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The crystal structures of the new isomorphous compounds iron(III) oxyfluoro­tellurate(IV), FeTeO3F, gallium(III) oxy­fluoro­tellurate(IV), GaTeO3F, and chromium(III) oxyfluoro­tellurate(IV), CrTeO3F, consist of zigzag chains of MO4F2 distorted octa­hedra alternately sharing O-O and F-F edges and connected via TeO3 trigonal pyramids. A full O/F anionic ordering is observed and the electronic lone pair of the TeIV cation is stereochemically active.

Supporting information

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Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270107062683/sq3115sup1.cif
Contains datablocks I, II, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270107062683/sq3115Isup2.hkl
Contains datablock I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270107062683/sq3115IIsup3.hkl
Contains datablock II

Comment top

In recent years, a systematic investigation of tellurium(IV) fluorides and oxyfluorides has been performed in our laboratory in order to develop our knowledge in four directions: (i) synthesis of new phases of potential interest for their nonlinear optical properties; (ii) characterization of new structure types in order to determine the influence of the electronic lone pair of TeIV atoms (E) on their structural framework, especially in fluorides and oxyfluorides, compounds very sensitive to the stereochemical activity of this electronic lone pair; (iii) determination of the main rules governing the O/F anionic long-range or short-range ordering in oxyfluorides; and (iv) crystal growth in hydrofluoric acid medium of tellurates and oxyfluorotellurates(IV), which could be promising for nonlinear optics.

Following on the structural characterization of the TeOF2 (Guillet et al., 1999), Te2O3F2 (Ider et al., 1996) and KTe3O6F (Laval et al., 2002) phases, this paper deals with the synthesis and the crystal structure determination of a new isostructural series of oxyfluorides, MTeO3F, with M = FeIII, GaIII and CrIII.

The Te atom is bonded to three O atoms at distances of ca 1.9 Å (Tables 1 and 2). It occupies the centre of a trigonal pyramid with the stereochemically active electronic lone pair E pointing to the direction of the fourth corner (Fig. 1). If three weak extra bonds with lengths of ca 2.7 Å are considered, the anionic polyhedron can be described as a distorted octahedron. The lone pair E occupies the volume formed between the Te atom and the weakly bonded anions. The M atom is sixfold coordinated, slightly shifted from the center of a distorted MO4F2 octahedron (Fig. 2, and Tables 1 and 2). Bond valence calculations (Brown, 1981) are consistent with the description MIIITeIV(O2-)3F- showing a full O/F ordering (Tables 3 and 4).

FeTeO3F, GaTeO3F and CrTeO3F [with lattice parameters refined on the basis of powder X-ray diffraction data of a = 5.028 (1) Å, b = 5.073 (1) Å, c = 12.307 (2) Å and β = 97.40 (4)°, using the refinement program CHEKCELL (Laugier & Bochu, 2000)] are isostructural with `zigzag' chains of MO4F2 (M = FeIII, GaIII and CrIII) distorted octahedra sharing alternately O–O and F–F edges and interconnected via TeO3 trigonal pyramids (Fig. 3a). A projection onto (010) shows large tunnels parallel to [010], towards which point the lone pairs E (Fig. 3b). The description considering the Te anionic environment as a distorted octahedron (Fig. 1) allows an interesting comparison with the α-PbO2 (Fig. 4) structure (Hyde & Andersson, 1989). Indeed, the structure of MTeO3F (M = FeIII, GaIII and CrIII; Fig. 3a) is thus based on parallel zigzag chains of corner-sharing octahedra, two adjacent chains being shifted by a/2 along the [001] direction. The idealized MTeO3F structure appears as a superstructure of α-PbO2 with doubling of the c axis (Table 5). However, the hexagonal close packed (hcp) anionic array and the positions of the cations are more distorted than in α-PbO2 as a consequence of the cationic ordering, of the difference in size between MIII and TeIV cations, and of the stereochemical activity of the lone pair E. A strong monoclinic distortion of the lattice also occurs in the MTeO3F phases, but the analogy is worth noting.

