Ba1—Cu1^vi	80.84 (2)	Cu2^viii—Cu2—Ba1^vi	110.127 (9)
Cu3ⁱⁱⁱ—Ba1—Cu1^vi	162.05 (3)	Cu4—Cu2—Ba1^vi	115.22 (2)
Cu3ⁱ—Ba1—Cu1^vi	76.838 (17)	Cu3^x—Cu2—Ba1^vi	59.18 (2)
Cu4^iv—Ba1—Cu1^vi	119.22 (2)	Cu1^vi—Cu2—Ba1^vi	58.38 (2)
Cu4ⁱⁱ—Ba1—Cu1^vi	46.364 (19)	Cu4^x—Cu2—Ba1^vi	60.531 (19)
Cu1^v—Ba1—Cu1^vi	99.92 (3)	Ba1ⁱ—Cu2—Ba1^vi	132.043 (17)
Cu1—Ba1—Cu2ⁱ	155.461 (14)	Ba1—Cu2—Ba1^vi	108.234 (16)
Cu4ⁱ—Ba1—Cu2ⁱ	43.679 (16)	Ba1^xiv—Cu2—Ba1^vi	106.895 (17)
Cu3ⁱⁱ—Ba1—Cu2ⁱ	114.50 (2)	Cu2^viii—Cu3—Cu2	60.23 (3)
Cu3ⁱⁱⁱ—Ba1—Cu2ⁱ	79.602 (18)	Cu2^viii—Cu3—Cu2^xii	156.30 (4)
Cu3ⁱ—Ba1—Cu2ⁱ	43.118 (17)	Cu2—Cu3—Cu2^xii	114.536 (16)
Cu4^iv—Ba1—Cu2ⁱ	122.57 (2)	Cu2^viii—Cu3—Cu2^xv	114.536 (16)
Cu4ⁱⁱ—Ba1—Cu2ⁱ	89.381 (18)	Cu2—Cu3—Cu2^xv	156.30 (4)
Cu1^v—Ba1—Cu2ⁱ	149.426 (17)	Cu2^xii—Cu3—Cu2^xv	59.83 (3)
Cu1^vi—Ba1—Cu2ⁱ	108.340 (16)	Cu2^viii—Cu3—Cu4^xii	140.72 (3)
Cu1—Ba1—Cu2^vii	155.461 (14)	Cu2—Cu3—Cu4^xii	140.72 (3)
Cu4ⁱ—Ba1—Cu2^vii	43.679 (16)	Cu2^xii—Cu3—Cu4^xii	59.33 (3)
Cu3ⁱⁱ—Ba1—Cu2^vii	114.50 (2)	Cu2^xv—Cu3—Cu4^xii	59.33 (3)
Cu3ⁱⁱⁱ—Ba1—Cu2^vii	43.118 (17)	Cu2^viii—Cu3—Cu4^xiii	57.03 (2)
Cu3ⁱ—Ba1—Cu2^vii	79.602 (18)	Cu2—Cu3—Cu4^xiii	111.88 (3)
Cu4^iv—Ba1—Cu2^vii	89.381 (18)	Cu2^xii—Cu3—Cu4^xiii	112.01 (3)
Cu4ⁱⁱ—Ba1—Cu2^vii	122.57 (2)	Cu2^xv—Cu3—Cu4^xiii	57.54 (2)
Cu1^v—Ba1—Cu2^vii	108.340 (16)	Cu4^xii—Cu3—Cu4^xiii	105.34 (2)
Cu1^vi—Ba1—Cu2^vii	149.426 (17)	Cu2^viii—Cu3—Cu4	111.88 (3)
Cu2ⁱ—Ba1—Cu2^vii	41.807 (19)	Cu2—Cu3—Cu4	57.03 (2)
Cu1—Ba1—Cu2	43.227 (16)	Cu2^xii—Cu3—Cu4	57.54 (2)
Cu4ⁱ—Ba1—Cu2	155.890 (14)	Cu2^xv—Cu3—Cu4	112.01 (3)
Cu3ⁱⁱ—Ba1—Cu2	113.91 (2)	Cu4^xii—Cu3—Cu4	105.34 (2)
Cu3ⁱⁱⁱ—Ba1—Cu2	148.851 (17)	Cu4^xiii—Cu3—Cu4	132.09 (4)
Cu3ⁱ—Ba1—Cu2	108.245 (15)	Cu2^viii—Cu3—Ba1^xiv	77.99 (3)
Cu4^iv—Ba1—Cu2	122.08 (2)	Cu2—Cu3—Ba1^xiv	77.99 (3)
Cu4ⁱⁱ—Ba1—Cu2	89.354 (17)	Cu2^xii—Cu3—Ba1^xiv	78.32 (3)
Cu1^v—Ba1—Cu2	78.967 (18)	Cu2^xv—Cu3—Ba1^xiv	78.32 (3)
Cu1^vi—Ba1—Cu2	43.030 (17)	Cu4^xii—Cu3—Ba1^xiv	130.44 (4)
Cu2ⁱ—Ba1—Cu2	114.346 (13)	Cu4^xiii—Cu3—Ba1^xiv	66.05 (2)
Cu2^vii—Ba1—Cu2	131.585 (13)	Cu4—Cu3—Ba1^xiv	66.05 (2)
Cu2—Cu1—Cu2^viii	60.14 (3)	Cu2^viii—Cu3—Ba1ⁱⁱⁱ	73.931 (19)
Cu2—Cu1—Cu2^ix	155.73 (4)	Cu2—Cu3—Ba1ⁱⁱⁱ	119.72 (3)
Cu2^viii—Cu1—Cu2^ix	114.397 (19)	Cu2^xii—Cu3—Ba1ⁱⁱⁱ	122.43 (3)
Cu2—Cu1—Cu2^vi	114.397 (19)	Cu2^xv—Cu3—Ba1ⁱⁱⁱ	76.602 (19)
