inorganic compounds
K9Y3[Si12O32]F2
aUniversity of Innsbruck, Institute of Mineralogy & Petrography, Innrain 52, A-6020 Innsbruck, Austria
*Correspondence e-mail: volker.kahlenberg@uibk.ac.at
Single-crystals of the title compound, nonapotassium triyttrium dodecasilicate difluoride, were obtained from 2—Y2O3—KF. The belongs to the group of single-layer silicates and is based on silicate sheets parallel to (110). A single layer contains secondary (Q2) and tertiary (Q3) silicate tetrahedra in the ratio 1:2 and is build up from six-, eight- and twelve-membered rings. The linkage between neighboring layers is achieved by two crystallographically independent Y3+ cations, which are coordinated by six oxygen ligands in form of distorted octahedra. Charge compensation is accomplished by incorporation of additional F− anions and K+ cations in the structural channels, forming anion-centred [F2K7] groups. Apart from one K+ and one Y3+ cation (each with -1), the 30 crystallographically independent atoms reside on general positions.
synthesis experiments in the system SiOCCDC reference: 965914
Related literature
Oxosilicates which can serve as luminescent materials containing trivalent rare earth elements, monovalent alkali cations as well as fluorine anions have already been characterized (Jacobsen & Meyer, 1994; Tang et al., 2008; Schäfer & Schleid, 2007, 2011). For structures isotypic to that of the title compound, see: Tang et al. (2008). For general aspects of the crystal chemistry of silicates, see: Liebau (1985). For the definition of distortion parameters, see: Robinson et al. (1971). For bond-valence analysis, see: Brown & Altermatt (1985). For the Inorganic Database, see: ICSD (2013).
Experimental
Crystal data
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Data collection: CrysAlis PRO (Oxford Diffraction, 2006); cell CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SIR2002 (Burla et al., 2003); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ATOMS for Windows (Dowty, 2011); software used to prepare material for publication: publCIF (Westrip, 2010) and WinGX (Farrugia, 2012).
Supporting information
CCDC reference: 965914
10.1107/S1600536814001470/wm2792sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536814001470/wm2792Isup2.hkl
Single-crystals of K9Y3[Si12O32]F2 were obtained during a series of
syntheses experiments aiming on the preparation of new K(REE)-silicate fluorides. 0.1 g of the nutrient consisting of a mixture of Y2O3:SiO2 in the molar ratio 1:4 was homogenized in an agate mortar with 0.1 g KF, transferred into a platinum tube and welded shut. The container was fired in a resistance heated furnace from 373 K to 1373 K with a ramp of 50 K/h. The target temperature was held for 2 h. Subsequently, the sample was cooled down to 1073 K with a rate of 5 K/h and, finally, the temperature was reduced to 373 K with a rate of 100 K/h. The solidified melt cake was immediately crushed in an agate mortar and transferred to a glass slide under a polarizing binocular. A first optical inspection revealed the presence of two phases: a polycrystalline matrix of KF in which transparent birefrigent single-crystals up to 200 µm in size were embedded. However, a closer investigation using crossed polarizers revealed that all crystals showed a fine-scale non-merohedral making it impossible to separate a specimen consisting of only one domain state. Therefore, we finally decided to use a twinned fragment for further structural studies. The crystal was mounted on the tip of a glass fibre using finger nail hardener as glue.The diffraction patterns were collected at ambient temperature using on Oxford Diffraction Gemini R Ultra single-crystal diffractometer. They showed the expected complexity due to overlapping of two different reciprocal lattices. Nevertheless, it was possible to index the reflections from both domains with the same triclinic β is close to 90°, the non-merohedral can be readily understood. Similar sets of lattice parameters could be found in the recent WEB-based version of the Inorganic Database (ICSD, 2013) for the chemically closely related compounds K9(REE)3[Si12O32]F2 (REE = Sm, Eu, Gd) pointing to an isostructural relationship, which was confirmed by the subsequent structure analysis. For a full data set (sphere) of was collected. Different integration strategies were tested to handle the problem of the partially overlapping reflections of both domains, i.e. a series of data sets was produced in which the overlap threshold was varied stepwise. Different HKLF 5 data sets produced during integration were considered for the of the structure. However, the best results concerning residuals and overall crystallochemical characteristics of the structure were obtained when the data set of only the main twin component (representating about 70% of the total volume) was used, i.e. the completely or partially overlapping reflections have been neglected. However, this approach resulted in a completeness of only 90%.
