Redetermination of Ba₂CdTe₃ from single-crystal X-ray data

The previous structure determination of the title compound, dibarium tritelluridocadmate, was based on powder X-ray diffraction data [Wang & DiSalvo (1999). J. Solid State Chem. 148, 464–467]. In the current redetermination from single-crystal X-ray data, all atoms were refined with anisotropic displacement parameters. The previous structure report is generally confirmed, but with some differences in bond lengths. Ba₂CdTe₃ is isotypic with Ba₂MX₃ (M = Mn, Cd; X = S, Se) and features ¹_∞[CdTe_2/2Te_2/1]⁴⁻ chains of corner-sharing CdTe₄ tetra­hedra running parallel [010]. The two Ba²⁺ cations are located between the chains, both within distorted monocapped trigonal–prismatic coordination polyhedra. All atoms in the structure are located on a mirror plane.

Related literature

For the previous determination of Ba₂CdTe₃, see: Wang & DiSalvo (1999). For isotypic compounds, see: Grey & Steinfink (1971) for Ba₂MnS₃ and Ba₂MnSe₃; Iglesias et al. (1974) for Ba₂CdSe₃ and Ba₂CdS₃.

Experimental

Crystal data

• Ba₂CdTe₃

• M_r = 769.88

• Orthorhombic, P n m a

• a = 9.8405 (2) Å

• b = 4.7502 (1) Å

• c = 19.1008 (4) Å

• V = 892.85 (3) ų

• Z = 4

• Mo Kα radiation

• μ = 20.59 mm⁻¹

• T = 293 K

• 0.07 × 0.03 × 0.03 mm

Data collection

• Bruker APEXII CCD diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 2005) T_min = 0.348, T_max = 0.627

• 4014 measured reflections

• 1098 independent reflections

• 858 reflections with I > 2σ(I)

• R_int = 0.031

Refinement

• R[F² > 2σ(F²)] = 0.025

• wR(F²) = 0.041

• S = 0.99

• 1098 reflections

• 38 parameters

• Δρ_max = 1.44 e Å⁻³

• Δρ_min = −1.27 e Å⁻³

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supporting information

S1. Comment

Single crystals of Ba₂CdTe₃ were obtained unintentionally from a Bi-flux reactions for exploration of possible new ternary phases in the Ba—Cd—Te system.

The structure of Ba₂CdTe₃ is isotypic with Ba₂MnX₃ (X = S, Se; Grey & Steinfink, 1971) and Ba₂CdX₃ (X = S, Se; Iglesias et al., 1974). The structural set-up can be described as a packing of polyanionic chains composed of corner-sharing CdTe₄ tetrahedra. These chains run parallel to [010]; inbetween the chains the two Ba²⁺ cations are located (Fig. 1), both with a coordination number of 7 and surrounded in form of monocapped trigonal-prismatic polyhedra of Te atoms. All atoms are located on a mirror plane x, 1/4, z (Wyckoff symbol 4c).

In comparison with the previous structure model on basis of powder X-ray data (Wang & DiSalvo, 1999), the most important improvement of the current redetermination is reflected in the higher precision of the atomic coordinates and the use of anisotropic displacemenet parameters for all atoms. Although the coordination spheres of Cd and the two Ba atoms can still be described as a distorted CdTe₄ tetrahedron and two distorted monocapped trigonal BaTe₇ prisms, respectively, the results of the redetermination indicate some differences in terms of Cd—Te and Ba—Te bond lengths (mean σ for the bond length of the powder model in the range 0.003 Å; 0.0006 for the current model). For example, the longest Ba—Te bonds are 3.6722 (8) and 3.6796 (8) Å for Ba1 and Ba2. The previous powder study revealed distances of 3.638 (5) and 3.500 (5) Å, respectively.

Related literature

For the previous determination of Ba₂CdTe₃, see: Wang & DiSalvo (1999). For isotypic compounds, see: Grey & Steinfink (1971) for Ba₂MnS₃ and Ba₂MnSe₃; Iglesias et al. (1974) for Ba₂CdSe₃ and Ba₂CdS₃.

