Titanium germanium anti­monide, TiGeSb

Abstract

TiGeSb adopts the PbFCl- or ZrSiS-type structure, with Ti atoms (4mm symmetry) centred within monocapped square anti­prisms generated by the stacking of denser square nets of Ge atoms ( m2 symmetry) alternating with less dense square nets of Sb atoms (4mm symmetry).

Related literature

For PbFCl- or ZrSiS-type structures, see: Tremel & Hoffmann (1987 ▶). For a previous report on TiGeSb, see: Dashjav & Kleinke (2002 ▶). The Ti—Ge—Sb phase diagram at 670 K was reported by Kozlov & Pavlyuk (2004 ▶). For the related ZrGeSb, see: Lam & Mar (1997 ▶). For background to solid solutions in this class of compounds, see: Soheilnia et al. (2003 ▶); Kozlov & Pavlyuk (2004 ▶). Metallic radii were taken from Pauling (1960 ▶).

Experimental

Crystal data

• TiGeSb

• M _r = 242.24

• Tetragonal,

• a = 3.7022 (5) Å

• c = 8.2137 (12) Å

• V = 112.58 (3) ų

• Z = 2

• Mo Kα radiation

• μ = 28.18 mm⁻¹

• T = 295 K

• 0.12 × 0.11 × 0.01 mm

Data collection

• Enraf–Nonius CAD-4 diffractometer

• Absorption correction: numerical (SHELXTL; Sheldrick, 2008 ▶) T _min = 0.117, T _max = 0.718

• 1906 measured reflections

• 181 independent reflections

• 178 reflections with I > 2σ(I)

• R _int = 0.125

• 3 standard reflections frequency: 120 min intensity decay: none

Refinement

• R[F ² > 2σ(F ²)] = 0.032

• wR(F ²) = 0.081

• S = 1.17

• 181 reflections

• 10 parameters

• Δρ_max = 1.95 e Å⁻³

• Δρ_min = −2.53 e Å⁻³

Data collection: CAD-4-PC (Enraf–Nonius, 1993 ▶); cell refinement: CAD-4-PC; data reduction: XCAD4 (Harms & Wocadlo, 1995 ▶); program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: ATOMS (Dowty, 1999 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

Ti—Ge	2.7570 (10)
Ti—Sbi	2.8452 (7)
Ti—Sb	3.0129 (14)
Ge—Geii	2.6179 (4)

Symmetry codes: (i) ; (ii) .

supplementary crystallographic information

Comment

After a report of the ternary antimonide ZrGeSb (Lam & Mar, 1997), the corresponding Ti and Hf analogues were later described in a conference proceeding, but full crystallographic details have not been forthcoming (Dashjav & Kleinke, 2002). The complete structure of TiGeSb, which is absent in the Ti—Ge—Sb phase diagram at 670 K (Kozlov & Pavlyuk, 2004) but was prepared here at 1273 K, is presented. Common to many equiatomic compounds of the formulation MAB (M = large transition-metal atom; A, B = main group atoms), TiGeSb adopts the PbFCl- or ZrSiS-type structure, among other names (Tremel & Hoffmann, 1987). Square nets of each type of atom, with the Ge net being twice as dense as the other two, are stacked along the c axis (Fig. 1). The Zr atoms are nine-coordinate, centred within monocapped square antiprisms. The Ge–Ge distances are 0.13 Å longer than the sum of the Pauling metallic radii (2.48 Å; Pauling, 1960), indicative of weak polyanionic bonding. The solid solutions ZrGe_xSb_1-x and HfGe_xSb_1-x (up to x = 0.2) form related orthorhombic PbCl₂-type structures (Soheilnia et al., 2003), whereas TiGe_xSb_1-x adopts a NiAs-type structure (Kozlov & Pavlyuk, 2004).

Experimental

A 0.25 g mixture of Ti (99.98%, Cerac), Ge (99.999%, Cerac), and Sb (99.995%, Aldrich) powders in a 1:1:3 molar ratio was placed in an evacuated fused-silica tube. The tube was heated at 873 K for 2 d and 1273 K for 2 d. Silver plate-shaped crystals were obtained, which were found by semiquantitative energy-dispersive X-ray (EDX) analysis to have a composition (at%) of 32 (2)% Ti, 35 (2)% Ge, and 33 (2)% Sb, in good agreement with the formula TiGeSb.

