Dineodymium tritelluride, Nd₂Te₃

From a single-crystal study, Nd₂Te₃ is found to be isostructural with Gd₂Te₃, crystallizing in the U₂S₃ structure type. Each of the two non-equivalent Nd atoms is surrounded by seven Te atoms, with the polyhedra best described as a seven-octahedron and a monocapped trigonal prism. All atoms lie on mirror planes.

S1. Comment

Although the structures of NdTe (Iandelli, 1955), NdTe_1.8 (Wang et al., 1966), NdTe₂ (Yarembash et al., 1965), Nd₂Te₅ (Pardo & Flahaut, 1967) and NdTe₃ (Norling & Steinfink, 1966) are known from single-crystal studies, it is surprising that the work presented here is the first single-crystal study of Nd₂Te₃. In fact, in the Ln₂Te₃ family (Ln is a rare earth) there are only two other single-crystal studies, namely Gd₂Te₃ (Swinnea et al., 1987), with the U₂S₃ structure type (Zachariasen, 1949), and Er₂Te₃ (Stöwe, 1998), with the Sc₂S₃ structure type (Dismukes & White, 1964). In the latter structure, the two independent Er atoms are octahedrally coordinated, sharing edges in the three directions of the orthorhombic structure.

Nd₂Te₃ crystallizes in the U₂S₃ structure type. In this structure (Fig. 1), there are two non-equivalent Nd atoms, each located at a site with m symmetry. Atom Nd1 is coordinated by seven Te atoms in a seven-octahedron, with Nd—Te distances in the range 3.1496 (4)–3.2287 (5) Å. These octahedra are interconnected along the b axis by the edge-sharing of two equatorial Te atoms (Te1 and Te3).

Atom Nd2 is coordinated by seven Te atoms in a monocapped trigonal prism, with Nd—Te distances in the range 3.2099 (4)–3.2732 (5) Å. There is a second capping Te2 atom at a distance of 3.6768 (5) Å, which is too long for the first coordination sphere. The height of the prism corresponds to the length of the b axis.

The Nd2Te₇ trigonal prisms share triangular faces along the b axis. For comparison, the Nd—Te distances are in the range 3.1247 (5)–3.2980 (5) Å in NdCu_0.37Te₂ (Huang et al., 2000). In Gd₂Te₃ (Swinnea et al., 1987), the Gd—Te distances are in the range 3.104 (1)–3.205 (3) Å for Gd1 and 3.169 (2)–3.240 (3) Å for Gd2.

S2. Experimental

Flat black needles of Nd₂Te₃ were obtained accidentally, in about 10% yield, in the reaction of Nd (0.0696 g; Alfa, 99.9%), Mn (0.0265 g; Alfa, 99.9%) and Te (0.1539 g; Aldrich, 99.8%) in a fused silica tube, with KBr (200 mg; Alfa, 99%) added to promote crystal growth. The materials were mixed and sealed in the tube, which was then evacuated to 10 ^-4 Torr (1 Torr = 133.322 Pa). The tube was heated to 1153 K at 0.3 K min^-1, kept at 1153 K for 4 d and cooled to 873 K at 0.04 K min^-1, and then the furnace was turned off. The reaction mixture was washed free of bromide salts with water and then dried with acetone. Semi-quantitative energy dispersive spectroscopy (EDS) verified the presence of Nd and Te in the ratio 2:3 but provided no evidence for the presence of Mn or K.

Computing details

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2000); program(s) used to refine structure: SHELXTL; molecular graphics: XP in SHELXTL.

Figures

Fig. 1. A view of the structure of Nd2Te3 along [010].

