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The X-ray single-crystal structure of trilithium antimony tetraoxide, Li3SbO4, is compared with the Rietveld refinement previously reported for the same material. An analysis of the geometric parameters and s.u.'s extracted from both refinements shows that, as expected, powder data yield a less accurate structure. Nevertheless, both refinements give correct geometric parameters within s.u.'s characteristic of each technique.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101007569/br1318sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270101007569/br1318Isup2.hkl
Contains datablock I

Comment top

The crystal structure of Li3SbO4 was first reported from X-ray powder diffraction data (Blasse, 1963), but was refined in a wrong space group. A more recent study determined the correct structure of this oxide (Skakle et al., 1996), described as an ordered rocksalt-type compound with distorted MO6 octahedra (M = Sb, Li). It crystallizes in the P2/c space group and the structure was refined by the Rietveld method using X-ray powder diffraction data from a Stoe Stadi/P psd-based system. This work has now been extended by a single-crystal structure refinement (Fig. 1) in order to assess the accuracy of both methods in the determination of geometric parameters. Reflections that were omitted for the powder refinement could be included in the present study, which resulted in some adjustments of the cell parameters and the atomic coordinates. Apparent discrepancies between both refinements are discussed.

A direct comparison of the s.u.'s for the geometric parameters clearly favours the single-crystal refinement; the observed range for the uncertainties of the 12 independent bond lengths is 0.002–0.009 Å for the present study (see Table 1) versus 0.01–0.08 Å for the Rietveld refinement. Moreover, the differences in bond lengths from both methods seem to be large, ranging from 0 to 0.128 Å. However, the application of a classical probabilistic test (Glusker et al., 1994) shows that these differences are not significant. Computing the parameter q, which measures the relationship of the difference between two bond lengths (Δd) respective to the s.u.'s (σ1 and σ2), i.e. q = Δd/(σ12 + σ22)1/2, it can be seen that only two differences in bond lengths between both refinements are probably significant [q = 3.63 for Sb1—O1 = 2.047 (2) Å and q = 3.10 for Li1—O1 = 2.214 (7) Å], one difference is borderline [q = 2.63 for Li1—O2 = 2.107 (7) Å], while the remaining differences are not significant (q in the range 0–2.06).

The same test applied separately for each refinement indicates the significance of the differences in bond lengths, regardless of the technique used. It is clear that for the single-crystal refinement, the three Sb—O bond lengths are not equivalent, with q values ranging from 15.56 to 41.72, while with the Rietveld data, the test is somewhat ambiguous, with a range of 1.41–4.24 for q. In the same way, the refinement based on single-crystal data indicates that the geometries around the Li atoms is severely distorted from an ideal octahedral environment; the calculated q ranges are 5.25–10.81, 1.34–27.13 and 1.40–49.33 for Li1, Li2 and Li3, respectively. In the case of the Rietveld refinement data, corresponding ranges are substantially smaller, 3.88–6.01, 0.71–1.82 and 0.95–12.13, respectively, leading to a less accurate description of the structure. For instance, the three Li2—O bond lengths determined by Rietveld are not significantly different, leading to a poor description of the coordination geometry for this atom.

Similar observations can be made for the O—M—O angles (M = Sb, Li). The s.u.'s are in the range 0.5–4.0° for the Rietveld data and 0.10–0.18° for the present work, with a more accurate description of the structure in the latter case.

Finally, it should be mentioned that the differences observed in the lattice parameters are too small to account for the differences observed in the geometric parameters, even though it was claimed many times that the cell constant s.u.'s obtained from a four-circle diffractometer may be widely over-optimistic (Jones, 1984; Sheldrick, 1997). In the present case, the relative difference between the cell volumes is under 0.6%.

In conclusion, the geometric parameters for the title compound are the same for the Rietveld and single-crystal refinements. Nevertheless, the geometry based on the Rietveld data is not as accurate, especially for the light atoms. This point justifies, in a general case, that a Rietveld refinement should be complemented, if possible, by a single-crystal study.

Related literature top

For related literature, see: Blasse (1963); Glusker et al. (1994); Jones (1984); Sheldrick (1997); Skakle et al. (1996).