S2. Experimental

The title compound was synthesized through a high temperature metal flux reaction. All starting elements were handled inside an Argon-filled glove box with controlled oxygen and moisture levels below 0.1 p.p.m.. The reaction conditions were optimized as follows: Ba, Cd, Te and Bi in a molar ratio of 2:1:3:10 were loaded in an alumina crucible, which were subsequently flame-sealed in a fused silica tube. The reactants were heated quickly to 973 K and allowed to dwell at this temperature for 20 h. After a slow cooling process down to 773 K at a rate of 5 K/h and the removal of the Bi flux by centrifugation, high-quality single crystals of Ba₂CdTe₃ were obtained.

S3. Refinement

The full occupancies for all sites were verified by freeing the site occupation factor for an individual atom, while other remaining parameters were kept fixed. This proved that all positions are fully occupied with corresponding deviations from full occupancy within 3σ. The residual electron densities show a maximum peak of 1.44 e/ų and a minimum hole of -1.27 e/ų, which are 0.86 and 0.81 Å from Te3 and Te2, respectively.

Computing details

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

Fig. 1. View of the structure of Ba2CdTe3 along the b-axis. The barium, cadmium and tellurium atoms are plotted as purple, green and red ellipsoids, respectively. Ellipsoids are drawn at the 90% probability level.

dibarium tritelluridocadmate

Crystal data

Ba2CdTe3	F(000) = 1264
Mr = 769.88	Dx = 5.727 Mg m^−3
Orthorhombic, Pnma	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2n	Cell parameters from 1715 reflections
a = 9.8405 (2) Å	θ = 3.0–28.2°
b = 4.7502 (1) Å	µ = 20.59 mm^−1
c = 19.1008 (4) Å	T = 293 K
V = 892.85 (3) Å^3	Needle, red
Z = 4	0.07 × 0.03 × 0.03 mm

Data collection

Bruker APEXII CCD diffractometer	1098 independent reflections
Radiation source: fine-focus sealed tube	858 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.031
φ and ω scans	θmax = 27.1°, θmin = 2.1°
Absorption correction: multi-scan (SADABS; Bruker, 2005)	h = −12→9
Tmin = 0.348, Tmax = 0.627	k = −3→6
4014 measured reflections	l = −24→15

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.025	w = 1/[σ^2(Fo^2) + (0.0142P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.041	(Δ/σ)max = 0.001
S = 0.99	Δρmax = 1.44 e Å^−3
1098 reflections	Δρmin = −1.27 e Å^−3
38 parameters	Extinction correction: SHELXTL (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.00112 (6)

Special details

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

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Ba1	0.07317 (6)	0.2500	0.78653 (3)	0.01857 (16)
Ba2	0.24597 (6)	0.2500	0.03873 (3)	0.01918 (16)
Cd1	0.12996 (7)	0.2500	0.36470 (3)	0.01947 (18)
Te1	0.01147 (6)	0.2500	0.59692 (3)	0.01802 (17)
Te2	0.19335 (6)	0.2500	0.22108 (3)	0.01748 (16)
Te3	0.38656 (6)	0.2500	0.42865 (3)	0.01745 (17)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ba1	0.0190 (3)	0.0171 (3)	0.0196 (4)	0.000	−0.0003 (3)	0.000
Ba2	0.0209 (3)	0.0191 (3)	0.0175 (3)	0.000	−0.0013 (3)	0.000
Cd1	0.0197 (4)	0.0201 (4)	0.0186 (4)	0.000	0.0014 (3)	0.000
Te1	0.0187 (4)	0.0154 (3)	0.0200 (4)	0.000	0.0024 (3)	0.000
Te2	0.0178 (4)	0.0203 (3)	0.0144 (4)	0.000	−0.0008 (3)	0.000
Te3	0.0158 (4)	0.0200 (3)	0.0165 (4)	0.000	0.0004 (3)	0.000

Geometric parameters (Å, º)