Cu2^viii—Cu1—Cu2^vi	155.73 (4)	Cu4^xii—Cu3—Ba1ⁱⁱⁱ	66.89 (2)
Cu2^ix—Cu1—Cu2^vi	59.67 (3)	Cu4^xiii—Cu3—Ba1ⁱⁱⁱ	63.582 (17)
Cu2—Cu1—Cu4^x	60.01 (3)	Cu4—Cu3—Ba1ⁱⁱⁱ	164.25 (3)
Cu2^viii—Cu1—Cu4^x	60.01 (3)	Ba1^xiv—Cu3—Ba1ⁱⁱⁱ	129.602 (13)
Cu2^ix—Cu1—Cu4^x	140.84 (3)	Cu2^viii—Cu3—Ba1ⁱ	119.72 (3)
Cu2^vi—Cu1—Cu4^x	140.84 (3)	Cu2—Cu3—Ba1ⁱ	73.931 (19)
Cu2—Cu1—Cu1^vi	57.51 (3)	Cu2^xii—Cu3—Ba1ⁱ	76.602 (19)
Cu2^viii—Cu1—Cu1^vi	112.73 (5)	Cu2^xv—Cu3—Ba1ⁱ	122.43 (3)
Cu2^ix—Cu1—Cu1^vi	111.77 (5)	Cu4^xii—Cu3—Ba1ⁱ	66.89 (2)
Cu2^vi—Cu1—Cu1^vi	56.89 (3)	Cu4^xiii—Cu3—Ba1ⁱ	164.25 (3)
Cu4^x—Cu1—Cu1^vi	104.97 (3)	Cu4—Cu3—Ba1ⁱ	63.583 (17)
Cu2—Cu1—Cu1^v	112.73 (5)	Ba1^xiv—Cu3—Ba1ⁱ	129.602 (13)
Cu2^viii—Cu1—Cu1^v	57.51 (3)	Ba1ⁱⁱⁱ—Cu3—Ba1ⁱ	100.71 (3)
Cu2^ix—Cu1—Cu1^v	56.89 (3)	Cu2^xi—Cu4—Cu2	59.87 (3)
Cu2^vi—Cu1—Cu1^v	111.77 (5)	Cu2^xi—Cu4—Cu2^xvi	113.220 (18)
Cu4^x—Cu1—Cu1^v	104.97 (3)	Cu2—Cu4—Cu2^xvi	152.53 (4)
Cu1^vi—Cu1—Cu1^v	134.34 (7)	Cu2^xi—Cu4—Cu2^xii	152.53 (4)
Cu2—Cu1—Ba1	76.85 (3)	Cu2—Cu4—Cu2^xii	113.220 (18)
Cu2^viii—Cu1—Ba1	76.85 (3)	Cu2^xvi—Cu4—Cu2^xii	59.20 (3)
Cu2^ix—Cu1—Ba1	78.89 (3)	Cu2^xi—Cu4—Cu3^x	59.39 (3)
Cu2^vi—Cu1—Ba1	78.89 (3)	Cu2—Cu4—Cu3^x	59.39 (3)
Cu4^x—Cu1—Ba1	129.48 (4)	Cu2^xvi—Cu4—Cu3^x	143.57 (3)
Cu1^vi—Cu1—Ba1	67.19 (3)	Cu2^xii—Cu4—Cu3^x	143.57 (3)
Cu1^v—Cu1—Ba1	67.19 (3)	Cu2^xi—Cu4—Cu1^xii	143.74 (3)
Cu2—Cu1—Ba1^v	122.72 (3)	Cu2—Cu4—Cu1^xii	143.74 (3)
Cu2^viii—Cu1—Ba1^v	76.898 (19)	Cu2^xvi—Cu4—Cu1^xii	58.63 (3)
Cu2^ix—Cu1—Ba1^v	74.474 (19)	Cu2^xii—Cu4—Cu1^xii	58.63 (3)
Cu2^vi—Cu1—Ba1^v	119.61 (3)	Cu3^x—Cu4—Cu1^xii	104.50 (4)
Cu4^x—Cu1—Ba1^v	66.475 (19)	Cu2^xi—Cu4—Cu3	111.18 (3)
Cu1^vi—Cu1—Ba1^v	162.71 (5)	Cu2—Cu4—Cu3	56.58 (2)
Cu1^v—Cu1—Ba1^v	62.84 (2)	Cu2^xvi—Cu4—Cu3	110.69 (3)
Ba1—Cu1—Ba1^v	130.031 (13)	Cu2^xii—Cu4—Cu3	56.67 (2)
Cu2—Cu1—Ba1^vi	76.898 (19)	Cu3^x—Cu4—Cu3	104.61 (2)
Cu2^viii—Cu1—Ba1^vi	122.72 (3)	Cu1^xii—Cu4—Cu3	104.18 (2)
Cu2^ix—Cu1—Ba1^vi	119.61 (3)	Cu2^xi—Cu4—Cu3^xvii	56.58 (2)
Cu2^vi—Cu1—Ba1^vi	74.474 (19)	Cu2—Cu4—Cu3^xvii	111.18 (3)
Cu4^x—Cu1—Ba1^vi	66.475 (19)	Cu2^xvi—Cu4—Cu3^xvii	56.67 (2)
Cu1^vi—Cu1—Ba1^vi	62.84 (2)	Cu2^xii—Cu4—Cu3^xvii	110.70 (3)
Cu1^v—Cu1—Ba1^vi	162.71 (5)	Cu3^x—Cu4—Cu3^xvii	104.61 (2)
Ba1—Cu1—Ba1^vi	130.031 (13)	Cu1^xii—Cu4—Cu3^xvii	104.18 (2)
