Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270109009421/lg3008sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270109009421/lg3008Isup2.hkl |
K3(Sc0.875Nb0.125)Nb2O9H1.75 was prepared by hydrothermal synthesis. Powders of Sc2O3 and Nb2O5 in a 2:1 molar ratio were sealed in a silver ampoule with a solution of 20M KOH. The ampoule was placed in a 27 ml Inconel autoclave, heated to 848 K and counter-pressured to 17 000 psi (1 p.s.i. = 6.89 kPa). These conditions were held for 10 d, and after this time the ampoule was opened and the contents washed with deionized water. Single crystals of KNbO3 were the major constituent, and K3(Sc0.875Nb0.125)Nb2O9H1.75 colorless tapering hexagonal rod crystals suitable for single-crystal X-ray diffraction were the minor product. FT–IR: 3313 cm-1 (broad, s OH).
Data collection: CrystalClear (Molecular Structure Corporation & Rigaku, 2006); cell refinement: CrystalClear (Molecular Structure Corporation & Rigaku, 2006); data reduction: CrystalClear (Molecular Structure Corporation & Rigaku, 2006); program(s) used to solve structure: SHELXTL (Version 6.10; Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Version 6.10; Sheldrick, 2008); molecular graphics: Diamond (Brandenburg, 1999); software used to prepare material for publication: SHELXTL (Version 6.10; Sheldrick, 2008).
K3(Sc0.875Nb0.125)Nb2O9H1.75 | Dx = 3.846 Mg m−3 |
Mr = 499.84 | Mo Kα radiation, λ = 0.71073 Å |
Hexagonal, P63/mmc | Cell parameters from 2200 reflections |
Hall symbol: -P 6c 2c | θ = 2.8–25.3° |
a = 5.8416 (15) Å | µ = 4.92 mm−1 |
c = 14.604 (5) Å | T = 298 K |
V = 431.6 (2) Å3 | Tapering Hexagonal Rod, colorless |
Z = 2 | 0.30 × 0.27 × 0.25 mm |
F(000) = 473 |
Rigaku AFC-8S Mercury CCD diffractometer | 178 independent reflections |
Radiation source: sealed tube | 170 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.028 |
Detector resolution: 14.6306 pixels mm-1 | θmax = 25.3°, θmin = 2.8° |
ω scans | h = −7→7 |
Absorption correction: multi-scan (Jacobson, 1998) | k = −7→7 |
Tmin = 0.256, Tmax = 0.298 | l = −17→16 |
3318 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.028 | Hydrogen site location: difference Fourier map |