Refinement

Analysis of Weissenberg photographs on a plate-shaped crystal, subsequently transferred to the four-circle diffractometer, established Laue symmetry 4/mmm and provided approximate cell parameters of a = 3.71 Å and c = 8.22 Å. In the final Fourier map based on origin choice 2 of space group P4/nmm the maximum peak and deepest hole are located 0.67 Å and 0.02 Å, respectively, from the Sb atom.

Figures

Fig. 1.

Projection of the TiGeSb structure approximately along the a axis. Displacement ellipsoids are drawn at the 90% probability level.

Crystal data

TiGeSb	Dx = 7.146 Mg m−3
Mr = 242.24	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P4/nmm	Cell parameters from 24 reflections
Hall symbol: -P 4a 2a	θ = 11.0–23.3°
a = 3.7022 (5) Å	µ = 28.18 mm−1
c = 8.2137 (12) Å	T = 295 K
V = 112.58 (3) Å3	Plate, silver
Z = 2	0.12 × 0.11 × 0.01 mm
F(000) = 210

Data collection

Enraf–Nonius CAD-4 diffractometer	178 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.125
graphite	θmax = 34.8°, θmin = 2.5°
θ/2θ scans	h = −5→5
Absorption correction: numerical (SHELXTL; Sheldrick, 2008)	k = −5→5
Tmin = 0.117, Tmax = 0.718	l = −13→13
1906 measured reflections	3 standard reflections every 120 min
181 independent reflections	intensity decay: none

Refinement

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.032	w = 1/[σ2(Fo2) + (0.044P)2 + 0.3679P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.081	(Δ/σ)max < 0.001
S = 1.17	Δρmax = 1.95 e Å−3
181 reflections	Δρmin = −2.53 e Å−3
10 parameters	Extinction correction: SHELXTL (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraints	Extinction coefficient: 0.038 (9)

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
Ti	0.2500	0.2500	0.24875 (16)	0.0054 (3)
Ge	0.7500	0.2500	0.0000	0.0063 (3)
Sb	0.2500	0.2500	0.61556 (6)	0.0063 (3)

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Ti	0.0060 (4)	0.0060 (4)	0.0043 (6)	0.000	0.000	0.000
Ge	0.0065 (4)	0.0065 (4)	0.0059 (4)	0.000	0.000	0.000
Sb	0.0056 (3)	0.0056 (3)	0.0076 (4)	0.000	0.000	0.000

Geometric parameters (Å, °)