but in different orientations. From the fact that the angleIn the present paper we describe a previously unknown phase of the system KF—Y2O3—SiO2. According to Liebau's classification (1985) the ∞}[5Si12O32]F2. A single-layer of silicate tetrahedra expands parallel to (110) and is constructed from the condensation of fünfer single chains (Fig. 1). One discrete chain is running parallel to [001] and has a translation period of 11.3727 (5) Å. Each layer contains secondary (Q2) and tertiary (Q3) SiO4 tetrahedra in the ratio of 1:2 (Fig. 2). The Si—O distances of the six crystallographically independent tetrahedra within the range from 1.574 (5) to 1.662 (5) Å. As one would expect, the Si—Oterminal bonds are considerably shorter than the distances between Si and the bridging O atoms. The O—Si—O angles show a significant scatter throughout all present polyhedra. Nevertheless, the values are in the expected limits for [SiO4] units (Liebau, 1985). Numerically, the degree of distortion can be expressed by the quadratic elongation λ and the angle variance σ2 (Robinson et al., 1971). For the six tetrahedra, these two parameters vary between 1.003 and 1.005 (for λ) and 8.50 and 20.17 (for σ2) indicating that the deviation from regularity is not very pronounced.
of the title compound, K9Y3[Si12O32]F2, belongs to the group of open-branched single-layer silicates. The more detailed crystallochemical formula can be written as K9Y3{oB,12Within the corrugated silicate sheets, six-, eight- and twelve-membered rings can be identified (Fig. 2). The vertex symbols for the [SiO4] tetrahedra are as follows: 6.8.12 (for Si2, Si3, Si4 and Si6) and 6.12 (for Si1 and Si5). A schematic representation of the arrangement of the rings within a single layer is given in Fig. 2. Charge balance in the structure is achieved by the incorporation of K+ and Y3+ cations as well as additional F- anions. Y1 resides on an inversion center and is coordinated by six oxygen ligands belonging to six different [SiO4]-tetrahedra (Fig. 3). Within the resulting octahedron, the Y—O bond lengths range from 2.237 (4) - 2.256 (4) Å. Y2 is also octahedrally coordinated (Fig. 4). However, each two adjacent [Y2O6]-octahedra form dimers by sharing one common edge (Fig. 6). Therefore, the spread in the Y—O bond lengths is more siginificant (2.211 (4) - 2.345 (4) Å) which is also reflected in higher values for the distortion parameters: λ = 1.046 and σ2 = 149.49 (for Y2), and λ = 1.006 and σ2 = 20.88 (for Y1), respectively. The volumes of both octahedra are almost identical: 14.545 Å3 (for Y2) and 14.991 Å3 (for Y1). The coordination numbers of the potassium cations are as follows: K1, K2: 8-coordinate, including one F atom; K3: 7-coordinate, including one F atom; K4: 8-coordinate, including two F atoms; K5: 7-coordinate, only O atoms. A slightly different understanding of the structure can be obtained when anion-centred polyhedra are considered as well for the description. Actually, each F- has four nearest potassium neighbors in form of a tetrahedron. Two symmetry-equivalent tetrahedra are joined by a common corner (K4) into [F2K7]-double tetrahedra with symmetry 1 (Fig. 5). A side view of the whole structure is given in Fig. 7.
Bond valence sum calculations using the parameter sets for the K—O, K—F, Y—O and Si—O bonds given by Brown & Altermatt (1985) resulted in the following values (in v.u.) considering cation—anion interactions up to 3.4 Å: K1: 0.924, K2: 0.957, K3: 0.844, K4: 0.772, K5: 1.057, Y1: 3.242, Y2: 3.087, Si1: 4.264, Si2: 4.257, Si3: 4.347, Si4: 4.342, Si5: 4.251, and Si6: 4.326.
The present compound is isostructural with a series of rare earth fluoride silicates: K9(REE)3[Si12O32]F2 (REE: Sm, Eu, Gd; Tang et al., 2008). Chemically related compounds include the following phases: KEu2[Si4O10]F (Jacobsen & Meyer, 1994), Cs2Y[Si4O10]F (Schäfer & Schleid, 2007) and Rb3Sc2[Si4O10]F5 (Schäfer & Schleid, 2011).