The new MTeO3F structure type is important because it shows that oxyfluorotellurates associating the TeIV cation with trivalent cations presenting octahedral coordination can adopt a structure type derived from a classical oxide such as α-PbO2, with a distorted hcp anionic array and full cationic ordering in parallel zigzag rows. It also corresponds to an intergrowth of MOF and TeO2 slabs with F- anions only bonded to MIII cations. There is no strong Te—F bond, sensitive to hydrolysis, so this kind of phase is air-stable and could be of interest for applications in optical devices. Moreover, the unusual environment of MIII cations, interconnected by alternate F–F and O—O edges, offers the potential of promising magnetic properties.

Related literature top

For related literature, see: Brown (1981); Bruker (2004); Guillet et al. (1999); Hyde & Andersson (1989); Ider et al. (1996); Laugier & Bochu (2000); Laval et al. (2002); Sheldrick (1997).

Experimental top

Fe2O3, Cr2O3 and Ga2O3 were commercial products (Aldrich, 99.9%) and TeO2 was prepared in the laboratory by decomposition of commercial H6TeO6 (Aldrich, 99.9%) at 823 K under flowing oxygen. FeTeO3F and GaTeO3F were prepared in two steps: first an intimate mixture (mol%) of 1/2Fe2O3-4TeO2 (or 1/2Ga2O3-2TeO2) was dissolved in hydrofluoric acid (40%) in a Teflon beaker and heated at 453 K and then, after slow evaporation, the product was crushed and heated in a platinum sealed tube. The temperature was progressively increased to 723 K (923 K for Ga phase) (5 K min-1), kept stable for 96 h, then slowly decreased to 673 K (0.05 K min-1 for Fe and 0.1 K min-1 for Ga), and finally stabilized for 10 h. After that, the tube was water-quenched down to room temperature. Green crystals of FeTeO3F and colorless crystals of GaTeO3F, air-stable and suitable for X-ray diffraction study, were obtained. The chromium phase was obtained in powder form by direct heating of a Cr2O3–CrF3–3TeO2 mixture in a platinum sealed tube. The temperature was progressively increased to 973 K (5 K min-1) and kept stable for 96 h. The tube was then water-quenched.

Refinement top

The integrated intensities were corrected for absorption effects by using a multi-scan method (SADABS, Bruker 2004). Structure solution by direct methods in the P21/n space group followed by refinement of atomic coordinates and anisotropic thermal parameters were performed using successively the SHELXS97 and the SHELXL97 programs (Sheldrick, 1997).

