Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536802023541/br6073sup1.cif | |
Rietveld powder data file (CIF format) https://doi.org/10.1107/S1600536802023541/br6073Isup2.rtv |
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.
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 |
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 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 |
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 |
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 |
Experimental. The absorption coefficient takes into account the 60% filling of the capillary. |
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)* |
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 |
Computer programs: FULLPROF99 (Rodríguez-Carvajal, 1999), FULLPROF99, ATOMS (Dowty, 1993), WinPLOTR (Roisnel & Rodríguez-Carvajal, 1998) and ATOMS.
Yb1—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. |
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.