wR(F2) = 0.081 | H-atom parameters not refined |
S = 1.02 | w = 1/[σ2(Fo2) + (0.053P)2 + 2.9407P] where P = (Fo2 + 2Fc2)/3 |
178 reflections | (Δ/σ)max = 0.006 |
21 parameters | Δρmax = 1.04 e Å−3 |
0 restraints | Δρmin = −0.78 e Å−3 |
K3(Sc0.875Nb0.125)Nb2O9H1.75 | Z = 2 |
Mr = 499.84 | Mo Kα radiation |
Hexagonal, P63/mmc | µ = 4.92 mm−1 |
a = 5.8416 (15) Å | T = 298 K |
c = 14.604 (5) Å | 0.30 × 0.27 × 0.25 mm |
V = 431.6 (2) Å3 |
Rigaku AFC-8S Mercury CCD diffractometer | 178 independent reflections |
Absorption correction: multi-scan (Jacobson, 1998) | 170 reflections with I > 2σ(I) |
Tmin = 0.256, Tmax = 0.298 | Rint = 0.028 |
3318 measured reflections |
R[F2 > 2σ(F2)] = 0.028 | 0 restraints |
wR(F2) = 0.081 | H-atom parameters not refined |
S = 1.02 | Δρmax = 1.04 e Å−3 |
178 reflections | Δρmin = −0.78 e Å−3 |
21 parameters |
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. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Nb2 | 0.3333 | 0.6667 | 0.35759 (5) | 0.0064 (4) | |
O2 | 0.4839 (7) | 0.9679 (13) | 0.2500 | 0.0258 (15) | |
H1 | 0.5700 | 1.1388 | 0.2500 | 0.100* | 0.58 |
K1 | 0.6667 | 1.3333 | 0.41124 (18) | 0.0187 (7) | |
O1 | 0.6608 (7) | 0.8304 (3) | 0.4165 (2) | 0.0133 (9) | |
Sc1 | 1.0000 | 1.0000 | 0.5000 | 0.0097 (6) | 0.88 |
Nb1 | 1.0000 | 1.0000 | 0.5000 | 0.0097 (6) | 0.13 |
K2 | 1.0000 | 1.0000 | 0.2500 | 0.0388 (11) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Nb2 | 0.0060 (5) | 0.0060 (5) | 0.0072 (6) | 0.0030 (2) | 0.000 | 0.000 |
O2 | 0.026 (2) | 0.050 (4) | 0.009 (3) | 0.025 (2) | 0.000 | 0.000 |
K1 | 0.0125 (8) | 0.0125 (8) | 0.0311 (15) | 0.0063 (4) | 0.000 | 0.000 |
O1 | 0.0121 (19) | 0.0141 (15) | 0.0131 (18) | 0.0061 (9) | −0.0034 (14) | −0.0017 (7) |
Sc1 | 0.0091 (7) | 0.0091 (7) | 0.0110 (11) | 0.0045 (4) | 0.000 | 0.000 |
Nb1 | 0.0091 (7) | 0.0091 (7) | 0.0110 (11) | 0.0045 (4) | 0.000 | 0.000 |
K2 | 0.0496 (17) | 0.0496 (17) | 0.0174 (18) | 0.0248 (8) | 0.000 | 0.000 |
Nb2—O1i | 1.867 (3) | K1—O1xiii | 3.012 (4) |
Nb2—O1 | 1.867 (3) | K1—O1iv | 3.012 (4) |
Nb2—O1ii | 1.867 (3) | O1—Sc1 | 2.105 (3) |
Nb2—O2i | 2.189 (5) | O1—K1vi | 2.9220 (8) |