Computing details top

For both compounds, data collection: KappaCCD Server Software (Nonius, 1997); cell refinement: DIRAX/LSQ (Duisenberg & Schreurs, 2000); data reduction: EVALCCD (Duisenberg & Schreurs, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 2001); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures top
[Figure 1] Fig. 1. The anionic polyhedron (distorted octahedron) around the Te atom in the FeTeO3F structure. The arrow indicates the direction towards which the lone pair E points. The Ga and Cr analogs are isostructural. [Symmetry codes: (i) -x + 1/2, y - 1/2, -z + 3/2; (ii) -x + 3/2, y - 1/2, -z + 3/2.]
[Figure 2] Fig. 2. The coordination polyhedron of the Fe atom in FeTeO3F. [Symmetry codes: (i) -x + 1/2, y - 1/2, -z + 3/2; (ii) -x + 3/2, y - 1/2, -z + 3/2; (iii) -x + 1, -y + 2, -z + 1; (iv) x - 1/2, -y + 3/2, z - 1/2.]
[Figure 3] Fig. 3. (a) The (100) layer of `zigzag' (FeO3F)n chains of FeO4F2 octahedra connected via TeO3. (b) A projection onto (010) showing the tunnels into which the lone pairs E point.
[Figure 4] Fig. 4. The ideal structure of α-PbO2 for comparison with the structure of FeTeO3F (see Fig. 3a).
(I) iron(III) oxyfluorotellurates(IV) top
Crystal data top
FeTeO3FF(000) = 444
Mr = 250.45Dx = 5.286 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P2ynCell parameters from 4316 reflections
a = 5.0667 (7) Åθ = 5.2–30.0°
b = 5.0550 (7) ŵ = 13.73 mm1
c = 12.3975 (15) ÅT = 293 K
β = 97.630 (13)°Irregular tablet shape, green
V = 314.72 (7) Å30.10 × 0.04 × 0.02 mm
Z = 4
Data collection top
Nonius KappaCCD
diffractometer
903 independent reflections
Radiation source: fine-focus sealed tube757 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.058
Detector resolution: 9 pixels mm-1θmax = 30.0°, θmin = 5.2°
CCD scansh = 77
Absorption correction: multi-scan
(SADABS; Bruker 2004)
k = 77
Tmin = 0.337, Tmax = 0.763l = 1617
10518 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.021 w = 1/[σ2(Fo2) + (0.0187P)2]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.036(Δ/σ)max = 0.001
S = 0.99Δρmax = 0.88 e Å3
903 reflectionsΔρmin = 0.95 e Å3
56 parametersExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.0020 (3)
Crystal data top
FeTeO3FV = 314.72 (7) Å3
Mr = 250.45Z = 4
Monoclinic, P21/nMo Kα radiation
a = 5.0667 (7) ŵ = 13.73 mm1
b = 5.0550 (7) ÅT = 293 K
c = 12.3975 (15) Å0.10 × 0.04 × 0.02 mm
β = 97.630 (13)°
Data collection top
Nonius KappaCCD
diffractometer
903 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker 2004)
757 reflections with I > 2σ(I)
Tmin = 0.337, Tmax = 0.763Rint = 0.058
10518 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.02156 parameters
wR(F2) = 0.0360 restraints
S = 0.99Δρmax = 0.88 e Å3
903 reflectionsΔρmin = 0.95 e Å3
Special details top

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.