Experimental top

Crystals of the Li3SbO4 oxide were grown by the total synthesis from appropriate amounts of high-purity reagents, Li2CO3 and Sb2O5. Details of the procedure were reported previously (Skakle et al., 1996).

Computing details top

Data collection: XSCANS (Fait, 1991); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXTL-Plus (Sheldrick, 1995); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL-Plus; software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The structure of the title compound in a projection normal to [100]. SbO6 octahedra form zigzag infinite chains parallel to csinβ. Displacement ellipsoids are drawn at the 75% probability level [symmetry codes: (i) -x, y, 1/2 - z; (ii) -x, -y, -z; (iii) x, -y, 1/2 + z].
(I) top
Crystal data top
Li3SbO4F(000) = 184
Mr = 206.57Dx = 4.518 Mg m3
Dm = 4.354 Mg m3
Dm measured by pycnometer
Monoclinic, P2/cMo Kα radiation, λ = 0.71073 Å
a = 5.1456 (5) ÅCell parameters from 44 reflections
b = 6.0794 (5) Åθ = 4.2–13.8°
c = 5.1291 (6) ŵ = 8.90 mm1
β = 108.859 (8)°T = 293 K
V = 151.84 (3) Å3Needle, white
Z = 20.7 × 0.1 × 0.1 mm
Data collection top
Siemens P4
diffractometer
342 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.026
Graphite monochromatorθmax = 27.5°, θmin = 3.4°
2θ/ω scansh = 66
Absorption correction: ψ scan
XSCANS (Fait, 1991)
k = 77
Tmin = 0.782, Tmax = 0.899l = 66
774 measured reflections2 standard reflections every 48 reflections
355 independent reflections intensity decay: 1.7%
Refinement top
Refinement on F2Primary atom site location: From the published Rietveld refinement for the same material. See Skakle et al., J. Mater. Chem., 1996, 6, 1939-1942
Least-squares matrix: fullSecondary atom site location: none
R[F2 > 2σ(F2)] = 0.015 w = 1/[σ2(Fo2) + (0.011P)2]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.036(Δ/σ)max = 0.001
S = 1.04Δρmax = 0.58 e Å3
355 reflectionsΔρmin = 1.04 e Å3
40 parametersExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.024 (2)
Crystal data top
Li3SbO4V = 151.84 (3) Å3
Mr = 206.57Z = 2
Monoclinic, P2/cMo Kα radiation
a = 5.1456 (5) ŵ = 8.90 mm1
b = 6.0794 (5) ÅT = 293 K
c = 5.1291 (6) Å0.7 × 0.1 × 0.1 mm
β = 108.859 (8)°
Data collection top
Siemens P4
diffractometer
342 reflections with I > 2σ(I)
Absorption correction: ψ scan
XSCANS (Fait, 1991)
Rint = 0.026
Tmin = 0.782, Tmax = 0.8992 standard reflections every 48 reflections
774 measured reflections intensity decay: 1.7%
355 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.01540 parameters
wR(F2) = 0.0360 restraints
S = 1.04Δρmax = 0.58 e Å3
355 reflectionsΔρmin = 1.04 e Å3
Special details top

Experimental. 4 Octants were measured for the monoclinic cell and Friedel were merged.

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. PLATON detects potential lattice centering or halving and additional symmetry elements. For possible mC cells, Rint=20.9% for 514 merged reflections; For oC cell, Rint=31.5% for 612 merged reflections, while Rint=2.7% for the reported mP cell. Moreover, the γ angle for the orthorhombic cell is 90.19°.

