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Orthorhombic Yb5Si4 (pentaytterbium tetrasilicide) crystallizes with the structure type Sm5Ge4. However, the two compounds differ in the coordination of some Si (Ge) atoms. Each Si atom in the structure of Yb5Si4 forms one covalent bond with another Si atom (Si-Si distances of 2.45-2.47 Å), in contrast to Sm5Ge4, where only half of the Ge atoms are covalently bonded to another Ge atom (Ge-Ge distance of 2.658 Å).

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536802023541/br6073sup1.cif
Contains datablocks global, I

rtv

Rietveld powder data file (CIF format) https://doi.org/10.1107/S1600536802023541/br6073Isup2.rtv
Contains datablock I

Key indicators

  • Powder synchrotron study
  • T = 293 K
  • Mean [sigma](Si-Si) = 0.016 Å
  • R factor = 0.000
  • wR factor = 0.000
  • Data-to-parameter ratio = 0.0

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


Red Alert Alert Level A:
GEOM_005 Alert A _geom_angle_atom_site_label_1 is missing Label identifying the atom site 1. GEOM_006 Alert A _geom_angle_atom_site_label_2 is missing Label identifying the atom site 2. GEOM_007 Alert A _geom_angle_atom_site_label_3 is missing Label identifying the atom site 3. GEOM_008 Alert A _geom_angle is missing Angle between atom sites 1, 2 and 3. General Notes
ABSMU_01 Radiation type not identified. Calculation of _exptl_absorpt_correction_mu not performed.
4 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
0 Alert Level C = Please check

Comment top

During studies of electronic properties of phases from the Yb–Si system (Alami-Yadri, 1997), a new compound, Yb5Si4, was synthesized, and the structure-type Sm5Ge4 (Smith et al., 1967) was identified from the comparison of lattice parameters and observed (Guinier films) and calculated (Sm5Ge4 structure type) intensities. This compound was recently presented as a new one in the Yb—Si system also by Palenzona et al. (2002). However, no refined atomic parameters were given. Our Rietveld refinement using the synchrotron data (Fig. 1) confirms that Yb5Si4 is isopointal with Sm5Ge4.

The structure can be best described as a stacking of three types of (0y0) layers: layer A (Fig. 2) at y = 1/4, 0.75 is flat and is formed from a 32434 net of Si atoms centred by a 44 net of Yb atoms. Layer B (Fig. 3) at y = 0, 0.5 is puckered and is formed from a 63 net of Si atoms. Layer C (Fig. 4) at y = 0.10, 0.40, 0.60, 0.90 is puckered and is formed from a 32434 net of Yb atoms, similar to the net of Si atoms found in the layer A.

The atomic coordinations are similar to those in Sm5Ge4 (Smith et al., 1967), with the exception of Si3 which forms a covalent bond with another Si3 at a distance of 2.454 Å contrary to the Ge3 in Sm5Ge4, where the closest Ge atom (Ge3) is at a distance of 3.706 Å. The same difference between the silicide and the germanide was reported also for the system Gd5(Si,Ge)4 (Pecharsky & Gschneidner, 1997), and was related to a different magnetic behaviour of the silicide and the germanide.

Experimental top

The samples were prepared using a sealed method because of the high evaporation pressure of ytterbium. Stoichiometric amounts of the elements were sealed in an evacuated tantalum tube and melted for about one minute by resistance heating.

Refinement top

Three impurities were identified in the sample during the Rietveld refinement: Si (9 wt%), YbSi (5 wt%) and Yb5Si3 (1 wt%).

Computing details top

Cell refinement: FULLPROF99 (Rodríguez-Carvajal, 1999); data reduction: FULLPROF99; program(s) used to refine structure: FULLPROF99; molecular graphics: ATOMS (Dowty, 1993); software used to prepare material for publication: WinPLOTR (Roisnel & Rodríguez-Carvajal, 1998) and ATOMS.