Ba1^v—Cu1—Ba1^vi	99.92 (3)	Cu3—Cu4—Cu3^xvii	132.09 (4)
Cu3—Cu2—Cu1	115.87 (3)	Cu2^xi—Cu4—Ba1ⁱ	75.01 (2)
Cu3—Cu2—Cu2^xi	120.112 (16)	Cu2—Cu4—Ba1ⁱ	75.01 (2)
Cu1—Cu2—Cu2^xi	120.072 (16)	Cu2^xvi—Cu4—Ba1ⁱ	77.54 (3)
Cu3—Cu2—Cu2^viii	59.887 (16)	Cu2^xii—Cu4—Ba1ⁱ	77.54 (3)
Cu1—Cu2—Cu2^viii	59.929 (16)	Cu3^x—Cu4—Ba1ⁱ	126.65 (4)
Cu2^xi—Cu2—Cu2^viii	180.0	Cu1^xii—Cu4—Ba1ⁱ	128.85 (4)
Cu3—Cu2—Cu4	66.39 (2)	Cu3—Cu4—Ba1ⁱ	66.06 (2)
Cu1—Cu2—Cu4	174.38 (4)	Cu3^xvii—Cu4—Ba1ⁱ	66.06 (2)
Cu2^xi—Cu2—Cu4	60.062 (15)	Cu2^xi—Cu4—Ba1^xviii	76.585 (18)
Cu2^viii—Cu2—Cu4	119.936 (15)	Cu2—Cu4—Ba1^xviii	122.42 (3)
Cu3—Cu2—Cu3^x	113.79 (2)	Cu2^xvi—Cu4—Ba1^xviii	76.763 (18)
Cu1—Cu2—Cu3^x	113.52 (3)	Cu2^xii—Cu4—Ba1^xviii	122.09 (3)
Cu2^xi—Cu2—Cu3^x	60.085 (16)	Cu3^x—Cu4—Ba1^xviii	66.81 (2)
Cu2^viii—Cu2—Cu3^x	119.915 (16)	Cu1^xii—Cu4—Ba1^xviii	67.162 (19)
Cu4—Cu2—Cu3^x	61.28 (3)	Cu3—Cu4—Ba1^xviii	164.27 (3)
Cu3—Cu2—Cu1^vi	135.92 (4)	Cu3^xvii—Cu4—Ba1^xviii	63.642 (17)
Cu1—Cu2—Cu1^vi	65.604 (19)	Ba1ⁱ—Cu4—Ba1^xviii	129.673 (13)
Cu2^xi—Cu2—Cu1^vi	60.164 (15)	Cu2^xi—Cu4—Ba1^xiv	122.42 (3)
Cu2^viii—Cu2—Cu1^vi	119.837 (15)	Cu2—Cu4—Ba1^xiv	76.585 (18)
Cu4—Cu2—Cu1^vi	116.79 (3)	Cu2^xvi—Cu4—Ba1^xiv	122.09 (3)
Cu3^x—Cu2—Cu1^vi	103.34 (3)	Cu2^xii—Cu4—Ba1^xiv	76.763 (19)
Cu3—Cu2—Cu4^x	104.34 (3)	Cu3^x—Cu4—Ba1^xiv	66.81 (2)
Cu1—Cu2—Cu4^x	61.36 (3)	Cu1^xii—Cu4—Ba1^xiv	67.162 (19)
Cu2^xi—Cu2—Cu4^x	119.601 (15)	Cu3—Cu4—Ba1^xiv	63.642 (17)
Cu2^viii—Cu2—Cu4^x	60.399 (15)	Cu3^xvii—Cu4—Ba1^xiv	164.27 (3)
Cu4—Cu2—Cu4^x	113.34 (2)	Ba1ⁱ—Cu4—Ba1^xiv	129.673 (13)
Cu3^x—Cu2—Cu4^x	65.79 (2)	Ba1^xviii—Cu4—Ba1^xiv	100.62 (3)
Cu1^vi—Cu2—Cu4^x	112.24 (3)

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

Acknowledgements

This material is based upon work supported by the National Science Foundation through the Major Research Instrumentation Program under grant No. CHE 1625543 (funding for the single-crystal X-ray diffractometer). We thank the College of Science, Purdue University, for support for X-ray detector upgrades through the 2020 Laboratory and University Core Facility Research Equipment Program.

References

Boeije, M. F. J., Delczeg-Czirjak, E. K., van Dijk, N. H., Eriksson, O. & Brück, E. (2017). J. Alloys Compd. 722, 549–554. Web of Science CrossRef CAS Google Scholar