Nb2—O2 | 2.189 (5) | O1—K2 | 2.976 (4) |
Nb2—O2ii | 2.189 (5) | O1—K1iv | 3.012 (4) |
Nb2—Nb2iii | 3.1423 (19) | Sc1—O1xiv | 2.105 (3) |
Nb2—K1iv | 3.376 (3) | Sc1—O1xv | 2.105 (3) |
Nb2—K1 | 3.4625 (11) | Sc1—O1ix | 2.105 (3) |
Nb2—K1v | 3.4625 (11) | Sc1—O1xii | 2.105 (3) |
Nb2—K1vi | 3.4625 (11) | Sc1—O1xvi | 2.105 (3) |
Nb2—K2vii | 3.7207 (9) | Sc1—K1xiv | 3.6132 (13) |
O2—Nb2iii | 2.189 (5) | Sc1—K1vi | 3.6132 (13) |
O2—K2 | 2.9253 (8) | Sc1—K1xvii | 3.6132 (13) |
O2—K2vii | 2.9253 (8) | Sc1—K1iv | 3.6132 (13) |
O2—K1 | 2.994 (5) | Sc1—K1xviii | 3.6132 (13) |
O2—K1iii | 2.994 (5) | K2—O2ix | 2.9253 (8) |
K1—O1 | 2.9220 (8) | K2—O2ii | 2.9253 (8) |
K1—O1viii | 2.9220 (8) | K2—O2xviii | 2.9253 (8) |
K1—O1ix | 2.9220 (8) | K2—O2xv | 2.9253 (8) |
K1—O1x | 2.9220 (8) | K2—O2viii | 2.9253 (8) |
K1—O1i | 2.9220 (8) | K2—O1iii | 2.976 (4) |
K1—O1xi | 2.9220 (8) | K2—O1ix | 2.976 (4) |
K1—O2viii | 2.994 (5) | K2—O1xix | 2.976 (4) |
K1—O2x | 2.994 (5) | K2—O1xv | 2.976 (4) |
K1—O1xii | 3.012 (4) | K2—O1xx | 2.976 (4) |
O1i—Nb2—O1 | 100.45 (14) | Nb2—O1—Sc1 | 172.0 (2) |
O1i—Nb2—O1ii | 100.45 (14) | Nb2—O1—K1 | 89.82 (7) |
O1—Nb2—O1ii | 100.45 (14) | Sc1—O1—K1 | 90.40 (8) |
O1i—Nb2—O2i | 91.26 (12) | Nb2—O1—K1vi | 89.82 (7) |
O1—Nb2—O2i | 161.57 (17) | Sc1—O1—K1vi | 90.40 (8) |
O1ii—Nb2—O2i | 91.26 (13) | K1—O1—K1vi | 176.77 (19) |
O1i—Nb2—O2 | 91.26 (12) | Nb2—O1—K2 | 97.77 (14) |
O1—Nb2—O2 | 91.26 (13) | Sc1—O1—K2 | 90.18 (12) |
O1ii—Nb2—O2 | 161.57 (17) | K1—O1—K2 | 88.43 (9) |
O2i—Nb2—O2 | 74.2 (2) | K1vi—O1—K2 | 88.43 (9) |
O1i—Nb2—O2ii | 161.57 (17) | Nb2—O1—K1iv | 84.08 (13) |
O1—Nb2—O2ii | 91.26 (12) | Sc1—O1—K1iv | 87.97 (12) |
O1ii—Nb2—O2ii | 91.26 (12) | K1—O1—K1iv | 91.58 (9) |
O2i—Nb2—O2ii | 74.2 (2) | K1vi—O1—K1iv | 91.58 (9) |
O2—Nb2—O2ii | 74.2 (2) | K2—O1—K1iv | 178.15 (13) |
O1i—Nb2—Nb2iii | 117.45 (11) | O1—Sc1—O1xiv | 180.000 (1) |
O1—Nb2—Nb2iii | 117.45 (12) | O1—Sc1—O1xv | 89.81 (14) |
O1ii—Nb2—Nb2iii | 117.45 (12) | O1xiv—Sc1—O1xv | 90.19 (14) |
O2i—Nb2—Nb2iii | 44.12 (13) | O1—Sc1—O1ix | 89.81 (14) |
O2—Nb2—Nb2iii | 44.12 (13) | O1xiv—Sc1—O1ix | 90.19 (14) |
O2ii—Nb2—Nb2iii | 44.12 (13) | O1xv—Sc1—O1ix | 89.81 (14) |