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
xyzUiso*/Ueq
Sb10.00000.14338 (5)0.25000.00466 (15)
O10.2214 (5)0.1021 (4)0.0036 (5)0.0077 (5)
O20.2455 (5)0.3591 (4)0.0231 (5)0.0083 (5)
Li10.00000.6161 (15)0.25000.019 (2)
Li20.50000.1485 (15)0.25000.019 (2)
Li30.50000.4227 (19)0.25000.0194 (19)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Sb10.00534 (19)0.00371 (19)0.00469 (19)0.0000.00130 (11)0.000
O10.0077 (11)0.0072 (12)0.0088 (11)0.0005 (9)0.0034 (9)0.0024 (8)
O20.0086 (11)0.0062 (11)0.0074 (11)0.0012 (9)0.0011 (9)0.0017 (8)
Li10.026 (5)0.009 (5)0.019 (5)0.0000.002 (4)0.000
Li20.015 (5)0.011 (4)0.030 (5)0.0000.007 (4)0.000
Li30.018 (5)0.025 (5)0.020 (4)0.0000.013 (4)0.000
Geometric parameters (Å, º) top
Sb1—O2i1.929 (2)Li1—O2i2.107 (7)
Sb1—O21.929 (2)Li1—O2vii2.174 (3)
Sb1—O1i2.003 (2)Li1—O2iv2.174 (3)
Sb1—O12.003 (2)Li1—O1vii2.214 (7)
Sb1—O1ii2.047 (2)Li1—O1iv2.214 (7)
Sb1—O1iii2.047 (2)Li2—O2viii2.032 (6)
O1—Sb1ii2.047 (2)Li2—O1ix2.205 (6)
O1—Li2ii2.205 (6)Li2—O1ii2.205 (6)
O1—Li1iv2.214 (7)Li2—O1x2.214 (3)
O1—Li2v2.214 (3)Li2—O1xi2.214 (3)
O1—Li3v2.518 (9)Li3—O2xii2.050 (3)
O2—Li22.032 (6)Li3—O2vii2.062 (8)
O2—Li32.050 (3)Li3—O2vi2.062 (8)
O2—Li3vi2.062 (8)Li3—O1x2.518 (9)
O2—Li12.107 (7)Li3—O1i2.518 (9)
O2—Li1iv2.174 (3)
O2i—Sb1—O294.31 (14)O2—Li1—O2i84.3 (4)
O2i—Sb1—O1i95.31 (10)O2—Li1—O2vii92.2 (2)
O2—Sb1—O1i94.48 (10)O2i—Li1—O2vii93.7 (2)
O2i—Sb1—O194.48 (10)O2—Li1—O2iv93.7 (2)
O2—Sb1—O195.31 (10)O2i—Li1—O2iv92.2 (2)
O1i—Sb1—O1165.59 (13)O2vii—Li1—O2iv172.1 (5)
O2i—Sb1—O1ii173.42 (10)O2—Li1—O1vii174.37 (18)
O2—Sb1—O1ii89.88 (11)O2i—Li1—O1vii98.77 (10)
O1i—Sb1—O1ii89.41 (9)O2vii—Li1—O1vii83.0 (2)
O1—Sb1—O1ii80.06 (11)O2iv—Li1—O1vii90.9 (2)
O2i—Sb1—O1iii89.88 (11)O2—Li1—O1iv98.77 (10)
O2—Sb1—O1iii173.42 (10)O2i—Li1—O1iv174.37 (18)
O1i—Sb1—O1iii80.06 (11)O2vii—Li1—O1iv90.9 (2)
O1—Sb1—O1iii89.41 (9)O2iv—Li1—O1iv83.0 (2)
O1ii—Sb1—O1iii86.42 (13)O1vii—Li1—O1iv78.6 (3)
Sb1—O1—Sb1ii99.94 (11)O2—Li2—O2viii101.9 (4)
Sb1—O1—Li2ii95.82 (10)O2—Li2—O1ix173.2 (3)
Sb1ii—O1—Li2ii89.23 (18)O2viii—Li2—O1ix82.97 (10)
Sb1—O1—Li1iv88.73 (9)O2—Li2—O1ii82.97 (10)
Sb1ii—O1—Li1iv97.50 (18)O2viii—Li2—O1ii173.2 (3)
Li2ii—O1—Li1iv171.1 (2)O1ix—Li2—O1ii92.6 (3)
Sb1—O1—Li2v164.5 (3)O2—Li2—O1x94.52 (16)
Sb1ii—O1—Li2v94.26 (19)O2viii—Li2—O1x94.70 (16)
Li2ii—O1—Li2v90.4 (2)O1ix—Li2—O1x80.28 (18)
Li1iv—O1—Li2v83.3 (2)O1ii—Li2—O1x89.6 (2)
Sb1—O1—Li3v85.17 (8)O2—Li2—O1xi94.70 (16)
Sb1ii—O1—Li3v173.41 (15)O2viii—Li2—O1xi94.52 (16)
Li2ii—O1—Li3v94.4 (3)O1ix—Li2—O1xi89.6 (2)
Li1iv—O1—Li3v78.3 (2)O1ii—Li2—O1xi80.28 (18)
Li2v—O1—Li3v80.24 (19)O1x—Li2—O1xi165.3 (5)
Sb1—O2—Li297.9 (2)O2xii—Li3—O2158.3 (6)
Sb1—O2—Li3101.5 (2)O2xii—Li3—O2vii96.75 (19)
Li2—O2—Li397.0 (2)O2—Li3—O2vii97.2 (2)
Sb1—O2—Li3vi174.7 (2)O2xii—Li3—O2vi97.2 (2)
Li2—O2—Li3vi79.1 (3)O2—Li3—O2vi96.75 (19)
Li3—O2—Li3vi83.25 (19)O2vii—Li3—O2vi99.9 (5)
Sb1—O2—Li190.7 (2)O2xii—Li3—O1x77.6 (3)
Li2—O2—Li1170.2 (3)O2—Li3—O1x85.5 (3)
Li3—O2—Li185.7 (3)O2vii—Li3—O1x168.4 (4)
Li3vi—O2—Li191.9 (3)O2vi—Li3—O1x90.95 (12)
Sb1—O2—Li1iv91.8 (2)O2xii—Li3—O1i85.5 (3)
Li2—O2—Li1iv88.78 (18)O2—Li3—O1i77.6 (3)
Li3—O2—Li1iv164.5 (4)O2vii—Li3—O1i90.95 (12)
Li3vi—O2—Li1iv83.77 (18)O2vi—Li3—O1i168.4 (4)
Li1—O2—Li1iv86.3 (2)O1x—Li3—O1i78.6 (4)
Symmetry codes: (i) x, y, z+1/2; (ii) x, y, z; (iii) x, y, z+1/2; (iv) x, y+1, z; (v) x+1, y, z; (vi) x1, y+1, z; (vii) x, y+1, z+1/2; (viii) x1, y, z1/2; (ix) x1, y, z1/2; (x) x1, y, z; (xi) x, y, z1/2; (xii) x1, y, z+1/2.