Dineodymium tritelluride

Crystal data

Nd2Te3	F(000) = 1104
Mr = 671.28	Dx = 7.028 Mg m^−3
Orthorhombic, Pnma	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2n	Cell parameters from 5792 reflections
a = 12.1856 (5) Å	θ = 2.4–29.0°
b = 4.3869 (2) Å	µ = 29.56 mm^−1
c = 11.8687 (5) Å	T = 153 K
V = 634.47 (5) Å^3	Flat needle, black
Z = 4	0.19 × 0.04 × 0.02 mm

Data collection

Bruker SMART 1000 CCD area-detector diffractometer	904 independent reflections
Radiation source: fine-focus sealed tube	886 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.037
0.3° ω scans	θmax = 29.0°, θmin = 3.3°
Absorption correction: numerical (XPREP in SHELXTL; Sheldrick, 2000)	h = −16→16
Tmin = 0.118, Tmax = 0.588	k = −5→5
7307 measured reflections	l = −15→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)] = 0.020	w = 1/[σ^2(Fo^2) + (0.02P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.046	(Δ/σ)max < 0.001
S = 1.41	Δρmax = 2.47 e Å^−3
904 reflections	Δρmin = −2.38 e Å^−3
32 parameters	Extinction correction: SHELXTL (Sheldrick, 2000), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0095 (3)

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.

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

	x	y	z	Uiso*/Ueq
Nd1	0.01532 (3)	0.2500	0.31245 (2)	0.00639 (11)
Nd2	0.19600 (2)	0.2500	0.00074 (3)	0.00673 (11)
Te1	0.11962 (3)	0.2500	0.55688 (3)	0.00653 (12)
Te2	0.27404 (3)	0.2500	0.29999 (3)	0.00711 (12)
Te3	0.45621 (3)	0.2500	0.62357 (3)	0.00612 (12)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Nd1	0.00570 (18)	0.00789 (17)	0.00559 (17)	0.000	−0.00004 (10)	0.000
Nd2	0.00525 (19)	0.00757 (17)	0.00737 (18)	0.000	0.00066 (10)	0.000
Te1	0.0058 (2)	0.00784 (19)	0.0060 (2)	0.000	0.00075 (13)	0.000
Te2	0.0053 (2)	0.00965 (19)	0.0064 (2)	0.000	0.00095 (13)	0.000
Te3	0.0057 (2)	0.00745 (19)	0.0052 (2)	0.000	−0.00039 (12)	0.000

Geometric parameters (Å, º)