Ba1—Te2^i	3.5331 (6)	Cd1—Te1^iii	2.8488 (5)
Ba1—Te2^ii	3.5331 (6)	Cd1—Te1^iv	2.8488 (5)
Ba1—Te2^iii	3.5413 (6)	Te1—Cd1^iii	2.8488 (5)
Ba1—Te2^iv	3.5413 (6)	Te1—Cd1^iv	2.8488 (5)
Ba1—Te3^i	3.6287 (6)	Te1—Ba2^i	3.5459 (6)
Ba1—Te3^ii	3.6287 (6)	Te1—Ba2^ii	3.5459 (6)
Ba1—Te1	3.6722 (8)	Te1—Ba2^vii	3.6796 (8)
Ba2—Te3^v	3.4297 (6)	Te2—Ba1^vi	3.5331 (6)
Ba2—Te3^vi	3.4297 (6)	Te2—Ba1^v	3.5331 (6)
Ba2—Te2	3.5213 (8)	Te2—Ba1^iii	3.5413 (6)
Ba2—Te1^vi	3.5459 (6)	Te2—Ba1^iv	3.5413 (6)
Ba2—Te1^v	3.5459 (6)	Te3—Ba2^i	3.4297 (6)
Ba2—Te3^vii	3.5913 (8)	Te3—Ba2^ii	3.4297 (6)
Ba2—Te1^viii	3.6796 (8)	Te3—Ba2^viii	3.5913 (8)
Cd1—Te3	2.8050 (9)	Te3—Ba1^v	3.6287 (6)
Cd1—Te2	2.8133 (9)	Te3—Ba1^vi	3.6287 (6)
Te2^i—Ba1—Te2^ii	84.480 (18)	Te1^iii—Cd1—Te1^iv	112.97 (3)
Te2^i—Ba1—Te2^iii	156.629 (18)	Cd1^iii—Te1—Cd1^iv	112.97 (3)
Te2^ii—Ba1—Te2^iii	90.930 (5)	Cd1^iii—Te1—Ba2^i	165.46 (2)
Te2^i—Ba1—Te2^iv	90.930 (5)	Cd1^iv—Te1—Ba2^i	81.436 (14)
Te2^ii—Ba1—Te2^iv	156.629 (18)	Cd1^iii—Te1—Ba2^ii	81.436 (14)
Te2^iii—Ba1—Te2^iv	84.241 (18)	Cd1^iv—Te1—Ba2^ii	165.46 (2)
Te2^i—Ba1—Te3^i	75.741 (13)	Ba2^i—Te1—Ba2^ii	84.104 (18)
Te2^ii—Ba1—Te3^i	129.32 (2)	Cd1^iii—Te1—Ba1	80.038 (19)
Te2^iii—Ba1—Te3^i	123.41 (2)	Cd1^iv—Te1—Ba1	80.038 (19)
Te2^iv—Ba1—Te3^i	70.888 (14)	Ba2^i—Te1—Ba1	101.413 (18)
Te2^i—Ba1—Te3^ii	129.32 (2)	Ba2^ii—Te1—Ba1	101.413 (18)
Te2^ii—Ba1—Te3^ii	75.741 (13)	Cd1^iii—Te1—Ba2^vii	80.46 (2)
Te2^iii—Ba1—Te3^ii	70.888 (14)	Cd1^iv—Te1—Ba2^vii	80.46 (2)
Te2^iv—Ba1—Te3^ii	123.41 (2)	Ba2^i—Te1—Ba2^vii	104.904 (17)
Te3^i—Ba1—Te3^ii	81.769 (17)	Ba2^ii—Te1—Ba2^vii	104.904 (17)
Te2^i—Ba1—Te1	76.026 (15)	Ba1—Te1—Ba2^vii	144.28 (2)
Te2^ii—Ba1—Te1	76.026 (15)	Cd1—Te2—Ba2	175.65 (3)
Te2^iii—Ba1—Te1	80.624 (16)	Cd1—Te2—Ba1^vi	78.412 (18)
Te2^iv—Ba1—Te1	80.624 (16)	Ba2—Te2—Ba1^vi	104.737 (17)
