YbAgxSi2−x [x = 0.28 (1)] with the tetragonal α-ThSi2 structure type

Bobev, S.; Bauer, E.D.

doi:10.1107/S1600536805013103

YbAg_xSi_2−x [x = 0.28 (1)] with the tetragonal α-ThSi₂ structure type

Single crystals of the title compound, ytterbium silver silicide, were synthesized from the corresponding elements using a eutectic Ag/Si mixture as a solvent. Structure determination suggested the composition of the product to be YbAg_xSi_2−x [x = 0.28 (1)], i.e. a new ternary derivative of the α-ThSi₂ structure type, which crystallizes in the body-centered tetragonal space group I4₁/amd. The two atoms in the asymmetric unit lie on special positions with Wyckoff symbols 4a (Yb), and 8e (disordered Ag and Si).

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536805013103/wm6066sup1.cif Contains datablocks I, global
	Structure factor file (CIF format) https://doi.org/10.1107/S1600536805013103/wm6066Isup2.hkl Contains datablock I

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Key indicators

Single-crystal X-ray study
T = 293 K
Mean (Please check) = 0.000 Å
R factor = 0.009
wR factor = 0.020
Data-to-parameter ratio = 13.1

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT041_ALERT_1_C Calc. and Rep. SumFormula Strings    Differ ....          ?
PLAT045_ALERT_1_C Calculated and Reported Z Differ by ............       0.25 Ratio
PLAT068_ALERT_1_C Reported F000 Differs from Calcd (or Missing)...          ?
PLAT077_ALERT_4_C Unitcell contains non-integer number of atoms ..          ?
PLAT301_ALERT_3_C Main Residue  Disorder .........................      10.00 Perc.

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   5 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   3 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion

Computing details top

Data collection: SMART (Bruker, 2002); cell refinement: SMART; data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXTL (Sheldrick, 2001); program(s) used to refine structure: SHELXTL; molecular graphics: XP in SHELXTL; software used to prepare material for publication: SHELXTL.

ytterbium silver silicide top

Crystal data top

YbAg_.28Si_1.72	D_x = 7.091 Mg m⁻³
M_r = 251.76	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, I4₁/amd	Cell parameters from 796 reflections
Hall symbol: -I 4bd 2	θ = 5.2–30.9°
a = 4.0757 (2) Å	µ = 42.37 mm⁻¹
c = 14.1965 (11) Å	T = 293 K
V = 235.82 (2) Å³	Bar, grey
Z = 4	0.05 × 0.04 × 0.03 mm
F(000) = 429

Data collection top

Bruker APEX SMART diffractometer	118 independent reflections
Radiation source: fine-focus sealed tube	107 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.018
Detector resolution: 8.3 pixels mm^-1	θ_max = 30.9°, θ_min = 5.2°
ω scans	h = −5→5
Absorption correction: multi-scan (SADABS; Sheldrick, 2003)	k = −5→4
T_min = 0.155, T_max = 0.280	l = −20→19
796 measured reflections

Refinement top

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)] = 0.009	w = 1/[σ²(F_o²) + (0.0097P)² + 0.0681P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.020	(Δ/σ)_max < 0.001
S = 1.23	Δρ_max = 0.45 e Å⁻³
118 reflections	Δρ_min = −0.66 e Å⁻³
9 parameters	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0086 (6)

Special details top

Experimental. Data collection was performed with four batch runs at φ = 0.00 ° (606 frames), at φ = 90.00 ° (606 frames), at φ = 180.00 ° (606 frames), and at φ = 270.00 (606 frames). Frame width = 0.30 \& in ω. Data was merged, corrected for decay, and treated with multi-scan absorption corrections. Structure was solved readily using direct methods and refined on F² using the SHELXL package (Sheldrick, 2001).

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 (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Yb	0.0000	0.7500	0.1250	0.00700 (14)
Si	0.0000	0.2500	0.29237 (6)	0.0077 (4)	0.858 (4)
Ag	0.0000	0.2500	0.29237 (6)	0.0077 (4)	0.142 (4)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Yb	0.00575 (15)	0.00575 (15)	0.00951 (17)	0.000	0.000	0.000
Si	0.0044 (5)	0.0145 (6)	0.0041 (4)	0.000	0.000	0.000
Ag	0.0044 (5)	0.0145 (6)	0.0041 (4)	0.000	0.000	0.000