The integrated intensities were corrected for absorption effects by using a multi-scan method (SADABS, Bruker 2004). Structure solution by direct methods in the P21/n space group followed by refinement of atomic coordinates and anisotropic thermal parameters were performed using successively the SHELXS97 and the SHELXL97 programs (Sheldrick, 1997).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Te10.51067 (4)0.80699 (5)0.831702 (17)0.00620 (8)
Fe10.46203 (10)0.74548 (9)0.57193 (4)0.00643 (12)
F10.2720 (4)1.0638 (4)0.51074 (15)0.0087 (4)
O10.2994 (5)1.1099 (5)0.84327 (19)0.0111 (5)
O20.8067 (5)0.9335 (4)0.92872 (18)0.0084 (5)
O30.6280 (5)0.9215 (5)0.70277 (18)0.0083 (5)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Te10.00642 (12)0.00694 (12)0.00519 (12)0.00043 (9)0.00061 (8)0.00021 (9)
Fe10.0082 (3)0.0057 (2)0.0052 (2)0.00031 (18)0.00035 (19)0.00039 (17)
F10.0105 (11)0.0048 (10)0.0112 (10)0.0013 (8)0.0026 (8)0.0020 (8)
O10.0112 (14)0.0124 (13)0.0103 (12)0.0071 (10)0.0030 (10)0.0003 (10)
O20.0105 (13)0.0068 (13)0.0069 (12)0.0017 (10)0.0031 (9)0.0013 (9)
O30.0105 (13)0.0088 (12)0.0056 (11)0.0019 (10)0.0006 (10)0.0008 (9)
Geometric parameters (Å, º) top
Te1—O31.870 (2)Fe1—F1iii2.040 (2)
Te1—O11.884 (2)Fe1—O2iv2.054 (2)
Te1—O21.904 (2)F1—Fe1iii2.040 (2)
Fe1—O1i1.923 (2)O1—Fe1v1.923 (2)
Fe1—O31.941 (2)O1—O32.736 (3)
Fe1—O2ii1.965 (2)O2—Fe1vi1.965 (2)
Fe1—F11.9743 (19)O2—Fe1vii2.054 (2)
O3—Te1—O193.55 (10)O1i—Fe1—O2iv95.91 (10)
O3—Te1—O297.05 (10)O3—Fe1—O2iv176.35 (10)
O1—Te1—O294.99 (10)O2ii—Fe1—O2iv78.65 (10)
O1i—Fe1—O387.71 (10)F1—Fe1—O2iv85.15 (9)
O1i—Fe1—O2ii99.81 (11)F1iii—Fe1—O2iv88.66 (9)
O3—Fe1—O2ii100.30 (10)Fe1—F1—Fe1iii104.92 (9)
O1i—Fe1—F199.47 (10)Te1—O1—Fe1v140.40 (14)
O3—Fe1—F194.74 (9)Fe1v—O1—O3173.54 (13)
O2ii—Fe1—F1155.93 (10)Te1—O2—Fe1vi133.38 (12)
O1i—Fe1—F1iii172.62 (10)Te1—O2—Fe1vii125.27 (12)
O3—Fe1—F1iii87.79 (9)Fe1vi—O2—Fe1vii101.35 (10)
O2ii—Fe1—F1iii86.75 (9)Te1—O3—Fe1114.89 (12)
F1—Fe1—F1iii75.08 (9)
Symmetry codes: (i) x+1/2, y1/2, z+3/2; (ii) x+3/2, y1/2, z+3/2; (iii) x+1, y+2, z+1; (iv) x1/2, y+3/2, z1/2; (v) x+1/2, y+1/2, z+3/2; (vi) x+3/2, y+1/2, z+3/2; (vii) x+1/2, y+3/2, z+1/2.
(II) gallium(III) oxyfluorotellurates(IV) top
Crystal data top
GaTeO3FF(000) = 464
Mr = 264.32Dx = 5.771 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P2ynCell parameters from 4415 reflections
a = 5.0625 (7) Åθ = 5.3–29.9°
b = 4.9873 (7) ŵ = 18.29 mm1
c = 12.1662 (15) ÅT = 293 K
β = 97.952 (13)°Irregular tablet shape, colourless
V = 304.22 (7) Å30.10 × 0.04 × 0.02 mm
Z = 4
Data collection top
Nonius KappaCCD
diffractometer
867 independent reflections
Radiation source: fine-focus sealed tube831 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.036
Detector resolution: 9 pixels mm-1θmax = 29.9°, θmin = 5.3°
CCD scansh = 77
Absorption correction: multi-scan
(SADABS; Bruker 2004)
k = 66
Tmin = 0.257, Tmax = 0.697l = 1717
8547 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.017 w = 1/[σ2(Fo2) + (0.0243P)2 + 0.1503P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.042(Δ/σ)max = 0.001
S = 1.21Δρmax = 1.25 e Å3
867 reflectionsΔρmin = 1.71 e Å3
56 parametersExtinction correction: SHELXL97, Fc^*^=kFc[1+0.001xFc^2^λ^3^/sin(2θ)]^-1/4^
0 restraintsExtinction coefficient: 0.134 (3)
Crystal data top
GaTeO3FV = 304.22 (7) Å3
Mr = 264.32Z = 4
Monoclinic, P21/nMo Kα radiation
a = 5.0625 (7) ŵ = 18.29 mm1
b = 4.9873 (7) ÅT = 293 K
c = 12.1662 (15) Å0.10 × 0.04 × 0.02 mm
β = 97.952 (13)°
Data collection top
Nonius KappaCCD
diffractometer
867 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker 2004)
831 reflections with I > 2σ(I)
Tmin = 0.257, Tmax = 0.697Rint = 0.036
8547 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.01756 parameters
wR(F2) = 0.0420 restraints
S = 1.21Δρmax = 1.25 e Å3
867 reflectionsΔρmin = 1.71 e Å3
Special details top