Ti—Gei	2.7570 (10)	Ge—Geix	2.6179 (3)
Ti—Geii	2.7570 (10)	Ge—Tii	2.7570 (10)
Ti—Geiii	2.7570 (10)	Ge—Tix	2.7570 (10)
Ti—Ge	2.7570 (10)	Ge—Tiiii	2.7570 (10)
Ti—Sbiv	2.8452 (7)	Sb—Tiiv	2.8452 (7)
Ti—Sbv	2.8452 (7)	Sb—Tiv	2.8452 (7)
Ti—Sbvi	2.8452 (7)	Sb—Tivi	2.8452 (7)
Ti—Sbvii	2.8452 (7)	Sb—Tivii	2.8452 (7)
Ti—Sb	3.0129 (14)	Sb—Sbv	3.2337 (7)
Ge—Geviii	2.6179 (4)	Sb—Sbiv	3.2337 (7)
Ge—Gei	2.6179 (4)	Sb—Sbvii	3.2337 (7)
Ge—Geiii	2.6179 (4)	Sb—Sbvi	3.2337 (7)
Gei—Ti—Geii	56.69 (2)	Tii—Ge—Tix	123.31 (2)
Gei—Ti—Geiii	84.35 (4)	Geviii—Ge—Ti	118.344 (11)
Geii—Ti—Geiii	56.69 (2)	Gei—Ge—Ti	61.656 (11)
Gei—Ti—Ge	56.69 (2)	Geiii—Ge—Ti	61.656 (11)
Geii—Ti—Ge	84.35 (4)	Geix—Ge—Ti	118.344 (11)
Geiii—Ti—Ge	56.69 (2)	Tii—Ge—Ti	123.31 (2)
Gei—Ti—Sbiv	136.65 (2)	Tix—Ge—Ti	84.35 (4)
Geii—Ti—Sbiv	136.65 (2)	Geviii—Ge—Tiiii	61.656 (11)
Geiii—Ti—Sbiv	81.574 (14)	Gei—Ge—Tiiii	118.344 (11)
Ge—Ti—Sbiv	81.574 (14)	Geiii—Ge—Tiiii	61.656 (11)
Gei—Ti—Sbv	81.574 (14)	Geix—Ge—Tiiii	118.344 (11)
Geii—Ti—Sbv	81.574 (14)	Tii—Ge—Tiiii	84.35 (4)
Geiii—Ti—Sbv	136.65 (2)	Tix—Ge—Tiiii	123.31 (2)
Ge—Ti—Sbv	136.65 (2)	Ti—Ge—Tiiii	123.31 (2)
Sbiv—Ti—Sbv	133.88 (5)	Tiiv—Sb—Tiv	133.88 (5)
Gei—Ti—Sbvi	136.65 (2)	Tiiv—Sb—Tivi	81.17 (2)
Geii—Ti—Sbvi	81.574 (14)	Tiv—Sb—Tivi	81.17 (2)
Geiii—Ti—Sbvi	81.574 (14)	Tiiv—Sb—Tivii	81.17 (2)
Ge—Ti—Sbvi	136.65 (2)	Tiv—Sb—Tivii	81.17 (2)
Sbiv—Ti—Sbvi	81.17 (2)	Tivi—Sb—Tivii	133.88 (5)
Sbv—Ti—Sbvi	81.17 (2)	Tiiv—Sb—Ti	113.06 (3)
Gei—Ti—Sbvii	81.574 (14)	Tiv—Sb—Ti	113.06 (3)
Geii—Ti—Sbvii	136.65 (2)	Tivi—Sb—Ti	113.06 (3)
Geiii—Ti—Sbvii	136.65 (2)	Tivii—Sb—Ti	113.06 (3)
Ge—Ti—Sbvii	81.574 (14)	Tiiv—Sb—Sbv	167.11 (4)
Sbiv—Ti—Sbvii	81.17 (2)	Tiv—Sb—Sbv	59.01 (3)
Sbv—Ti—Sbvii	81.17 (2)	Tivi—Sb—Sbv	103.295 (14)
Sbvi—Ti—Sbvii	133.88 (5)	Tivii—Sb—Sbv	103.295 (14)
Gei—Ti—Sb	137.823 (19)	Ti—Sb—Sbv	54.051 (16)
Geii—Ti—Sb	137.823 (19)	Tiiv—Sb—Sbiv	59.01 (3)
Geiii—Ti—Sb	137.823 (19)	Tiv—Sb—Sbiv	167.11 (4)
Ge—Ti—Sb	137.823 (19)	Tivi—Sb—Sbiv	103.295 (14)
Sbiv—Ti—Sb	66.94 (3)	Tivii—Sb—Sbiv	103.295 (14)
Sbv—Ti—Sb	66.94 (3)	Ti—Sb—Sbiv	54.051 (16)
Sbvi—Ti—Sb	66.94 (3)	Sbv—Sb—Sbiv	108.10 (3)
Sbvii—Ti—Sb	66.94 (3)	Tiiv—Sb—Sbvii	103.295 (14)
Geviii—Ge—Gei	180.0	Tiv—Sb—Sbvii	103.295 (14)
Geviii—Ge—Geiii	90.0	Tivi—Sb—Sbvii	167.11 (4)
Gei—Ge—Geiii	90.0	Tivii—Sb—Sbvii	59.01 (3)
Geviii—Ge—Geix	90.0	Ti—Sb—Sbvii	54.051 (16)
Gei—Ge—Geix	90.0	Sbv—Sb—Sbvii	69.840 (16)
Geiii—Ge—Geix	180.0	Sbiv—Sb—Sbvii	69.840 (16)
Geviii—Ge—Tii	118.344 (11)	Tiiv—Sb—Sbvi	103.295 (14)
Gei—Ge—Tii	61.656 (11)	Tiv—Sb—Sbvi	103.295 (14)
Geiii—Ge—Tii	118.344 (11)	Tivi—Sb—Sbvi	59.01 (3)
Geix—Ge—Tii	61.656 (11)	Tivii—Sb—Sbvi	167.11 (4)
Geviii—Ge—Tix	61.656 (11)	Ti—Sb—Sbvi	54.051 (16)
Gei—Ge—Tix	118.344 (11)	Sbv—Sb—Sbvi	69.840 (16)
Geiii—Ge—Tix	118.344 (11)	Sbiv—Sb—Sbvi	69.840 (16)
Geix—Ge—Tix	61.656 (11)	Sbvii—Sb—Sbvi	108.10 (3)

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