Materials which can serve as host structures for luminescent oxosilicates containing trivalent rare earth elements, monovalent alkali cations as well as fluorine anions have been characterized (Jacobsen & Meyer, 1994; Tang et al., 2008; Schäfer & Schleid, 2007, 2011). For structures isotypic to that of the title compound, see: Tang et al. (2008). For general aspects of the crystal chemistry of silicates, see: Liebau (1985). For the definition of distortion parameters, see: Robinson et al. (1971). For bond-valence analysis, see: Brown & Altermatt (1985). For the Inorganic
Database, see: ICSD (2013).Data collection: CrysAlis PRO (Oxford Diffraction, 2006); cell
CrysAlis PRO (Oxford Diffraction, 2006); data reduction: CrysAlis PRO (Oxford Diffraction, 2006); program(s) used to solve structure: SIR2002 (Burla et al., 2003); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ATOMS for Windows (Dowty, 2011); software used to prepare material for publication: publCIF (Westrip, 2010) and WinGX (Farrugia, 2012).F2K9O32Si12Y3 | Z = 1 |
Mr = 1505.71 | F(000) = 730 |
Triclinic, P1 | Dx = 2.886 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 6.8187 (3) Å | Cell parameters from 4373 reflections |
b = 11.3345 (4) Å | θ = 3.0–29.3° |
c = 11.3727 (5) Å | µ = 6.60 mm−1 |
α = 87.846 (3)° | T = 298 K |
β = 89.747 (4)° | Fragment, colourless |
γ = 80.524 (3)° | 0.12 × 0.09 × 0.05 mm |
V = 866.35 (6) Å3 |
Oxford Diffraction Xcalibur diffractometer | 2842 independent reflections |
Graphite monochromator | 2231 reflections with I > 2σ(I) |
Detector resolution: 10.3575 pixels mm-1 | Rint = 0.066 |
ω scans | θmax = 25.4°, θmin = 3.3° |
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2006) | h = −8→8 |
Tmin = 0.801, Tmax = 1 | k = −13→13 |
10508 measured reflections | l = −13→13 |
Refinement on F2 | 0 restraints |
Least-squares matrix: full | Primary atom site location: structure-invariant direct methods |
R[F2 > 2σ(F2)] = 0.039 | Secondary atom site location: difference Fourier map |
wR(F2) = 0.099 | w = 1/[σ2(Fo2) + (0.0515P)2 + 0.2439P] where P = (Fo2 + 2Fc2)/3 |
S = 1.08 | (Δ/σ)max < 0.001 |
2842 reflections | Δρmax = 0.87 e Å−3 |
265 parameters | Δρmin = −0.95 e Å−3 |
F2K9O32Si12Y3 | γ = 80.524 (3)° |
Mr = 1505.71 | V = 866.35 (6) Å3 |
Triclinic, P1 | Z = 1 |
a = 6.8187 (3) Å | Mo Kα radiation |
b = 11.3345 (4) Å | µ = 6.60 mm−1 |
c = 11.3727 (5) Å | T = 298 K |
α = 87.846 (3)° | 0.12 × 0.09 × 0.05 mm |
β = 89.747 (4)° |
Oxford Diffraction Xcalibur diffractometer | 2842 independent reflections |
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2006) | 2231 reflections with I > 2σ(I) |
