Titanium germanium anti­monide, TiGeSb

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, P 4/n m m

• 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[F² > 2σ(F²)] = 0.032

• wR(F²) = 0.081

• S = 1.17

• 181 reflections

• 10 parameters

• Δρ_max = 1.95 e Å⁻³

• Δρ_min = −2.53 e Å⁻³

Table 1
Selected bond lengths (Å)

Ti—Ge	2.7570 (10)
Ti—Sb^i	2.8452 (7)
Ti—Sb	3.0129 (14)
Ge—Ge^ii	2.6179 (4)
Symmetry codes: (i) -x, -y, -z+1; (ii) -x+1, -y, -z.

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.

Supporting information

S1. 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).

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).

S2. 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.

S3. 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.

Computing details

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

Figures

Fig. 1. Projection of the TiGeSb structure approximately along the a axis. Displacement ellipsoids are drawn at the 90% probability level.

titanium germanium antimonide

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) Å^3	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 monochromator	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 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)] = 0.032	w = 1/[σ^2(Fo^2) + (0.044P)^2 + 0.3679P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 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+0.001xFc^2λ^3/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)

	U^11	U^22	U^33	U^12	U^13	U^23
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, º)

Ti—Ge^i	2.7570 (10)	Ge—Ge^ix	2.6179 (3)
Ti—Ge^ii	2.7570 (10)	Ge—Ti^i	2.7570 (10)
Ti—Ge^iii	2.7570 (10)	Ge—Ti^x	2.7570 (10)
Ti—Ge	2.7570 (10)	Ge—Ti^iii	2.7570 (10)
Ti—Sb^iv	2.8452 (7)	Sb—Ti^iv	2.8452 (7)
Ti—Sb^v	2.8452 (7)	Sb—Ti^v	2.8452 (7)
Ti—Sb^vi	2.8452 (7)	Sb—Ti^vi	2.8452 (7)
Ti—Sb^vii	2.8452 (7)	Sb—Ti^vii	2.8452 (7)
Ti—Sb	3.0129 (14)	Sb—Sb^v	3.2337 (7)
Ge—Ge^viii	2.6179 (4)	Sb—Sb^iv	3.2337 (7)
Ge—Ge^i	2.6179 (4)	Sb—Sb^vii	3.2337 (7)
Ge—Ge^iii	2.6179 (4)	Sb—Sb^vi	3.2337 (7)
Ge^i—Ti—Ge^ii	56.69 (2)	Ti^i—Ge—Ti^x	123.31 (2)
Ge^i—Ti—Ge^iii	84.35 (4)	Ge^viii—Ge—Ti	118.344 (11)
Ge^ii—Ti—Ge^iii	56.69 (2)	Ge^i—Ge—Ti	61.656 (11)
Ge^i—Ti—Ge	56.69 (2)	Ge^iii—Ge—Ti	61.656 (11)
Ge^ii—Ti—Ge	84.35 (4)	Ge^ix—Ge—Ti	118.344 (11)