Te3^i—Ba1—Te1	139.101 (8)	Cd1—Te2—Ba1^v	78.412 (18)
Te3^ii—Ba1—Te1	139.101 (8)	Ba2—Te2—Ba1^v	104.737 (17)
Te3^v—Ba2—Te3^vi	87.658 (19)	Ba1^vi—Te2—Ba1^v	84.480 (18)
Te3^v—Ba2—Te2	123.399 (16)	Cd1—Te2—Ba1^iii	82.866 (18)
Te3^vi—Ba2—Te2	123.399 (16)	Ba2—Te2—Ba1^iii	93.918 (17)
Te3^v—Ba2—Te1^vi	155.78 (2)	Ba1^vi—Te2—Ba1^iii	161.261 (19)
Te3^vi—Ba2—Te1^vi	89.100 (12)	Ba1^v—Te2—Ba1^iii	92.594 (5)
Te2—Ba2—Te1^vi	77.814 (17)	Cd1—Te2—Ba1^iv	82.866 (18)
Te3^v—Ba2—Te1^v	89.100 (12)	Ba2—Te2—Ba1^iv	93.918 (17)
Te3^vi—Ba2—Te1^v	155.78 (2)	Ba1^vi—Te2—Ba1^iv	92.594 (5)
Te2—Ba2—Te1^v	77.814 (17)	Ba1^v—Te2—Ba1^iv	161.261 (19)
Te1^vi—Ba2—Te1^v	84.104 (18)	Ba1^iii—Te2—Ba1^iv	84.240 (18)
Te3^v—Ba2—Te3^vii	74.447 (16)	Cd1—Te3—Ba2^i	85.679 (19)
Te3^vi—Ba2—Te3^vii	74.447 (16)	Cd1—Te3—Ba2^ii	85.679 (19)
Te2—Ba2—Te3^vii	71.552 (17)	Ba2^i—Te3—Ba2^ii	87.658 (19)
Te1^vi—Ba2—Te3^vii	127.482 (15)	Cd1—Te3—Ba2^viii	164.18 (3)
Te1^v—Ba2—Te3^vii	127.482 (15)	Ba2^i—Te3—Ba2^viii	105.553 (16)
Te3^v—Ba2—Te1^viii	80.695 (16)	Ba2^ii—Te3—Ba2^viii	105.553 (16)
Te3^vi—Ba2—Te1^viii	80.695 (16)	Cd1—Te3—Ba1^v	76.852 (18)
Te2—Ba2—Te1^viii	143.22 (2)	Ba2^i—Te3—Ba1^v	162.44 (2)
Te1^vi—Ba2—Te1^viii	75.096 (17)	Ba2^ii—Te3—Ba1^v	92.687 (10)
Te1^v—Ba2—Te1^viii	75.096 (17)	Ba2^viii—Te3—Ba1^v	91.275 (17)
Te3^vii—Ba2—Te1^viii	145.23 (2)	Cd1—Te3—Ba1^vi	76.852 (18)
Te3—Cd1—Te2	103.01 (3)	Ba2^i—Te3—Ba1^vi	92.687 (10)
Te3—Cd1—Te1^iii	109.13 (2)	Ba2^ii—Te3—Ba1^vi	162.44 (2)
Te2—Cd1—Te1^iii	111.05 (2)	Ba2^viii—Te3—Ba1^vi	91.275 (17)
Te3—Cd1—Te1^iv	109.13 (2)	Ba1^v—Te3—Ba1^vi	81.769 (17)
Te2—Cd1—Te1^iv	111.05 (2)

Symmetry codes: (i) −x+1/2, −y+1, z+1/2; (ii) −x+1/2, −y, z+1/2; (iii) −x, −y, −z+1; (iv) −x, −y+1, −z+1; (v) −x+1/2, −y, z−1/2; (vi) −x+1/2, −y+1, z−1/2; (vii) x−1/2, y, −z+1/2; (viii) x+1/2, y, −z+1/2.