Tmin = 0.801, Tmax = 1 | Rint = 0.066 |
10508 measured reflections |
R[F2 > 2σ(F2)] = 0.039 | 265 parameters |
wR(F2) = 0.099 | 0 restraints |
S = 1.08 | Δρmax = 0.87 e Å−3 |
2842 reflections | Δρmin = −0.95 e Å−3 |
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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. |
x | y | z | Uiso*/Ueq | ||
K1 | 0.2651 (3) | −0.38667 (12) | 0.01644 (15) | 0.0222 (4) | |
K2 | 0.1715 (2) | −0.19454 (12) | −0.22364 (14) | 0.0184 (4) | |
K3 | 0.1624 (3) | −0.15506 (14) | 0.21410 (15) | 0.0277 (4) | |
K4 | 0.5 | 0 | 0 | 0.0334 (6) | |
K5 | 0.0227 (2) | 0.33078 (11) | 0.51133 (13) | 0.0161 (3) | |
F1 | 0.2472 (7) | −0.1589 (3) | −0.0048 (4) | 0.0256 (10) | |
Y1 | 0 | 0 | 0.5 | 0.0068 (2) | |
Y2 | 0.48856 (9) | 0.48851 (5) | 0.33734 (5) | 0.00691 (17) | |
Si1 | 0.5571 (3) | 0.23257 (13) | 0.51056 (15) | 0.0072 (4) | |
Si2 | 0.3376 (3) | 0.13524 (14) | 0.31036 (16) | 0.0077 (4) | |
Si3 | 0.6564 (3) | −0.09115 (13) | 0.30291 (15) | 0.0071 (4) | |
Si4 | 0.6897 (3) | −0.30506 (13) | 0.15893 (16) | 0.0076 (4) | |
Si5 | −0.0138 (3) | −0.51249 (14) | 0.25833 (15) | 0.0077 (4) | |
Si6 | 0.2872 (3) | −0.66727 (14) | 0.12015 (16) | 0.0079 (4) | |
O1 | 0.5290 (7) | 0.3756 (3) | 0.5151 (4) | 0.0115 (10) | |
O2 | 0.4907 (6) | 0.2083 (3) | 0.3742 (4) | 0.0113 (10) | |
O3 | 0.3903 (6) | 0.1857 (3) | 0.5954 (4) | 0.0097 (9) | |
O4 | 0.7743 (6) | 0.1627 (3) | 0.5395 (4) | 0.0107 (10) | |
O5 | 0.1448 (7) | 0.1240 (3) | 0.3837 (4) | 0.0125 (10) | |
O6 | 0.2791 (7) | 0.2030 (3) | 0.1831 (4) | 0.0129 (10) | |
O7 | 0.4575 (7) | 0.0054 (3) | 0.2739 (4) | 0.0132 (10) | |
O8 | 0.6920 (7) | −0.1638 (3) | 0.1818 (4) | 0.0102 (10) | |
O9 | 0.8444 (7) | −0.0336 (3) | 0.3338 (4) | 0.0114 (10) | |
O10 | 0.9033 (7) | −0.3743 (3) | 0.2102 (4) | 0.0139 (10) | |
O11 | 0.6983 (7) | −0.3156 (3) | 0.0189 (4) | 0.0169 (11) | |
O12 | 0.5030 (7) | −0.3527 (3) | 0.2148 (4) | 0.0123 (10) | |
O13 | 0.1635 (7) | −0.5084 (3) | 0.3462 (4) | 0.0114 (10) | |
O14 | −0.1887 (6) | −0.5722 (3) | 0.3149 (4) | 0.0121 (10) | |
O15 | 0.0686 (7) | −0.5849 (3) | 0.1393 (4) | 0.0131 (10) | |
O16 | 0.4610 (7) | −0.6045 (3) | 0.1658 (4) | 0.0123 (10) |
U11 | U22 | U33 | U12 | U13 | U23 | |
K1 | 0.0222 (9) | 0.0215 (8) | 0.0233 (10) | −0.0056 (6) | 0.0004 (7) | 0.0030 (6) |
K2 | 0.0165 (9) | 0.0192 (7) | 0.0197 (9) | −0.0036 (6) | 0.0005 (7) | 0.0013 (6) |
K3 | 0.0204 (10) | 0.0421 (10) | 0.0197 (9) | −0.0011 (7) | 0.0057 (8) | −0.0068 (7) |
K4 | 0.0395 (17) | 0.0363 (13) | 0.0280 (15) | −0.0195 (11) | −0.0105 (12) | 0.0117 (10) |