Experimental details

Crystal data
Chemical formulaLi3SbO4
Mr206.57
Crystal system, space groupMonoclinic, P2/c
Temperature (K)293
a, b, c (Å)5.1456 (5), 6.0794 (5), 5.1291 (6)
β (°) 108.859 (8)
V3)151.84 (3)
Z2
Radiation typeMo Kα
µ (mm1)8.90
Crystal size (mm)0.7 × 0.1 × 0.1
Data collection
DiffractometerSiemens P4
diffractometer
Absorption correctionψ scan
XSCANS (Fait, 1991)
Tmin, Tmax0.782, 0.899
No. of measured, independent and
observed [I > 2σ(I)] reflections
774, 355, 342
Rint0.026
(sin θ/λ)max1)0.649
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.015, 0.036, 1.04
No. of reflections355
No. of parameters40
Δρmax, Δρmin (e Å3)0.58, 1.04

Computer programs: XSCANS (Fait, 1991), XSCANS, SHELXTL-Plus (Sheldrick, 1995), SHELXL97 (Sheldrick, 1997), SHELXTL-Plus, SHELXL97.

Selected bond lengths (Å) top
Sb1—O21.929 (2)Li2—O2iv2.032 (6)
Sb1—O12.003 (2)Li2—O1i2.205 (6)
Sb1—O1i2.047 (2)Li2—O1v2.214 (3)
Li1—O2ii2.107 (7)Li3—O2vi2.050 (3)
Li1—O2iii2.174 (3)Li3—O2iii2.062 (8)
Li1—O1iii2.214 (7)Li3—O1ii2.518 (9)
Symmetry codes: (i) x, y, z; (ii) x, y, z+1/2; (iii) x, y+1, z+1/2; (iv) x1, y, z1/2; (v) x, y, z1/2; (vi) x1, y, z+1/2.
 

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