O1i—Nb2—K1iv | 62.55 (11) | O1—Sc1—O1xii | 90.19 (14) |
O1—Nb2—K1iv | 62.55 (12) | O1xiv—Sc1—O1xii | 89.81 (14) |
O1ii—Nb2—K1iv | 62.55 (12) | O1xv—Sc1—O1xii | 180.0 |
O2i—Nb2—K1iv | 135.88 (13) | O1ix—Sc1—O1xii | 90.19 (14) |
O2—Nb2—K1iv | 135.88 (13) | O1—Sc1—O1xvi | 90.19 (14) |
O2ii—Nb2—K1iv | 135.88 (13) | O1xiv—Sc1—O1xvi | 89.81 (14) |
Nb2iii—Nb2—K1iv | 180.0 | O1xv—Sc1—O1xvi | 90.19 (14) |
O1i—Nb2—K1 | 57.55 (2) | O1ix—Sc1—O1xvi | 180.0 |
O1—Nb2—K1 | 57.55 (2) | O1xii—Sc1—O1xvi | 89.81 (14) |
O1ii—Nb2—K1 | 139.47 (12) | O1—Sc1—K1 | 53.967 (19) |
O2i—Nb2—K1 | 120.10 (4) | O1xiv—Sc1—K1 | 126.03 (2) |
O2—Nb2—K1 | 58.95 (14) | O1xv—Sc1—K1 | 123.58 (10) |
O2ii—Nb2—K1 | 120.10 (4) | O1ix—Sc1—K1 | 53.967 (19) |
Nb2iii—Nb2—K1 | 103.08 (5) | O1xii—Sc1—K1 | 56.42 (10) |
K1iv—Nb2—K1 | 76.92 (5) | O1xvi—Sc1—K1 | 126.03 (2) |
O1i—Nb2—K1v | 57.55 (2) | O1—Sc1—K1xiv | 126.03 (2) |
O1—Nb2—K1v | 139.47 (12) | O1xiv—Sc1—K1xiv | 53.967 (19) |
O1ii—Nb2—K1v | 57.55 (2) | O1xv—Sc1—K1xiv | 56.42 (10) |
O2i—Nb2—K1v | 58.95 (14) | O1ix—Sc1—K1xiv | 126.03 (2) |
O2—Nb2—K1v | 120.10 (4) | O1xii—Sc1—K1xiv | 123.58 (10) |
O2ii—Nb2—K1v | 120.10 (4) | O1xvi—Sc1—K1xiv | 53.967 (19) |
Nb2iii—Nb2—K1v | 103.08 (5) | K1—Sc1—K1xiv | 180.00 (8) |
K1iv—Nb2—K1v | 76.92 (5) | O1—Sc1—K1vi | 53.97 (2) |
K1—Nb2—K1v | 115.04 (3) | O1xiv—Sc1—K1vi | 126.033 (19) |
O1i—Nb2—K1vi | 139.47 (12) | O1xv—Sc1—K1vi | 53.97 (2) |
O1—Nb2—K1vi | 57.55 (2) | O1ix—Sc1—K1vi | 123.58 (10) |
O1ii—Nb2—K1vi | 57.55 (2) | O1xii—Sc1—K1vi | 126.03 (2) |
O2i—Nb2—K1vi | 120.10 (4) | O1xvi—Sc1—K1vi | 56.42 (10) |
O2—Nb2—K1vi | 120.10 (4) | K1—Sc1—K1vi | 107.88 (4) |
O2ii—Nb2—K1vi | 58.95 (13) | K1xiv—Sc1—K1vi | 72.12 (4) |
Nb2iii—Nb2—K1vi | 103.08 (5) | O1—Sc1—K1xvii | 126.033 (19) |
K1iv—Nb2—K1vi | 76.92 (5) | O1xiv—Sc1—K1xvii | 53.97 (2) |
K1—Nb2—K1vi | 115.04 (3) | O1xv—Sc1—K1xvii | 126.03 (2) |
K1v—Nb2—K1vi | 115.04 (3) | O1ix—Sc1—K1xvii | 56.42 (10) |
O1i—Nb2—K2vii | 52.42 (11) | O1xii—Sc1—K1xvii | 53.97 (2) |
O1—Nb2—K2vii | 126.64 (2) | O1xvi—Sc1—K1xvii | 123.58 (10) |
O1ii—Nb2—K2vii | 126.64 (2) | K1—Sc1—K1xvii | 72.12 (4) |
O2i—Nb2—K2vii | 51.781 (10) | K1xiv—Sc1—K1xvii | 107.88 (4) |