Nd1—Te1^i	3.1496 (3)	Nd2—Te2	3.6769 (5)
Nd1—Te1^ii	3.1496 (3)	Te1—Nd1^ii	3.1496 (3)
Nd1—Te3^iii	3.1555 (3)	Te1—Nd1^i	3.1496 (3)
Nd1—Te3^iv	3.1555 (3)	Te1—Nd2^vi	3.2099 (4)
Nd1—Te2	3.1562 (5)	Te1—Nd2^vii	3.2099 (4)
Nd1—Te1	3.1672 (5)	Te2—Nd1^viii	3.2288 (5)
Nd1—Te2^v	3.2288 (5)	Te2—Nd2^vi	3.2590 (4)
Nd2—Te1^iv	3.2099 (4)	Te2—Nd2^vii	3.2590 (4)
Nd2—Te1^iii	3.2099 (4)	Te3—Nd1^vi	3.1555 (3)
Nd2—Te3^iii	3.2213 (4)	Te3—Nd1^vii	3.1555 (3)
Nd2—Te3^iv	3.2213 (4)	Te3—Nd2^vii	3.2213 (4)
Nd2—Te2^iii	3.2590 (4)	Te3—Nd2^vi	3.2213 (4)
Nd2—Te2^iv	3.2590 (4)	Te3—Nd2^viii	3.2733 (5)
Nd2—Te3^v	3.2733 (5)
Te1^i—Nd1—Te1^ii	88.280 (12)	Te2^iii—Nd2—Te3^v	76.731 (10)
Te1^i—Nd1—Te3^iii	85.591 (8)	Te2^iv—Nd2—Te3^v	76.731 (10)
Te1^ii—Nd1—Te3^iii	153.038 (15)	Te1^iv—Nd2—Te2	67.569 (9)
Te1^i—Nd1—Te3^iv	153.038 (15)	Te1^iii—Nd2—Te2	67.569 (9)
Te1^ii—Nd1—Te3^iv	85.591 (8)	Te3^iii—Nd2—Te2	73.248 (9)
Te3^iii—Nd1—Te3^iv	88.072 (12)	Te3^iv—Nd2—Te2	73.248 (9)
Te1^i—Nd1—Te2	122.995 (9)	Te2^iii—Nd2—Te2	132.627 (6)
Te1^ii—Nd1—Te2	122.995 (9)	Te2^iv—Nd2—Te2	132.627 (6)
Te3^iii—Nd1—Te2	81.772 (11)	Te3^v—Nd2—Te2	131.781 (12)
Te3^iv—Nd1—Te2	81.772 (11)	Nd1^ii—Te1—Nd1^i	88.280 (12)
Te1^i—Nd1—Te1	76.025 (10)	Nd1^ii—Te1—Nd1	103.975 (10)
Te1^ii—Nd1—Te1	76.025 (10)	Nd1^i—Te1—Nd1	103.975 (10)
Te3^iii—Nd1—Te1	127.344 (9)	Nd1^ii—Te1—Nd2^vi	89.527 (7)
Te3^iv—Nd1—Te1	127.344 (9)	Nd1^i—Te1—Nd2^vi	160.654 (14)
Te2—Nd1—Te1	69.026 (11)	Nd1—Te1—Nd2^vi	95.208 (11)
Te1^i—Nd1—Te2^v	74.225 (10)	Nd1^ii—Te1—Nd2^vii	160.654 (14)
Te1^ii—Nd1—Te2^v	74.225 (10)	Nd1^i—Te1—Nd2^vii	89.527 (7)
Te3^iii—Nd1—Te2^v	78.841 (10)	Nd1—Te1—Nd2^vii	95.208 (11)
Te3^iv—Nd1—Te2^v	78.841 (10)	Nd2^vi—Te1—Nd2^vii	86.211 (12)
Te2—Nd1—Te2^v	152.899 (11)	Nd1—Te2—Nd1^viii	158.271 (13)
Te1—Nd1—Te2^v	138.075 (14)	Nd1—Te2—Nd2^vi	94.453 (11)
Te1^iv—Nd2—Te1^iii	86.211 (12)	Nd1^viii—Te2—Nd2^vi	101.548 (11)
Te1^iv—Nd2—Te3^iii	140.750 (13)	Nd1—Te2—Nd2^vii	94.453 (11)
Te1^iii—Nd2—Te3^iii	81.012 (8)	Nd1^viii—Te2—Nd2^vii	101.548 (11)
Te1^iv—Nd2—Te3^iv	81.012 (8)	Nd2^vi—Te2—Nd2^vii	84.604 (12)
Te1^iii—Nd2—Te3^iv	140.750 (13)	Nd1—Te2—Nd2	77.696 (10)
Te3^iii—Nd2—Te3^iv	85.832 (12)	Nd1^viii—Te2—Nd2	80.576 (11)
Te1^iv—Nd2—Te2^iii	122.227 (13)	Nd2^vi—Te2—Nd2	137.322 (6)
Te1^iii—Nd2—Te2^iii	67.259 (9)	Nd2^vii—Te2—Nd2	137.322 (6)
Te3^iii—Nd2—Te2^iii	86.392 (8)	Nd1^vi—Te3—Nd1^vii	88.072 (12)
Te3^iv—Nd2—Te2^iii	148.610 (14)	Nd1^vi—Te3—Nd2^vii	149.109 (15)
Te1^iv—Nd2—Te2^iv	67.259 (9)	Nd1^vii—Te3—Nd2^vii	84.923 (7)
Te1^iii—Nd2—Te2^iv	122.227 (13)	Nd1^vi—Te3—Nd2^vi	84.923 (7)
Te3^iii—Nd2—Te2^iv	148.610 (14)	Nd1^vii—Te3—Nd2^vi	149.109 (15)
Te3^iv—Nd2—Te2^iv	86.392 (8)	Nd2^vii—Te3—Nd2^vi	85.832 (12)
Te2^iii—Nd2—Te2^iv	84.604 (12)	Nd1^vi—Te3—Nd2^viii	102.831 (11)
Te1^iv—Nd2—Te3^v	135.922 (7)	Nd1^vii—Te3—Nd2^viii	102.831 (11)
Te1^iii—Nd2—Te3^v	135.922 (7)	Nd2^vii—Te3—Nd2^viii	108.059 (10)
Te3^iii—Nd2—Te3^v	71.941 (10)	Nd2^vi—Te3—Nd2^viii	108.059 (10)
Te3^iv—Nd2—Te3^v	71.941 (10)

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