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 F^2^ against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F^2^, conventional R-factors R are based on F, with F set to zero for negative F^2^. The threshold expression of F^2^ > σ(F^2^) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F^2^ 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
Te10.50765 (3)0.80831 (4)0.831228 (16)0.00437 (10)
Ga10.46192 (7)0.74406 (7)0.57025 (3)0.00454 (11)
F10.2769 (3)1.0620 (4)0.51144 (14)0.0072 (4)
O10.3025 (4)1.1196 (5)0.84307 (18)0.0100 (4)
O20.8114 (4)0.9345 (5)0.92943 (17)0.0063 (4)
O30.6268 (4)0.9235 (5)0.70071 (16)0.0064 (4)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Te0.00263 (13)0.00658 (16)0.00409 (13)0.00022 (6)0.00119 (7)0.00022 (6)
Ga0.00399 (17)0.0056 (2)0.00422 (18)0.00026 (12)0.00134 (12)0.00029 (11)
F10.0064 (8)0.0068 (9)0.0084 (8)0.0009 (7)0.0020 (6)0.0015 (7)
O10.0089 (10)0.0129 (12)0.0087 (10)0.0049 (9)0.0031 (8)0.0002 (9)
O20.0057 (9)0.0062 (10)0.0059 (9)0.0024 (8)0.0033 (7)0.0012 (8)
O30.0075 (9)0.0086 (11)0.0035 (9)0.0031 (8)0.0017 (7)0.0003 (8)
Geometric parameters (Å, º) top
Te1—O31.865 (2)Ga1—O2iii1.987 (2)
Te1—O11.884 (2)Ga1—F1iv2.0089 (18)
Te1—O21.918 (2)F1—Ga1iv2.0089 (18)
Ga1—O31.911 (2)O1—Ga1v1.918 (2)
Ga1—O1i1.918 (2)O2—Ga1vi1.923 (2)
Ga1—O2ii1.923 (2)O2—Ga1vii1.987 (2)
Ga1—F11.9285 (19)
O3—Te1—O193.31 (10)F1—Ga1—O2iii86.55 (8)
O3—Te1—O295.94 (9)O3—Ga1—F1iv86.77 (8)
O1—Te1—O294.87 (10)O1i—Ga1—F1iv170.05 (9)
O3—Ga1—O1i87.29 (9)O2ii—Ga1—F1iv87.36 (9)
O3—Ga1—O2ii100.51 (9)F1—Ga1—F1iv74.92 (8)
O1i—Ga1—O2ii101.58 (10)O2iii—Ga1—F1iv89.39 (8)
O3—Ga1—F193.26 (9)Ga1—F1—Ga1iv105.08 (8)
O1i—Ga1—F197.46 (9)Te1—O1—Ga1v137.95 (13)
O2ii—Ga1—F1156.91 (8)Te1—O2—Ga1vi133.73 (12)
O3—Ga1—O2iii176.07 (9)Te1—O2—Ga1vii124.67 (12)
O1i—Ga1—O2iii96.62 (9)Ga1vi—O2—Ga1vii101.56 (9)
O2ii—Ga1—O2iii78.44 (9)Te1—O3—Ga1114.04 (11)
Symmetry codes: (i) x+1/2, y1/2, z+3/2; (ii) x+3/2, y1/2, z+3/2; (iii) x1/2, y+3/2, z1/2; (iv) x+1, y+2, z+1; (v) x+1/2, y+1/2, z+3/2; (vi) x+3/2, y+1/2, z+3/2; (vii) x+1/2, y+3/2, z+1/2.

