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Hydrothermally grown crystals of β-K3NdSi6O15, potassium neodymium silicate, have been studied by single-crystal X-ray methods. Under appropriate conditions, the compound crystallizes in space group Bb21m and has lattice constants a = 14.370 (2), b = 15.518 (2) and c = 14.265 (2) Å. There are 30 atom sites in the asymmetric unit of the basic structure. With eight formula units per unit cell, the calculated density is 2.798 Mg m−3. Refinement was carried out to a residual, wR(F2), of 0.1177 [R(F) = 0.0416] using anisotropic temperature factors for all atoms. The structure is based on (Si2O52−) layers, connected by Nd polyhedra to form a three-dimensional framework. Potassium ion sites, some of which are only partially occupied, are located within channels that run between the silicate layers. The silica–neodymia framework of β-K3NdSi6O15, in particular the linkages formed between the silicate layers and Nd polyhedra, bears some similarities to that of the essentially isocompositional phase α-K3NdSi6O15·2H2O. In both, the silicate layers are corrugated so as to accommodate a simple cubic array of NdO6 octahedra with lattice constant ∼ 7.5 Å. Furthermore, the Si2O5 layers in β-K3NdSi6O15 are topologically identical to those of the mineral sazhinite, Na2HCeSi6O15. Although β-K3NdSi6O15 and sazhinite are not isostructural, the structures of each can be described as slight distortions of a high-symmetry parent structure with space group Pbmm.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108768199015797/bs0008sup1.cif
Contains datablocks global, 1

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108768199015797/bs0008sup2.hkl
Contains datablock hai10

Computing details top

Program(s) used to refine structure: SHELXL (Sheldrick, 1993).

Figures top
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[Figure 11]
(1) top
Crystal data top
K3NdSi6O15Z = 8
Mr = 670.0F(000) = 2520
Orthorhombic, Bb21mDx = 2.798 Mg m3
Hall symbol: B -2 -2bMo Kα radiation, λ = 0.71073 Å
a = 14.370 (2) ÅCell parameters from 22 reflections
b = 15.518 (2) ŵ = 4.31 mm1
c = 14.265 (2) ÅT = 293 K
V = 3181.0 (7) Å30.3 × 0.3 × 0.2 mm
Data collection top
Siemens R3m-V
diffractometer
θmax = 27.5°, θmin = 2.0°
Absorption correction: ψ scan (empirical (using intensity measurements)
?
h = 018
Tmin = 0.057, Tmax = 0.119k = 020
1975 measured reflectionsl = 018
1975 independent reflections69 standard reflections
1974 reflections with I > 2σ intensity decay: min 0.9887, max 1.0353, final 1.0160, mean 1.0137%
Rint = 0
Refinement top
Refinement on F21 restraint
Least-squares matrix: Full-matrix least-squaresw = 1/[σ2Fo2 + (0.0746P)2 + 44.0045P]
where P = [max(Fo2,0) + 2Fc2]/3
R[F2 > 2σ(F2)] = 0.042(Δ/σ)max = 0.177
wR(F2) = 0.117Δρmax = 2.59 e Å3
S = 1.13Δρmin = 1.76 e Å3
1974 reflectionsAbsolute structure: Flack, 1983)
244 parametersAbsolute structure parameter: 0.10 (3)
Crystal data top
K3NdSi6O15V = 3181.0 (7) Å3
Mr = 670.0Z = 8
Orthorhombic, Bb21mMo Kα radiation
a = 14.370 (2) ŵ = 4.31 mm1
b = 15.518 (2) ÅT = 293 K
c = 14.265 (2) Å0.3 × 0.3 × 0.2 mm
Data collection top
Siemens R3m-V
diffractometer
1974 reflections with I > 2σ
Absorption correction: ψ scan (empirical (using intensity measurements)
?
Rint = 0
Tmin = 0.057, Tmax = 0.11969 standard reflections
1975 measured reflections intensity decay: min 0.9887, max 1.0353, final 1.0160, mean 1.0137%
1975 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.042(Δ/σ)max = 0.177
wR(F2) = 0.117Δρmax = 2.59 e Å3
S = 1.13Δρmin = 1.76 e Å3
1974 reflectionsAbsolute structure: Flack, 1983)
244 parametersAbsolute structure parameter: 0.10 (3)
1 restraint
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzBiso*/Beq
Nd(1)0.49154 (3)0.57468 (6)0.76341 (3)
Si(1)0.3846 (2)0.7537 (2)0.6119 (2)
Si(2)0.6157 (2)0.4554 (2)0.6051 (2)
Si(3)0.3352 (2)0.7146 (2)0.8969 (2)
Si(4)0.7796 (2)0.4854 (2)0.7495 (2)
Si(5)0.6511 (2)0.4129 (2)0.8930 (2)
Si(6)0.7284 (2)0.6711 (2)0.7837 (2)
K(1)0.4616 (2)0.3182 (2)0.7854 (3)
K(2)0.5754 (3)0.6302 (4)0
K(3)0.8658 (4)0.4920 (3)0.5000
K(4)0.8725 (3)0.5194 (4)0
K(5)0.5896 (3)0.6691 (3)0.5000
K(6)0.8463 (10)0.3053 (11)0.5000
O(1)0.7874 (5)0.5821 (6)0.7990 (5)
O(2)0.4057 (6)0.8563 (5)0.6299 (6)
O(3)0.3788 (6)0.8116 (5)0.8869 (5)
O(4)0.6974 (7)0.4919 (7)0.6720 (6)
O(5)0.6849 (8)0.4354 (8)0
O(6)0.8790 (6)0.4633 (5)0.7096 (7)
O(7)0.7856 (8)0.7081 (7)0.5000
O(8)0.9570 (6)0.6962 (5)0.8319 (6)
O(9)0.1215 (5)0.6630 (6)0.6951 (6)
O(10)0.8906 (9)0.7351 (9)0
O(11)0.7482 (6)0.4201 (6)0.8321 (6)
O(12)0.4142 (5)0.6453 (5)0.1137 (6)
O(13)0.6607 (8)0.4602 (9)0.5000
O(14)0.5710 (6)0.4750 (5)0.8597 (7)
O(15)0.2239 (6)0.2381 (6)0.8582 (6)
O(16)0.2509 (6)0.2046 (6)0.6766 (6)
O(17)0.5265 (7)0.5127 (6)0.6165 (6)

Experimental details

Crystal data
Chemical formulaK3NdSi6O15
Mr670.0
Crystal system, space groupOrthorhombic, Bb21m
Temperature (K)293
a, b, c (Å)14.370 (2), 15.518 (2), 14.265 (2)
V3)3181.0 (7)
Z8
Radiation typeMo Kα
µ (mm1)4.31
Crystal size (mm)0.3 × 0.3 × 0.2
Data collection
DiffractometerSiemens R3m-V
diffractometer
Absorption correctionψ scan (empirical (using intensity measurements)
Tmin, Tmax0.057, 0.119
No. of measured, independent and
observed (I > 2σ) reflections
1975, 1975, 1974
Rint0
(sin θ/λ)max1)0.650
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.042, 0.117, 1.13
No. of reflections1974
No. of parameters244
No. of restraints1
w = 1/[σ2Fo2 + (0.0746P)2 + 44.0045P]
where P = [max(Fo2,0) + 2Fc2]/3
(Δ/σ)max0.177
Δρmax, Δρmin (e Å3)2.59, 1.76
Absolute structureFlack, 1983)
Absolute structure parameter0.10 (3)

Computer programs: SHELXL (Sheldrick, 1993).

 

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