Figures top
[Figure 1] Fig. 1. Observed (circles) and calculated (solid line) intensities for Yb5Si4. Ticks indicate from top to bottom the positions of Bragg peaks of the main (Yb5Si4) and impurity (Si, YbSi, Yb5Si3) phases. The difference pattern appears below.
[Figure 2] Fig. 2. The structural slabs (0y0) of Yb5Si4 viewed along the b axis: A at y = 1/4, 0.75.
[Figure 3] Fig. 3. The structural slabs (0y0) of Yb5Si4 viewed along the b axis: B at y ~0, 0.5.
[Figure 4] Fig. 4. The structural slabs (0y0) of Yb5Si4 viewed along the b axis: C at y ~0.10, 0.40, 0.60, 0.90.
pentaytterbium tetrasilicide top
Crystal data top
Yb5Si4F(000) = 1624
Mr = 977.54Dx = 7.851 (2) Mg m3
Orthorhombic, PnmaSynchrotron radiation, λ = 0.52301 Å
Hall symbol: -p 2ac 2nµ = 1.83 mm1
a = 7.26327 (4) ÅT = 293 K
b = 14.78061 (8) ÅParticle morphology: plate-like
c = 7.70343 (4) Ågrey
V = 827.01 (1) Å3cylinder, 50 × 0.3 mm
Z = 4
Data collection top
2-axis goniometer
diffractometer
Scan method: step
Radiation source: synchrotron, Swiss-Norwegian Beam Line BM1BAbsorption correction: for a cylinder mounted on the ϕ axis
?
Channel-cut Si 111 monochromatorTmin = ?, Tmax = ?
Specimen mounting: glass capillary2θmin = 3.600°, 2θmax = 33.333°, 2θstep = 0.005°
Data collection mode: transmission
Refinement top
Refinement on Inet46 parameters
Least-squares matrix: full with fixed elements per cycle0 restraints
Rp = 0.0740 constraints
Rwp = 0.096Weighting scheme based on measured s.u.'s
Rexp = 0.075(Δ/σ)max = 0.01
χ2 = 1.638Background function: linear interpolation between 17 estimated points
6167 data pointsPreferred orientation correction: No
Profile function: pseudo-Voigt
Crystal data top
Yb5Si4V = 827.01 (1) Å3
Mr = 977.54Z = 4
Orthorhombic, PnmaSynchrotron radiation, λ = 0.52301 Å
a = 7.26327 (4) ŵ = 1.83 mm1
b = 14.78061 (8) ÅT = 293 K
c = 7.70343 (4) Åcylinder, 50 × 0.3 mm
Data collection top
2-axis goniometer
diffractometer
Absorption correction: for a cylinder mounted on the ϕ axis
?
Specimen mounting: glass capillaryTmin = ?, Tmax = ?
Data collection mode: transmission2θmin = 3.600°, 2θmax = 33.333°, 2θstep = 0.005°
Scan method: step
Refinement top
Rp = 0.0746167 data points
Rwp = 0.09646 parameters
Rexp = 0.0750 restraints
χ2 = 1.638
Special details top

Experimental. The absorption coefficient takes into account the 60% filling of the capillary.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Yb10.3478 (4)0.250000.0188 (3)0.0270 (7)*
Yb20.0197 (2)0.09421 (9)0.1797 (2)0.0259 (5)*
Yb30.3181 (2)0.87800 (9)0.1765 (2)0.0233 (5)*
Si10.240 (2)0.250000.388 (2)0.035 (2)*
Si20.978 (2)0.250000.8822 (19)0.035 (2)*
Si30.1466 (16)0.9615 (6)0.4715 (15)0.035 (2)*
Bond lengths (Å) top
Yb1—Si2i2.887 (16)Yb2—Yb3xii3.686 (2)
Yb1—Si1ii2.939 (15)Yb2—Yb3xiii3.704 (2)
Yb1—Si12.953 (15)Yb2—Yb2viii3.790 (2)
Yb1—Si3iii3.147 (9)Yb2—Yb2xiv3.790 (2)
Yb1—Si3iv3.147 (9)Yb2—Yb3xi3.861 (2)
Yb1—Si2v3.229 (15)Yb2—Yb2xv3.937 (2)
Yb1—Yb3vi3.425 (3)Yb2—Yb3xvi4.025 (2)
Yb1—Yb3vii3.425 (3)Yb2—Yb3iv4.072 (2)
Yb1—Yb3iv3.462 (3)Yb3—Si3xvii2.861 (10)
Yb1—Yb3iii3.462 (3)Yb3—Si32.871 (11)
Yb1—Yb2ii3.501 (2)Yb3—Si2xviii2.879 (12)
Yb1—Yb2viii3.501 (2)Yb3—Si2xix2.898 (12)
Yb1—Yb23.538 (2)Yb3—Si3viii2.918 (11)
Yb1—Yb2ix3.538 (2)Yb3—Si1iv2.947 (11)
Yb2—Si3iv3.020 (12)Yb3—Yb3xx3.7838 (19)
Yb2—Si3x3.059 (11)Yb3—Yb3xiv3.804 (2)
Yb2—Si1v3.114 (10)Yb3—Yb3viii3.804 (2)
Yb2—Si3xi3.123 (11)Si1—Si2xxi2.47 (2)
Yb2—Si13.233 (11)Si2—Si2xxii4.16 (2)
Yb2—Si2i3.263 (10)Si2—Si2xxi4.16 (2)
Yb2—Si3xii3.543 (11)Si3—Si3xxiii2.454 (16)
Symmetry codes: (i) x1, y, z1; (ii) x+1/2, y+1/2, z+1/2; (iii) x+1/2, y1/2, z1/2; (iv) x+1/2, y+1, z1/2; (v) x1/2, y+1/2, z+1/2; (vi) x+1, y1/2, z; (vii) x+1, y+1, z; (viii) x+1/2, y, z+1/2; (ix) x, y+1/2, z; (x) x, y+1, z+1; (xi) x, y1, z; (xii) x1/2, y1, z+1/2; (xiii) x, y+1, z; (xiv) x1/2, y, z+1/2; (xv) x, y, z; (xvi) x+1/2, y+1, z+1/2; (xvii) x+1/2, y+2, z1/2; (xviii) x+3/2, y+1, z1/2; (xix) x+1, y+1/2, z+1; (xx) x, y+3/2, z; (xxi) x1/2, y+1/2, z+3/2; (xxii) x+1/2, y+1/2, z+3/2; (xxiii) x, y+2, z+1.