Experimental details

(I)(II)
Crystal data
Chemical formulaFeTeO3FGaTeO3F
Mr250.45264.32
Crystal system, space groupMonoclinic, P21/nMonoclinic, P21/n
Temperature (K)293293
a, b, c (Å)5.0667 (7), 5.0550 (7), 12.3975 (15)5.0625 (7), 4.9873 (7), 12.1662 (15)
β (°) 97.630 (13) 97.952 (13)
V3)314.72 (7)304.22 (7)
Z44
Radiation typeMo KαMo Kα
µ (mm1)13.7318.29
Crystal size (mm)0.10 × 0.04 × 0.020.10 × 0.04 × 0.02
Data collection
DiffractometerNonius KappaCCD
diffractometer
Nonius KappaCCD
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker 2004)
Multi-scan
(SADABS; Bruker 2004)
Tmin, Tmax0.337, 0.7630.257, 0.697
No. of measured, independent and
observed [I > 2σ(I)] reflections
10518, 903, 757 8547, 867, 831
Rint0.0580.036
(sin θ/λ)max1)0.7030.702
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.021, 0.036, 0.99 0.017, 0.042, 1.21
No. of reflections903867
No. of parameters5656
Δρmax, Δρmin (e Å3)0.88, 0.951.25, 1.71

Computer programs: KappaCCD Server Software (Nonius, 1997), DIRAX/LSQ (Duisenberg & Schreurs, 2000), EVALCCD (Duisenberg & Schreurs, 2000), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), DIAMOND (Brandenburg, 2001).

Table 1 top
Selected bond lengths (Å) for compound (I).
Te1 – O31.870 (2)Fe1 – O1i1.923 (2)
Te1 – O11.884 (2)Fe1 – O31.941 (2)
Te1 – O21.904 (2)Fe1 – O2ii1.965 (2)
Te1 – O1i2.695 (2)Fe1 – F11.974 (2)
Te1 – O3ii2.746 (2)Fe1 – F1iii2.040 (2)
Te1 – F1i2.850 (3)Fe1 – O2iv2.054 (2)
Symmetry codes: (i) -x + 1/2, y - 1/2, -z + 3/2; (ii) -x + 3/2, y - 1/2, -z + 3/2; (iii) - x + 1, - y + 2, - z + 1; (iv) x - 1/2, -y + 3/2, z - 1/2.
Table 2 top
Selected bond lengths (Å) for compound (II).
Te1 – O31.865 (2)Ga1 – O1i1.918 (2)
Te1 – O11.884 (2)Ga1 – O31.911 (2)
Te1 – O21.918 (2)Ga1 – O2ii1.923 (2)
Te1 – O1i2.632 (2)Ga1 – F11.929 (2)
Te1 – O3ii2.731 (2)Ga1 – F1iii2.009 (2)
Te1 – F1i2.830 (2)Ga1 – O2iv1.987 (2)
Symmetry codes: (i) -x + 1/2, y - 1/2, -z + 3/2; (ii) -x + 3/2, y - 1/2, -z + 3/2; (iii) -x + 1, -y + 2, -z + 1; (iv) x - 1/2, -y + 3/2, z - 1/2.
Table 3 top
Bond valences for compound (I).
Fe1Te1Vij
O10.6001.286/0.1442.03
O20.536/0.4211.2182.18
O30.5761.335/0.1252.04
F10.417/0.3490.0710.84
Vij2.904.18
Table 4 top
Bond valences for compound (II).
Ga1Te1Vij
O10.6021.286/0.172.06
O20.594/0.4991.1732.27
O30.6131.354/0.132.10
F10.480/0.3860.0960.96
Vij3.174.21
Table 5 top
Comparaison of lattice parameters (Å) of FeTeO3F and α-PbO2.
FeTeO3Fa-PbO2
a = 5.067a = 4.989
b = 5.055 ; β = 97.63c = 5.466
c = 12.398 = 2 × 6.199b = 5.947
Monoclinic P21/nOrthorhombic Pbcn
 

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