Buy article online - an online subscription or single-article purchase is required to access this article.
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
Key indicators
- Powder synchrotron study
- T = 293 K
- Mean (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
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
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.
Three impurities were identified in the sample during the Rietveld refinement: Si (9 wt%), YbSi (5 wt%) and Yb5Si3 (1 wt%).
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.
pentaytterbium tetrasilicide
top
Crystal data top
Yb5Si4 | F(000) = 1624 |
Mr = 977.54 | Dx = 7.851 (2) Mg m−3 |
Orthorhombic, Pnma | Synchrotron radiation, λ = 0.52301 Å |
Hall symbol: -p 2ac 2n | µ = 1.83 mm−1 |
a = 7.26327 (4) Å | T = 293 K |
b = 14.78061 (8) Å | Particle morphology: plate-like |
c = 7.70343 (4) Å | grey |
V = 827.01 (1) Å3 | cylinder, 50 × 0.3 mm |
Z = 4 | |
Data collection top
2-axis goniometer diffractometer | Scan method: step |
Radiation source: synchrotron, Swiss-Norwegian Beam Line BM1B | Absorption correction: for a cylinder mounted on the ϕ axis ? |
Channel-cut Si 111 monochromator | Tmin = ?, Tmax = ? |
Specimen mounting: glass capillary | 2θmin = 3.600°, 2θmax = 33.333°, 2θstep = 0.005° |
Data collection mode: transmission | |
Refinement top
Refinement on Inet | 46 parameters |
Least-squares matrix: full with fixed elements per cycle | 0 restraints |
Rp = 0.074 | 0 constraints |
Rwp = 0.096 | Weighting scheme based on measured s.u.'s |
Rexp = 0.075 | (Δ/σ)max = 0.01 |
χ2 = 1.638 | Background function: linear interpolation between 17 estimated points |
6167 data points | Preferred orientation correction: No |
Profile function: pseudo-Voigt | |
Crystal data top
Yb5Si4 | V = 827.01 (1) Å3 |
Mr = 977.54 | Z = 4 |
Orthorhombic, Pnma | Synchrotron radiation, λ = 0.52301 Å |
a = 7.26327 (4) Å | µ = 1.83 mm−1 |
b = 14.78061 (8) Å | T = 293 K |
c = 7.70343 (4) Å | cylinder, 50 × 0.3 mm |
Data collection top
2-axis goniometer diffractometer | Absorption correction: for a cylinder mounted on the ϕ axis ? |
Specimen mounting: glass capillary | Tmin = ?, Tmax = ? |
Data collection mode: transmission | 2θmin = 3.600°, 2θmax = 33.333°, 2θstep = 0.005° |
Scan method: step | |
Refinement top
Rp = 0.074 | 6167 data points |
Rwp = 0.096 | 46 parameters |
Rexp = 0.075 | 0 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 | x | y | z | Uiso*/Ueq | |
Yb1 | 0.3478 (4) | 0.25000 | 0.0188 (3) | 0.0270 (7)* | |
Yb2 | 0.0197 (2) | 0.09421 (9) | 0.1797 (2) | 0.0259 (5)* | |
Yb3 | 0.3181 (2) | 0.87800 (9) | 0.1765 (2) | 0.0233 (5)* | |
Si1 | 0.240 (2) | 0.25000 | 0.388 (2) | 0.035 (2)* | |
Si2 | 0.978 (2) | 0.25000 | 0.8822 (19) | 0.035 (2)* | |
Si3 | 0.1466 (16) | 0.9615 (6) | 0.4715 (15) | 0.035 (2)* | |
Bond lengths (Å) top
Yb1—Si2i | 2.887 (16) | Yb2—Yb3xii | 3.686 (2) |
Yb1—Si1ii | 2.939 (15) | Yb2—Yb3xiii | 3.704 (2) |
Yb1—Si1 | 2.953 (15) | Yb2—Yb2viii | 3.790 (2) |
Yb1—Si3iii | 3.147 (9) | Yb2—Yb2xiv | 3.790 (2) |
Yb1—Si3iv | 3.147 (9) | Yb2—Yb3xi | 3.861 (2) |
Yb1—Si2v | 3.229 (15) | Yb2—Yb2xv | 3.937 (2) |
Yb1—Yb3vi | 3.425 (3) | Yb2—Yb3xvi | 4.025 (2) |
Yb1—Yb3vii | 3.425 (3) | Yb2—Yb3iv | 4.072 (2) |
Yb1—Yb3iv | 3.462 (3) | Yb3—Si3xvii | 2.861 (10) |
Yb1—Yb3iii | 3.462 (3) | Yb3—Si3 | 2.871 (11) |