K5 | 0.0190 (9) | 0.0132 (7) | 0.0158 (9) | −0.0020 (6) | 0.0035 (7) | −0.0012 (5) |
F1 | 0.030 (3) | 0.026 (2) | 0.022 (2) | −0.0079 (18) | 0.004 (2) | −0.0013 (17) |
Y1 | 0.0038 (5) | 0.0078 (4) | 0.0086 (5) | −0.0007 (3) | 0.0021 (4) | −0.0001 (3) |
Y2 | 0.0032 (3) | 0.0093 (3) | 0.0082 (3) | −0.0010 (2) | 0.0010 (2) | 0.0001 (2) |
Si1 | 0.0056 (10) | 0.0072 (8) | 0.0087 (10) | −0.0010 (6) | 0.0009 (7) | 0.0006 (6) |
Si2 | 0.0053 (10) | 0.0080 (8) | 0.0099 (9) | −0.0017 (6) | 0.0002 (7) | −0.0003 (6) |
Si3 | 0.0038 (9) | 0.0078 (8) | 0.0101 (10) | −0.0015 (6) | 0.0015 (7) | −0.0010 (6) |
Si4 | 0.0064 (10) | 0.0076 (8) | 0.0089 (9) | −0.0012 (6) | 0.0010 (7) | −0.0011 (6) |
Si5 | 0.0035 (9) | 0.0104 (8) | 0.0087 (9) | 0.0002 (6) | 0.0009 (7) | −0.0005 (6) |
Si6 | 0.0072 (10) | 0.0084 (8) | 0.0081 (10) | −0.0014 (6) | 0.0014 (7) | −0.0006 (6) |
O1 | 0.017 (3) | 0.006 (2) | 0.011 (3) | −0.0005 (17) | 0.002 (2) | −0.0002 (16) |
O2 | 0.008 (3) | 0.014 (2) | 0.014 (3) | −0.0057 (17) | −0.001 (2) | −0.0002 (17) |
O3 | 0.009 (3) | 0.012 (2) | 0.008 (2) | −0.0029 (17) | 0.0027 (19) | −0.0004 (17) |
O4 | 0.005 (2) | 0.016 (2) | 0.011 (3) | −0.0002 (17) | 0.0034 (19) | 0.0001 (17) |
O5 | 0.010 (3) | 0.013 (2) | 0.016 (3) | −0.0037 (17) | 0.000 (2) | −0.0016 (17) |
O6 | 0.018 (3) | 0.012 (2) | 0.010 (3) | −0.0063 (18) | 0.001 (2) | 0.0035 (17) |
O7 | 0.008 (3) | 0.009 (2) | 0.021 (3) | 0.0039 (17) | −0.001 (2) | −0.0031 (18) |
O8 | 0.015 (3) | 0.007 (2) | 0.008 (2) | −0.0011 (17) | 0.003 (2) | 0.0002 (16) |
O9 | 0.008 (3) | 0.016 (2) | 0.011 (3) | −0.0053 (18) | −0.0006 (19) | 0.0005 (17) |
O10 | 0.004 (2) | 0.012 (2) | 0.025 (3) | −0.0003 (17) | −0.003 (2) | 0.0032 (18) |
O11 | 0.022 (3) | 0.014 (2) | 0.015 (3) | −0.0024 (19) | 0.004 (2) | −0.0052 (18) |
O12 | 0.009 (3) | 0.010 (2) | 0.017 (3) | −0.0022 (17) | 0.004 (2) | 0.0013 (17) |
O13 | 0.006 (2) | 0.017 (2) | 0.011 (3) | −0.0028 (17) | 0.002 (2) | 0.0005 (17) |
O14 | 0.004 (2) | 0.013 (2) | 0.019 (3) | −0.0020 (17) | −0.001 (2) | 0.0021 (18) |
O15 | 0.007 (3) | 0.018 (2) | 0.013 (3) | 0.0015 (18) | 0.002 (2) | −0.0040 (18) |
O16 | 0.006 (3) | 0.017 (2) | 0.015 (3) | −0.0054 (17) | 0.003 (2) | −0.0045 (17) |
K1—F1 | 2.567 (4) | Si1—O3 | 1.631 (5) |
K1—O16i | 2.778 (5) | Si1—O2 | 1.662 (5) |
K1—O12 | 2.858 (5) | Si2—O5 | 1.574 (5) |
K1—O15ii | 2.956 (5) | Si2—O2 | 1.625 (4) |
K1—O16 | 3.064 (5) | Si2—O7 | 1.629 (4) |
K1—O15 | 3.088 (5) | Si2—O6 | 1.633 (5) |
K1—O11 | 3.188 (5) | Si3—O9 | 1.578 (4) |
K1—O10iii | 3.289 (5) | Si3—O3vi | 1.613 (4) |
K1—O11i | 3.382 (4) | Si3—O7 | 1.623 (4) |
K2—F1 | 2.604 (4) | Si3—O8 | 1.628 (4) |
K2—O9iv | 2.816 (4) | Si4—O12 | 1.584 (5) |