Bruker (2025). APEX5 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Bruzzone, G. (1971). J. Less-Common Met. 25, 361–366. CrossRef ICSD CAS Web of Science Google Scholar
Bruzzone, G., Ferretti, M. & Merlo, F. (1985). J. Less-Common Met. 114, 305–310. CrossRef ICSD CAS Web of Science Google Scholar
Bruzzone, G. & Merlo, F. (1983). J. Less-Common Met. 92, 75–79. CrossRef ICSD CAS Web of Science Google Scholar
Hou, Y., Xu, Z., Peng, S., Rong, C., Liu, J. P. & Sun, S. (2007). Adv. Mater. 19, 3349–3352. Web of Science CrossRef CAS Google Scholar
Hübschle, C. B., Sheldrick, G. M. & Dittrich, B. (2011). J. Appl. Cryst. 44, 1281–1284. Web of Science CrossRef IUCr Journals Google Scholar
Kabekkodu, S. N., Dosen, A. & Blanton, T. N. (2024). Powder Diffr. 39, 47–59. Web of Science CrossRef CAS Google Scholar
Krause, L., Herbst-Irmer, R., Sheldrick, G. M. & Stalke, D. (2015). J. Appl. Cryst. 48, 3–10. Web of Science CSD CrossRef ICSD CAS IUCr Journals Google Scholar
Liang, G., Huot, J. & Schulz, R. (2001). J. Alloys Compd. 321, 146–150. Web of Science CrossRef CAS Google Scholar
Nakamura, H., Kitaoka, Y., Inoue, M., Asayama, K. & Ōnuki, Y. (1990). J. Magn. Magn. Mater. 90–91, 459–460. CrossRef CAS Web of Science Google Scholar
Schwickert, C. & Pöttgen, R. (2014). Z. Naturforsch. B 69, 674–680. Web of Science CrossRef CAS Google Scholar
Sheldrick, G. M. (2015a). Acta Cryst. A71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2015b). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Simura, R. & Yamane, H. (2019). Acta Cryst. E75, 1490–1493. CrossRef IUCr Journals Google Scholar
Wan, B., Yuan, Y., Zheng, L., Xu, Y., Zhao, S., Liu, K., Huang, D., Wu, L., Zhang, Z., Wang, G., Li, J., Zhang, S. & Gou, H. (2024). J. Am. Chem. Soc. 146, 17508–17516. Web of Science CrossRef CAS PubMed Google Scholar
Xu, J., Chen, X., Zhu, W., Zhang, W., Cui, H., Zhu, S., Liu, J., Liu, H., Yan, K. & Cheng, H. (2022). Int. J. Hydrogen Energy 47, 22495–22509. Web of Science CrossRef CAS Google Scholar
Zhou, P., Zhang, J., Bi, J., Xiao, X., Cao, Z., Zhan, L., Shen, H., Lu, M., Li, Z., Zhao, Y., Wang, L., Yan, M. & Chen, L. (2023). J. Mater. Chem. A 11, 25963–25972. Web of Science CrossRef CAS Google Scholar

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