Yb1—Yb2ii | 3.501 (2) | Yb3—Si2xviii | 2.879 (12) |
Yb1—Yb2viii | 3.501 (2) | Yb3—Si2xix | 2.898 (12) |
Yb1—Yb2 | 3.538 (2) | Yb3—Si3viii | 2.918 (11) |
Yb1—Yb2ix | 3.538 (2) | Yb3—Si1iv | 2.947 (11) |
Yb2—Si3iv | 3.020 (12) | Yb3—Yb3xx | 3.7838 (19) |
Yb2—Si3x | 3.059 (11) | Yb3—Yb3xiv | 3.804 (2) |
Yb2—Si1v | 3.114 (10) | Yb3—Yb3viii | 3.804 (2) |
Yb2—Si3xi | 3.123 (11) | Si1—Si2xxi | 2.47 (2) |
Yb2—Si1 | 3.233 (11) | Si2—Si2xxii | 4.16 (2) |
Yb2—Si2i | 3.263 (10) | Si2—Si2xxi | 4.16 (2) |
Yb2—Si3xii | 3.543 (11) | Si3—Si3xxiii | 2.454 (16) |
Symmetry codes: (i) x−1, y, z−1; (ii) x+1/2, −y+1/2, −z+1/2; (iii) −x+1/2, y−1/2, z−1/2; (iv) −x+1/2, −y+1, z−1/2; (v) x−1/2, −y+1/2, −z+1/2; (vi) −x+1, y−1/2, −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, y−1, z; (xii) x−1/2, y−1, −z+1/2; (xiii) −x, −y+1, −z; (xiv) x−1/2, y, −z+1/2; (xv) −x, −y, −z; (xvi) −x+1/2, −y+1, z+1/2; (xvii) −x+1/2, −y+2, z−1/2; (xviii) −x+3/2, −y+1, z−1/2; (xix) −x+1, y+1/2, −z+1; (xx) x, −y+3/2, z; (xxi) x−1/2, −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 formula | Yb5Si4 |
Mr | 977.54 |
Crystal system, space group | Orthorhombic, Pnma |
Temperature (K) | 293 |
a, b, c (Å) | 7.26327 (4), 14.78061 (8), 7.70343 (4) |
V (Å3) | 827.01 (1) |
Z | 4 |
Radiation type | Synchrotron, λ = 0.52301 Å |
µ (mm−1) | 1.83 |
Specimen shape, size (mm) | Cylinder, 50 × 0.3 |
|
Data collection |
Diffractometer | 2-axis goniometer diffractometer |
Specimen mounting | Glass capillary |
Data collection mode | Transmission |
Scan method | Step |
2θ values (°) | 2θmin = 3.600 2θmax = 33.333 2θstep = 0.005 |
|
Refinement |
R factors and goodness of fit | Rp = 0.074, Rwp = 0.096, Rexp = 0.075, χ2 = 1.638 |
No. of data points | 6167 |
No. of parameters | 46 |
Selected bond lengths (Å) topYb1—Si2i | 2.887 (16) | Yb2—Yb3ix | 3.686 (2) |
Yb1—Si1ii | 2.939 (15) | Yb2—Yb3x | 3.704 (2) |
Yb1—Si1 | 2.953 (15) | Yb2—Yb2xi | 3.790 (2) |
Yb1—Si3iii | 3.147 (9) | Yb2—Yb3viii | 3.861 (2) |
Yb1—Si2iv | 3.229 (15) | Yb2—Yb2xii | 3.937 (2) |
Yb1—Yb3v | 3.425 (3) | Yb3—Si3xiii | 2.861 (10) |
Yb1—Yb3vi | 3.462 (3) | Yb3—Si3 | 2.871 (11) |
Yb1—Yb2ii | 3.501 (2) | Yb3—Si2xiv | 2.879 (12) |
Yb1—Yb2 | 3.538 (2) | Yb3—Si2xv | 2.898 (12) |
Yb2—Si3vi | 3.020 (12) | Yb3—Si3xi | 2.918 (11) |
Yb2—Si3vii | 3.059 (11) | Yb3—Si1vi | 2.947 (11) |
Yb2—Si1iv | 3.114 (10) | Yb3—Yb3xvi | 3.7838 (19) |
Yb2—Si3viii | 3.123 (11) | Yb3—Yb3xvii | 3.804 (2) |
Yb2—Si1 | 3.233 (11) | Si1—Si2xviii | 2.47 (2) |
Yb2—Si2i | 3.263 (10) | Si3—Si3xix | 2.454 (16) |
Yb2—Si3ix | 3.543 (11) | | |
Symmetry codes: (i) x−1, y, z−1; (ii) x+1/2, −y+1/2, −z+1/2; (iii) −x+1/2, y−1/2, z−1/2; (iv) x−1/2, −y+1/2, −z+1/2; (v) −x+1, y−1/2, −z; (vi) −x+1/2, −y+1, z−1/2; (vii) −x, −y+1, −z+1; (viii) x, y−1, z; (ix) x−1/2, y−1, −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, z−1/2; (xiv) −x+3/2, −y+1, z−1/2; (xv) −x+1, y+1/2, −z+1; (xvi) x, −y+3/2, z; (xvii) x−1/2, y, −z+1/2; (xviii) x−1/2, −y+1/2, −z+3/2; (xix) −x, −y+2, −z+1. |
Subscribe to Acta Crystallographica Section E: Crystallographic Communications
The full text of this article is available to subscribers to the journal.
If you have already registered and are using a computer listed in your registration details, please email
support@iucr.org for assistance.
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.