O2—Nb2—K2vii | 51.781 (10) | K1vi—Sc1—K1xvii | 180.0 |
O2ii—Nb2—K2vii | 109.15 (13) | O1—Sc1—K1iv | 56.42 (10) |
Nb2iii—Nb2—K2vii | 65.021 (15) | O1xiv—Sc1—K1iv | 123.58 (10) |
K1iv—Nb2—K2vii | 114.979 (15) | O1xv—Sc1—K1iv | 126.03 (2) |
K1—Nb2—K2vii | 69.76 (2) | O1ix—Sc1—K1iv | 126.03 (2) |
K1v—Nb2—K2vii | 69.76 (2) | O1xii—Sc1—K1iv | 53.97 (2) |
K1vi—Nb2—K2vii | 168.10 (5) | O1xvi—Sc1—K1iv | 53.97 (2) |
Nb2iii—O2—Nb2 | 91.8 (3) | K1—Sc1—K1iv | 72.12 (4) |
Nb2iii—O2—K2 | 92.22 (9) | K1xiv—Sc1—K1iv | 107.88 (4) |
Nb2—O2—K2 | 92.22 (9) | K1vi—Sc1—K1iv | 72.12 (4) |
Nb2iii—O2—K2vii | 92.22 (9) | K1xvii—Sc1—K1iv | 107.88 (4) |
Nb2—O2—K2vii | 92.22 (9) | O1—Sc1—K1xviii | 123.58 (10) |
K2—O2—K2vii | 173.6 (3) | O1xiv—Sc1—K1xviii | 56.42 (10) |
Nb2iii—O2—K1 | 174.0 (2) | O1xv—Sc1—K1xviii | 53.97 (2) |
Nb2—O2—K1 | 82.26 (5) | O1ix—Sc1—K1xviii | 53.97 (2) |
K2—O2—K1 | 88.03 (9) | O1xii—Sc1—K1xviii | 126.03 (2) |
K2vii—O2—K1 | 88.03 (9) | O1xvi—Sc1—K1xviii | 126.03 (2) |
Nb2iii—O2—K1iii | 82.26 (5) | K1—Sc1—K1xviii | 107.88 (4) |
Nb2—O2—K1iii | 174.0 (2) | K1xiv—Sc1—K1xviii | 72.12 (4) |
K2—O2—K1iii | 88.03 (9) | K1vi—Sc1—K1xviii | 107.88 (4) |
K2vii—O2—K1iii | 88.03 (9) | K1xvii—Sc1—K1xviii | 72.12 (4) |
K1—O2—K1iii | 103.7 (2) | K1iv—Sc1—K1xviii | 180.0 |
O1—K1—O1viii | 119.932 (9) | O2ix—K2—O2ii | 173.6 (3) |
O1—K1—O1ix | 61.15 (13) | O2ix—K2—O2xviii | 66.4 (3) |
O1viii—K1—O1ix | 58.81 (13) | O2ii—K2—O2xviii | 120.000 (1) |
O1—K1—O1x | 119.931 (10) | O2ix—K2—O2 | 120.0 |
O1viii—K1—O1x | 119.931 (9) | O2ii—K2—O2 | 53.6 (3) |
O1ix—K1—O1x | 176.77 (19) | O2xviii—K2—O2 | 173.6 (3) |
O1—K1—O1i | 58.81 (13) | O2ix—K2—O2xv | 120.000 (2) |
O1viii—K1—O1i | 176.77 (18) | O2ii—K2—O2xv | 66.4 (3) |
O1ix—K1—O1i | 119.931 (9) | O2xviii—K2—O2xv | 53.6 (3) |
O1x—K1—O1i | 61.15 (14) | O2—K2—O2xv | 120.000 (2) |
O1—K1—O1xi | 176.77 (18) | O2ix—K2—O2viii | 53.6 (3) |
O1viii—K1—O1xi | 61.15 (13) | O2ii—K2—O2viii | 120.000 (1) |
O1ix—K1—O1xi | 119.931 (10) | O2xviii—K2—O2viii | 120.0 |
O1x—K1—O1xi | 58.81 (13) | O2—K2—O2viii | 66.4 (3) |
O1i—K1—O1xi | 119.931 (9) | O2xv—K2—O2viii | 173.6 (3) |
O1—K1—O2 | 58.86 (11) | O2ix—K2—O1iii | 118.86 (7) |