K2—O5v | 2.821 (5) | Si4—O11 | 1.602 (5) |
K2—O2iv | 2.851 (5) | Si4—O10 | 1.635 (5) |
K2—O14ii | 2.861 (4) | Si4—O8 | 1.635 (4) |
K2—O6v | 3.121 (5) | Si5—O13 | 1.579 (5) |
K2—O16i | 3.150 (5) | Si5—O14 | 1.588 (4) |
K2—O15ii | 3.317 (4) | Si5—O10iii | 1.649 (4) |
K3—F1 | 2.554 (5) | Si5—O15 | 1.657 (5) |
K3—O9iii | 2.754 (5) | Si6—O16 | 1.578 (4) |
K3—O4vi | 2.833 (5) | Si6—O11i | 1.601 (5) |
K3—O12 | 2.949 (5) | Si6—O6xi | 1.620 (4) |
K3—O7 | 3.021 (4) | Si6—O15 | 1.642 (5) |
K3—O8iii | 3.248 (5) | O1—Y2x | 2.310 (4) |
K3—O10iii | 3.279 (4) | O1—K5xii | 3.321 (5) |
K4—F1iv | 2.692 (4) | O2—K2iv | 2.851 (5) |
K4—F1 | 2.692 (4) | O3—Si3vi | 1.613 (4) |
K4—O8iv | 2.893 (4) | O4—Y1xii | 2.256 (4) |
K4—O8 | 2.893 (4) | O4—K5xii | 2.759 (4) |
K4—O7 | 3.129 (5) | O4—K3vi | 2.833 (5) |
K4—O7iv | 3.129 (5) | O5—K2v | 2.821 (5) |
K4—O6iv | 3.330 (4) | O6—Si6vii | 1.620 (4) |
K4—O6 | 3.330 (4) | O6—K2v | 3.121 (5) |
K5—O14vii | 2.756 (5) | O8—K3xii | 3.248 (5) |
K5—O4iii | 2.759 (4) | O9—Y1xii | 2.247 (4) |
K5—O13viii | 2.771 (4) | O9—K3xii | 2.754 (5) |
K5—O5 | 2.810 (4) | O9—K2iv | 2.816 (4) |
K5—O13vii | 2.842 (5) | O10—Si5xii | 1.649 (4) |
K5—O3 | 2.907 (5) | O10—K5vi | 3.277 (5) |
K5—O10vi | 3.277 (5) | O10—K3xii | 3.279 (4) |
K5—O1iii | 3.321 (5) | O10—K1xii | 3.289 (5) |
Y1—O5 | 2.237 (4) | O11—Si6i | 1.601 (5) |
Y1—O5viii | 2.237 (4) | O11—K1i | 3.382 (4) |
Y1—O9vi | 2.247 (4) | O12—Y2xi | 2.250 (4) |
Y1—O9iii | 2.247 (4) | O13—Y2xi | 2.213 (4) |
Y1—O4vi | 2.256 (4) | O13—K5viii | 2.771 (4) |
Y1—O4iii | 2.256 (4) | O13—K5xi | 2.842 (5) |
Y2—O14ix | 2.211 (4) | O14—Y2xiii | 2.211 (4) |
Y2—O13vii | 2.213 (4) | O14—K5xi | 2.756 (5) |
Y2—O12vii | 2.250 (4) | O14—K2ii | 2.861 (4) |
Y2—O16vii | 2.275 (4) | O15—K1ii | 2.956 (5) |
Y2—O1x | 2.310 (4) | O15—K2ii | 3.317 (4) |
Y2—O1 | 2.345 (4) | O16—Y2xi | 2.275 (4) |
Si1—O4 | 1.590 (5) | O16—K1i | 2.778 (5) |
Si1—O1 | 1.603 (4) | O16—K2i | 3.150 (5) |
O5—Y1—O5viii | 180 | O5—Si2—O7 | 112.2 (2) |
O5—Y1—O9vi | 96.02 (15) | O2—Si2—O7 | 109.0 (2) |
O5viii—Y1—O9vi | 83.98 (15) | O5—Si2—O6 | 110.5 (3) |
O5—Y1—O9iii | 83.98 (15) | O2—Si2—O6 | 107.2 (2) |
O5viii—Y1—O9iii | 96.02 (15) | O7—Si2—O6 | 102.9 (2) |
O9vi—Y1—O9iii | 180 | O9—Si3—O3vi | 111.7 (2) |
O5—Y1—O4vi | 94.15 (15) | O9—Si3—O7 | 114.3 (2) |
O5viii—Y1—O4vi | 85.85 (15) | O3vi—Si3—O7 | 109.8 (2) |
O9vi—Y1—O4vi | 93.05 (15) | O9—Si3—O8 | 110.7 (2) |
O9iii—Y1—O4vi | 86.95 (15) | O3vi—Si3—O8 | 106.9 (2) |
O5—Y1—O4iii | 85.85 (15) | O7—Si3—O8 | 102.9 (2) |
O5viii—Y1—O4iii | 94.15 (15) | O12—Si4—O11 | 112.3 (3) |
O9vi—Y1—O4iii | 86.95 (15) | O12—Si4—O10 | 114.1 (2) |