Geometric parameters (Å, º) top

Yb—Agⁱ	3.1116 (3)	Si—Ag^ix	2.3463 (16)
Yb—Agⁱⁱ	3.1116 (3)	Si—Si^ix	2.3463 (16)
Yb—Siⁱ	3.1116 (3)	Si—Ag^iv	2.3664 (8)
Yb—Siⁱⁱ	3.1116 (3)	Si—Si^iv	2.3664 (8)
Yb—Agⁱⁱⁱ	3.1116 (3)	Si—Ag^viii	2.3664 (8)
Yb—Ag^iv	3.1116 (3)	Si—Si^viii	2.3664 (8)
Yb—Siⁱⁱⁱ	3.1116 (3)	Si—Ybⁱⁱ	3.1116 (3)
Yb—Si^iv	3.1116 (3)	Si—Yb^iv	3.1116 (3)
Yb—Ag^v	3.1116 (3)	Si—Yb^vii	3.1116 (3)
Yb—Ag^vi	3.1116 (3)	Si—Yb^viii	3.1116 (3)
Yb—Ag^vii	3.1116 (3)	Si—Yb^x	3.1302 (6)
Yb—Ag^viii	3.1116 (3)

Agⁱ—Yb—Agⁱⁱ	180.00 (3)	Ag^vi—Yb—Ag^viii	44.30 (3)
Agⁱ—Yb—Siⁱ	0.00 (3)	Ag^vii—Yb—Ag^viii	135.70 (3)
Agⁱⁱ—Yb—Siⁱ	180.0	Ag^ix—Si—Ag^iv	120.55 (3)
Agⁱ—Yb—Siⁱⁱ	180.00 (3)	Si^ix—Si—Ag^iv	120.55 (3)
Agⁱⁱ—Yb—Siⁱⁱ	0.00 (3)	Si^ix—Si—Si^iv	120.55 (3)
Siⁱ—Yb—Siⁱⁱ	180.00 (3)	Ag^ix—Si—Ag^viii	120.55 (3)
Agⁱ—Yb—Agⁱⁱⁱ	135.70 (3)	Si^ix—Si—Ag^viii	120.55 (3)
Agⁱⁱ—Yb—Agⁱⁱⁱ	44.30 (3)	Ag^iv—Si—Ag^viii	118.90 (7)
Siⁱ—Yb—Agⁱⁱⁱ	135.70 (3)	Si^iv—Si—Ag^viii	118.90 (7)
Siⁱⁱ—Yb—Agⁱⁱⁱ	44.30 (3)	Ag^ix—Si—Si^viii	120.55 (3)
Agⁱ—Yb—Ag^iv	44.30 (3)	Si^ix—Si—Si^viii	120.55 (3)
Agⁱⁱ—Yb—Ag^iv	135.70 (3)	Ag^iv—Si—Si^viii	118.90 (7)
Siⁱ—Yb—Ag^iv	44.30 (3)	Si^iv—Si—Si^viii	118.90 (7)
Siⁱⁱ—Yb—Ag^iv	135.70 (3)	Ag^ix—Si—Ybⁱⁱ	67.851 (14)
Agⁱⁱⁱ—Yb—Ag^iv	180.0	Si^ix—Si—Ybⁱⁱ	67.851 (14)
Agⁱ—Yb—Siⁱⁱⁱ	135.70 (3)	Ag^iv—Si—Ybⁱⁱ	139.082 (6)
Agⁱⁱ—Yb—Siⁱⁱⁱ	44.30 (3)	Si^iv—Si—Ybⁱⁱ	139.082 (6)
Siⁱ—Yb—Siⁱⁱⁱ	135.70 (3)	Ag^viii—Si—Ybⁱⁱ	68.139 (14)
Siⁱⁱ—Yb—Siⁱⁱⁱ	44.30 (3)	Si^viii—Si—Ybⁱⁱ	68.139 (14)
Agⁱⁱⁱ—Yb—Siⁱⁱⁱ	0.00 (3)	Ag^ix—Si—Yb^iv	67.851 (14)
Ag^iv—Yb—Siⁱⁱⁱ	180.0	Si^ix—Si—Yb^iv	67.851 (14)
Agⁱ—Yb—Si^iv	44.30 (3)	Ag^iv—Si—Yb^iv	68.139 (14)
Agⁱⁱ—Yb—Si^iv	135.70 (3)	Si^iv—Si—Yb^iv	68.139 (14)
Siⁱ—Yb—Si^iv	44.30 (3)	Ag^viii—Si—Yb^iv	139.082 (6)
Siⁱⁱ—Yb—Si^iv	135.70 (3)	Si^viii—Si—Yb^iv	139.082 (6)
Agⁱⁱⁱ—Yb—Si^iv	180.0	Ybⁱⁱ—Si—Yb^iv	135.70 (3)
Ag^iv—Yb—Si^iv	0.0	Ag^ix—Si—Yb^vii	67.851 (14)
Siⁱⁱⁱ—Yb—Si^iv	180.0	Si^ix—Si—Yb^vii	67.851 (14)
Agⁱ—Yb—Ag^v	81.828 (10)	Ag^iv—Si—Yb^vii	68.139 (14)
Agⁱⁱ—Yb—Ag^v	98.172 (10)	Si^iv—Si—Yb^vii	68.139 (14)
Siⁱ—Yb—Ag^v	81.828 (10)	Ag^viii—Si—Yb^vii	139.082 (6)