Ge^iii—Ti—Ge	56.69 (2)	Ti^i—Ge—Ti	123.31 (2)
Ge^i—Ti—Sb^iv	136.65 (2)	Ti^x—Ge—Ti	84.35 (4)
Ge^ii—Ti—Sb^iv	136.65 (2)	Ge^viii—Ge—Ti^iii	61.656 (11)
Ge^iii—Ti—Sb^iv	81.574 (14)	Ge^i—Ge—Ti^iii	118.344 (11)
Ge—Ti—Sb^iv	81.574 (14)	Ge^iii—Ge—Ti^iii	61.656 (11)
Ge^i—Ti—Sb^v	81.574 (14)	Ge^ix—Ge—Ti^iii	118.344 (11)
Ge^ii—Ti—Sb^v	81.574 (14)	Ti^i—Ge—Ti^iii	84.35 (4)
Ge^iii—Ti—Sb^v	136.65 (2)	Ti^x—Ge—Ti^iii	123.31 (2)
Ge—Ti—Sb^v	136.65 (2)	Ti—Ge—Ti^iii	123.31 (2)
Sb^iv—Ti—Sb^v	133.88 (5)	Ti^iv—Sb—Ti^v	133.88 (5)
Ge^i—Ti—Sb^vi	136.65 (2)	Ti^iv—Sb—Ti^vi	81.17 (2)
Ge^ii—Ti—Sb^vi	81.574 (14)	Ti^v—Sb—Ti^vi	81.17 (2)
Ge^iii—Ti—Sb^vi	81.574 (14)	Ti^iv—Sb—Ti^vii	81.17 (2)
Ge—Ti—Sb^vi	136.65 (2)	Ti^v—Sb—Ti^vii	81.17 (2)
Sb^iv—Ti—Sb^vi	81.17 (2)	Ti^vi—Sb—Ti^vii	133.88 (5)
Sb^v—Ti—Sb^vi	81.17 (2)	Ti^iv—Sb—Ti	113.06 (3)
Ge^i—Ti—Sb^vii	81.574 (14)	Ti^v—Sb—Ti	113.06 (3)
Ge^ii—Ti—Sb^vii	136.65 (2)	Ti^vi—Sb—Ti	113.06 (3)
Ge^iii—Ti—Sb^vii	136.65 (2)	Ti^vii—Sb—Ti	113.06 (3)
Ge—Ti—Sb^vii	81.574 (14)	Ti^iv—Sb—Sb^v	167.11 (4)
Sb^iv—Ti—Sb^vii	81.17 (2)	Ti^v—Sb—Sb^v	59.01 (3)
Sb^v—Ti—Sb^vii	81.17 (2)	Ti^vi—Sb—Sb^v	103.295 (14)
Sb^vi—Ti—Sb^vii	133.88 (5)	Ti^vii—Sb—Sb^v	103.295 (14)
Ge^i—Ti—Sb	137.823 (19)	Ti—Sb—Sb^v	54.051 (16)
Ge^ii—Ti—Sb	137.823 (19)	Ti^iv—Sb—Sb^iv	59.01 (3)
Ge^iii—Ti—Sb	137.823 (19)	Ti^v—Sb—Sb^iv	167.11 (4)
Ge—Ti—Sb	137.823 (19)	Ti^vi—Sb—Sb^iv	103.295 (14)
Sb^iv—Ti—Sb	66.94 (3)	Ti^vii—Sb—Sb^iv	103.295 (14)
Sb^v—Ti—Sb	66.94 (3)	Ti—Sb—Sb^iv	54.051 (16)
Sb^vi—Ti—Sb	66.94 (3)	Sb^v—Sb—Sb^iv	108.10 (3)
Sb^vii—Ti—Sb	66.94 (3)	Ti^iv—Sb—Sb^vii	103.295 (14)
Ge^viii—Ge—Ge^i	180.0	Ti^v—Sb—Sb^vii	103.295 (14)
Ge^viii—Ge—Ge^iii	90.0	Ti^vi—Sb—Sb^vii	167.11 (4)
Ge^i—Ge—Ge^iii	90.0	Ti^vii—Sb—Sb^vii	59.01 (3)
Ge^viii—Ge—Ge^ix	90.0	Ti—Sb—Sb^vii	54.051 (16)
Ge^i—Ge—Ge^ix	90.0	Sb^v—Sb—Sb^vii	69.840 (16)
Ge^iii—Ge—Ge^ix	180.0	Sb^iv—Sb—Sb^vii	69.840 (16)
Ge^viii—Ge—Ti^i	118.344 (11)	Ti^iv—Sb—Sb^vi	103.295 (14)
Ge^i—Ge—Ti^i	61.656 (11)	Ti^v—Sb—Sb^vi	103.295 (14)
Ge^iii—Ge—Ti^i	118.344 (11)	Ti^vi—Sb—Sb^vi	59.01 (3)
Ge^ix—Ge—Ti^i	61.656 (11)	Ti^vii—Sb—Sb^vi	167.11 (4)
Ge^viii—Ge—Ti^x	61.656 (11)	Ti—Sb—Sb^vi	54.051 (16)
Ge^i—Ge—Ti^x	118.344 (11)	Sb^v—Sb—Sb^vi	69.840 (16)
Ge^iii—Ge—Ti^x	118.344 (11)	Sb^iv—Sb—Sb^vi	69.840 (16)
Ge^ix—Ge—Ti^x	61.656 (11)	Sb^vii—Sb—Sb^vi	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.