O9iii—Y1—O4iii | 93.05 (15) | O11—Si4—O10 | 106.7 (3) |
O4vi—Y1—O4iii | 180.0000 (10) | O12—Si4—O8 | 113.3 (2) |
O14ix—Y2—O13vii | 162.32 (14) | O11—Si4—O8 | 105.2 (2) |
O14ix—Y2—O12vii | 90.23 (16) | O10—Si4—O8 | 104.5 (2) |
O13vii—Y2—O12vii | 100.81 (16) | O13—Si5—O14 | 113.5 (2) |
O14ix—Y2—O16vii | 84.41 (16) | O13—Si5—O10iii | 107.8 (2) |
O13vii—Y2—O16vii | 83.37 (16) | O14—Si5—O10iii | 110.8 (2) |
O12vii—Y2—O16vii | 82.65 (15) | O13—Si5—O15 | 110.3 (2) |
O14ix—Y2—O1x | 103.85 (16) | O14—Si5—O15 | 109.2 (2) |
O13vii—Y2—O1x | 90.94 (16) | O10iii—Si5—O15 | 104.9 (2) |
O12vii—Y2—O1x | 85.09 (15) | O16—Si6—O11i | 111.4 (3) |
O16vii—Y2—O1x | 165.26 (15) | O16—Si6—O6xi | 114.0 (2) |
O14ix—Y2—O1 | 84.94 (16) | O11i—Si6—O6xi | 107.7 (2) |
O13vii—Y2—O1 | 90.07 (16) | O16—Si6—O15 | 111.7 (2) |
O12vii—Y2—O1 | 156.35 (15) | O11i—Si6—O15 | 104.5 (2) |
O16vii—Y2—O1 | 119.73 (14) | O6xi—Si6—O15 | 106.9 (2) |
O1x—Y2—O1 | 73.70 (14) | Si2—O2—Si1 | 137.7 (3) |
O4—Si1—O1 | 115.9 (2) | Si3vi—O3—Si1 | 147.0 (3) |
O4—Si1—O3 | 111.7 (2) | Si6vii—O6—Si2 | 137.6 (3) |
O1—Si1—O3 | 108.3 (2) | Si3—O7—Si2 | 142.8 (3) |
O4—Si1—O2 | 110.8 (2) | Si3—O8—Si4 | 129.8 (3) |
O1—Si1—O2 | 104.0 (2) | Si4—O10—Si5xii | 134.1 (3) |
O3—Si1—O2 | 105.4 (2) | Si4—O11—Si6i | 177.1 (3) |
O5—Si2—O2 | 114.3 (2) | Si6—O15—Si5 | 127.5 (3) |
Symmetry codes: (i) −x+1, −y−1, −z; (ii) −x, −y−1, −z; (iii) x−1, y, z; (iv) −x+1, −y, −z; (v) −x, −y, −z; (vi) −x+1, −y, −z+1; (vii) x, y+1, z; (viii) −x, −y, −z+1; (ix) x+1, y+1, z; (x) −x+1, −y+1, −z+1; (xi) x, y−1, z; (xii) x+1, y, z; (xiii) x−1, y−1, z. |
Experimental details
Crystal data | |
Chemical formula | F2K9O32Si12Y3 |
Mr | 1505.71 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 298 |
a, b, c (Å) | 6.8187 (3), 11.3345 (4), 11.3727 (5) |
α, β, γ (°) | 87.846 (3), 89.747 (4), 80.524 (3) |
V (Å3) | 866.35 (6) |
Z | 1 |
Radiation type | Mo Kα |
µ (mm−1) | 6.60 |
Crystal size (mm) | 0.12 × 0.09 × 0.05 |
Data collection | |
Diffractometer | Oxford Diffraction Xcalibur |
Absorption correction | Multi-scan (CrysAlis PRO; Oxford Diffraction, 2006) |
Tmin, Tmax | 0.801, 1 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 10508, 2842, 2231 |
Rint | 0.066 |
(sin θ/λ)max (Å−1) | 0.602 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.039, 0.099, 1.08 |
No. of reflections | 2842 |
No. of parameters | 265 |
Δρmax, Δρmin (e Å−3) | 0.87, −0.95 |
Computer programs: CrysAlis PRO (Oxford Diffraction, 2006), SIR2002 (Burla et al., 2003), SHELXL97 (Sheldrick, 2008), ATOMS for Windows (Dowty, 2011), publCIF (Westrip, 2010) and WinGX (Farrugia, 2012).