Experimental details

Crystal data
Chemical formulaYb5Si4
Mr977.54
Crystal system, space groupOrthorhombic, Pnma
Temperature (K)293
a, b, c (Å)7.26327 (4), 14.78061 (8), 7.70343 (4)
V3)827.01 (1)
Z4
Radiation typeSynchrotron, λ = 0.52301 Å
µ (mm1)1.83
Specimen shape, size (mm)Cylinder, 50 × 0.3
Data collection
Diffractometer2-axis goniometer
diffractometer
Specimen mountingGlass capillary
Data collection modeTransmission
Scan methodStep
2θ values (°)2θmin = 3.600 2θmax = 33.333 2θstep = 0.005
Refinement
R factors and goodness of fitRp = 0.074, Rwp = 0.096, Rexp = 0.075, χ2 = 1.638
No. of data points6167
No. of parameters46

Computer programs: FULLPROF99 (Rodríguez-Carvajal, 1999), FULLPROF99, ATOMS (Dowty, 1993), WinPLOTR (Roisnel & Rodríguez-Carvajal, 1998) and ATOMS.

Selected bond lengths (Å) top
Yb1—Si2i2.887 (16)Yb2—Yb3ix3.686 (2)
Yb1—Si1ii2.939 (15)Yb2—Yb3x3.704 (2)
Yb1—Si12.953 (15)Yb2—Yb2xi3.790 (2)
Yb1—Si3iii3.147 (9)Yb2—Yb3viii3.861 (2)
Yb1—Si2iv3.229 (15)Yb2—Yb2xii3.937 (2)
Yb1—Yb3v3.425 (3)Yb3—Si3xiii2.861 (10)
Yb1—Yb3vi3.462 (3)Yb3—Si32.871 (11)
Yb1—Yb2ii3.501 (2)Yb3—Si2xiv2.879 (12)
Yb1—Yb23.538 (2)Yb3—Si2xv2.898 (12)
Yb2—Si3vi3.020 (12)Yb3—Si3xi2.918 (11)
Yb2—Si3vii3.059 (11)Yb3—Si1vi2.947 (11)
Yb2—Si1iv3.114 (10)Yb3—Yb3xvi3.7838 (19)
Yb2—Si3viii3.123 (11)Yb3—Yb3xvii3.804 (2)
Yb2—Si13.233 (11)Si1—Si2xviii2.47 (2)
Yb2—Si2i3.263 (10)Si3—Si3xix2.454 (16)
Yb2—Si3ix3.543 (11)
Symmetry codes: (i) x1, y, z1; (ii) x+1/2, y+1/2, z+1/2; (iii) x+1/2, y1/2, z1/2; (iv) x1/2, y+1/2, z+1/2; (v) x+1, y1/2, z; (vi) x+1/2, y+1, z1/2; (vii) x, y+1, z+1; (viii) x, y1, z; (ix) x1/2, y1, z+1/2; (x) x, y+1, z; (xi) x+1/2, y, z+1/2; (xii) x, y, z; (xiii) x+1/2, y+2, z1/2; (xiv) x+3/2, y+1, z1/2; (xv) x+1, y+1/2, z+1; (xvi) x, y+3/2, z; (xvii) x1/2, y, z+1/2; (xviii) x1/2, y+1/2, z+3/2; (xix) x, y+2, z+1.
 

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