Siⁱⁱ—Yb—Ag^v	98.172 (10)	Si^viii—Si—Yb^vii	139.082 (6)
Agⁱⁱⁱ—Yb—Ag^v	81.828 (10)	Ybⁱⁱ—Si—Yb^vii	81.828 (10)
Ag^iv—Yb—Ag^v	98.172 (10)	Yb^iv—Si—Yb^vii	81.828 (10)
Siⁱⁱⁱ—Yb—Ag^v	81.828 (10)	Ag^ix—Si—Yb^viii	67.851 (14)
Si^iv—Yb—Ag^v	98.172 (10)	Si^ix—Si—Yb^viii	67.851 (14)
Agⁱ—Yb—Ag^vi	81.828 (10)	Ag^iv—Si—Yb^viii	139.082 (6)
Agⁱⁱ—Yb—Ag^vi	98.172 (10)	Si^iv—Si—Yb^viii	139.082 (6)
Siⁱ—Yb—Ag^vi	81.828 (10)	Ag^viii—Si—Yb^viii	68.139 (14)
Siⁱⁱ—Yb—Ag^vi	98.172 (10)	Si^viii—Si—Yb^viii	68.139 (14)
Agⁱⁱⁱ—Yb—Ag^vi	81.828 (10)	Ybⁱⁱ—Si—Yb^viii	81.828 (10)
Ag^iv—Yb—Ag^vi	98.172 (10)	Yb^iv—Si—Yb^viii	81.828 (10)
Siⁱⁱⁱ—Yb—Ag^vi	81.828 (10)	Yb^vii—Si—Yb^viii	135.70 (3)
Si^iv—Yb—Ag^vi	98.172 (10)	Ag^ix—Si—Yb^x	139.381 (10)
Ag^v—Yb—Ag^vi	135.70 (3)	Si^ix—Si—Yb^x	139.381 (10)
Agⁱ—Yb—Ag^vii	98.172 (10)	Ag^iv—Si—Yb^x	67.30 (3)
Agⁱⁱ—Yb—Ag^vii	81.828 (10)	Si^iv—Si—Yb^x	67.30 (3)
Siⁱ—Yb—Ag^vii	98.172 (10)	Ag^viii—Si—Yb^x	67.30 (3)
Siⁱⁱ—Yb—Ag^vii	81.828 (10)	Si^viii—Si—Yb^x	67.30 (3)
Agⁱⁱⁱ—Yb—Ag^vii	98.172 (10)	Ybⁱⁱ—Si—Yb^x	135.443 (14)
Ag^iv—Yb—Ag^vii	81.828 (10)	Yb^iv—Si—Yb^x	81.941 (6)
Siⁱⁱⁱ—Yb—Ag^vii	98.172 (10)	Yb^vii—Si—Yb^x	135.443 (14)
Si^iv—Yb—Ag^vii	81.828 (10)	Yb^viii—Si—Yb^x	81.941 (6)
Ag^v—Yb—Ag^vii	44.30 (3)	Ag^ix—Si—Yb	139.381 (10)
Ag^vi—Yb—Ag^vii	180.0	Si^ix—Si—Yb	139.381 (10)
Agⁱ—Yb—Ag^viii	98.172 (10)	Ag^iv—Si—Yb	67.30 (3)
Agⁱⁱ—Yb—Ag^viii	81.828 (10)	Si^iv—Si—Yb	67.30 (3)
Siⁱ—Yb—Ag^viii	98.172 (10)	Ag^viii—Si—Yb	67.30 (3)
Siⁱⁱ—Yb—Ag^viii	81.828 (10)	Si^viii—Si—Yb	67.30 (3)
Agⁱⁱⁱ—Yb—Ag^viii	98.172 (10)	Ybⁱⁱ—Si—Yb	81.941 (6)
Ag^iv—Yb—Ag^viii	81.828 (10)	Yb^iv—Si—Yb	135.443 (14)
Siⁱⁱⁱ—Yb—Ag^viii	98.172 (10)	Yb^vii—Si—Yb	81.941 (6)
Si^iv—Yb—Ag^viii	81.828 (10)	Yb^viii—Si—Yb	135.443 (14)
Ag^v—Yb—Ag^viii	180.00 (3)	Yb^x—Si—Yb	81.24 (2)

Symmetry codes: (i) −y−1/4, x+1/4, z−1/4; (ii) −x+1/2, −y+3/2, −z+1/2; (iii) −y+3/4, x+5/4, z−1/4; (iv) −x−1/2, −y+1/2, −z+1/2; (v) −y−1/4, x+5/4, z−1/4; (vi) −y+3/4, x+1/4, z−1/4; (vii) −x−1/2, −y+3/2, −z+1/2; (viii) −x+1/2, −y+1/2, −z+1/2; (ix) y−1/4, −x+1/4, −z+3/4; (x) x, y−1, z.

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