References
Brown, I. D. & Altermatt, D. (1985). Acta Cryst. B41, 244–247. CrossRef CAS Web of Science IUCr Journals Google Scholar
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Jacobsen, H. & Meyer, G. (1994). Z. Kristallogr. 209, 348–350. CrossRef CAS Web of Science Google Scholar
Liebau, F. (1985). Structural chemistry of silicates, p. 347. Berlin, Heidelberg, New York, Tokyo: Springer. Google Scholar
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Schäfer, M. C. & Schleid, Th. (2007). Z. Anorg. Allg. Chem. 633, 1018–1023. Google Scholar
Schäfer, M. C. & Schleid, Th. (2011). Z. Anorg. Allg. Chem. 637, 1152–1157. Google Scholar
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This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
In the present paper we describe a previously unknown phase of the system KF—Y2O3—SiO2. According to Liebau's classification (1985) the crystal structure of the title compound, K9Y3[Si12O32]F2, belongs to the group of open-branched single-layer silicates. The more detailed crystallochemical formula can be written as K9Y3{oB,12∞}[5Si12O32]F2. A single-layer of silicate tetrahedra expands parallel to (110) and is constructed from the condensation of fünfer single chains (Fig. 1). One discrete chain is running parallel to [001] and has a translation period of 11.3727 (5) Å. Each layer contains secondary (Q2) and tertiary (Q3) SiO4 tetrahedra in the ratio of 1:2 (Fig. 2). The Si—O distances of the six crystallographically independent tetrahedra within the asymmetric unit range from 1.574 (5) to 1.662 (5) Å. As one would expect, the Si—Oterminal bonds are considerably shorter than the distances between Si and the bridging O atoms. The O—Si—O angles show a significant scatter throughout all present polyhedra. Nevertheless, the values are in the expected limits for [SiO4] units (Liebau, 1985). Numerically, the degree of distortion can be expressed by the quadratic elongation λ and the angle variance σ2 (Robinson et al., 1971). For the six tetrahedra, these two parameters vary between 1.003 and 1.005 (for λ) and 8.50 and 20.17 (for σ2) indicating that the deviation from regularity is not very pronounced.
Within the corrugated silicate sheets, six-, eight- and twelve-membered rings can be identified (Fig. 2). The vertex symbols for the [SiO4] tetrahedra are as follows: 6.8.12 (for Si2, Si3, Si4 and Si6) and 6.12 (for Si1 and Si5). A schematic representation of the arrangement of the rings within a single layer is given in Fig. 2. Charge balance in the structure is achieved by the incorporation of K+ and Y3+ cations as well as additional F- anions. Y1 resides on an inversion center and is coordinated by six oxygen ligands belonging to six different [SiO4]-tetrahedra (Fig. 3). Within the resulting octahedron, the Y—O bond lengths range from 2.237 (4) - 2.256 (4) Å. Y2 is also octahedrally coordinated (Fig. 4). However, each two adjacent [Y2O6]-octahedra form dimers by sharing one common edge (Fig. 6). Therefore, the spread in the Y—O bond lengths is more siginificant (2.211 (4) - 2.345 (4) Å) which is also reflected in higher values for the distortion parameters: λ = 1.046 and σ2 = 149.49 (for Y2), and λ = 1.006 and σ2 = 20.88 (for Y1), respectively. The volumes of both octahedra are almost identical: 14.545 Å3 (for Y2) and 14.991 Å3 (for Y1). The coordination numbers of the potassium cations are as follows: K1, K2: 8-coordinate, including one F atom; K3: 7-coordinate, including one F atom; K4: 8-coordinate, including two F atoms; K5: 7-coordinate, only O atoms. A slightly different understanding of the structure can be obtained when anion-centred polyhedra are considered as well for the description. Actually, each F- has four nearest potassium neighbors in form of a tetrahedron. Two symmetry-equivalent tetrahedra are joined by a common corner (K4) into [F2K7]-double tetrahedra with point group symmetry 1 (Fig. 5). A side view of the whole structure is given in Fig. 7.
Bond valence sum calculations using the parameter sets for the K—O, K—F, Y—O and Si—O bonds given by Brown & Altermatt (1985) resulted in the following values (in v.u.) considering cation—anion interactions up to 3.4 Å: K1: 0.924, K2: 0.957, K3: 0.844, K4: 0.772, K5: 1.057, Y1: 3.242, Y2: 3.087, Si1: 4.264, Si2: 4.257, Si3: 4.347, Si4: 4.342, Si5: 4.251, and Si6: 4.326.
The present compound is isostructural with a series of rare earth fluoride silicates: K9(REE)3[Si12O32]F2 (REE: Sm, Eu, Gd; Tang et al., 2008). Chemically related compounds include the following phases: KEu2[Si4O10]F (Jacobsen & Meyer, 1994), Cs2Y[Si4O10]F (Schäfer & Schleid, 2007) and Rb3Sc2[Si4O10]F5 (Schäfer & Schleid, 2011).