O1viii—K1—O2 | 123.51 (14) | O2ii—K2—O1iii | 59.03 (7) |
O1ix—K1—O2 | 91.55 (9) | O2xviii—K2—O1iii | 118.86 (7) |
O1x—K1—O2 | 91.55 (9) | O2—K2—O1iii | 59.03 (7) |
O1i—K1—O2 | 58.86 (11) | O2xv—K2—O1iii | 91.84 (8) |
O1xi—K1—O2 | 123.51 (13) | O2viii—K2—O1iii | 91.84 (8) |
O1—K1—O2viii | 91.55 (9) | O2ix—K2—O1ix | 59.03 (7) |
O1viii—K1—O2viii | 58.86 (12) | O2ii—K2—O1ix | 118.86 (7) |
O1ix—K1—O2viii | 58.86 (11) | O2xviii—K2—O1ix | 91.84 (8) |
O1x—K1—O2viii | 123.51 (13) | O2—K2—O1ix | 91.84 (8) |
O1i—K1—O2viii | 123.51 (14) | O2xv—K2—O1ix | 118.86 (7) |
O1xi—K1—O2viii | 91.55 (9) | O2viii—K2—O1ix | 59.03 (7) |
O2—K1—O2viii | 64.66 (17) | O1iii—K2—O1ix | 146.49 (6) |
O1—K1—O2x | 123.51 (14) | O2ix—K2—O1xix | 91.84 (8) |
O1viii—K1—O2x | 91.55 (9) | O2ii—K2—O1xix | 91.84 (8) |
O1ix—K1—O2x | 123.51 (14) | O2xviii—K2—O1xix | 59.03 (7) |
O1x—K1—O2x | 58.86 (11) | O2—K2—O1xix | 118.86 (7) |
O1i—K1—O2x | 91.55 (9) | O2xv—K2—O1xix | 59.03 (7) |
O1xi—K1—O2x | 58.86 (11) | O2viii—K2—O1xix | 118.86 (7) |
O2—K1—O2x | 64.66 (17) | O1iii—K2—O1xix | 59.92 (11) |
O2viii—K1—O2x | 64.66 (17) | O1ix—K2—O1xix | 146.49 (6) |
O1—K1—O1xii | 60.31 (12) | O2ix—K2—O1xv | 91.84 (8) |
O1viii—K1—O1xii | 88.42 (9) | O2ii—K2—O1xv | 91.84 (8) |
O1ix—K1—O1xii | 60.31 (12) | O2xviii—K2—O1xv | 59.03 (7) |
O1x—K1—O1xii | 117.19 (9) | O2—K2—O1xv | 118.86 (7) |
O1i—K1—O1xii | 88.42 (9) | O2xv—K2—O1xv | 59.03 (7) |
O1xi—K1—O1xii | 117.19 (9) | O2viii—K2—O1xv | 118.86 (7) |
O2—K1—O1xii | 119.15 (10) | O1iii—K2—O1xv | 146.49 (6) |
O2viii—K1—O1xii | 119.15 (10) | O1ix—K2—O1xv | 59.92 (11) |
O2x—K1—O1xii | 175.23 (13) | O1xix—K2—O1xv | 109.57 (13) |
O1—K1—O1xiii | 117.19 (9) | O2ix—K2—O1xx | 59.03 (7) |
O1viii—K1—O1xiii | 60.31 (12) | O2ii—K2—O1xx | 118.86 (7) |
O1ix—K1—O1xiii | 88.42 (9) | O2xviii—K2—O1xx | 91.84 (8) |
O1x—K1—O1xiii | 88.42 (9) | O2—K2—O1xx | 91.84 (8) |
O1i—K1—O1xiii | 117.19 (9) | O2xv—K2—O1xx | 118.86 (7) |
O1xi—K1—O1xiii | 60.31 (12) | O2viii—K2—O1xx | 59.03 (7) |
O2—K1—O1xiii | 175.23 (13) | O1iii—K2—O1xx | 59.92 (11) |
O2viii—K1—O1xiii | 119.15 (10) | O1ix—K2—O1xx | 109.57 (13) |
O2x—K1—O1xiii | 119.15 (10) | O1xix—K2—O1xx | 59.92 (11) |
O1xii—K1—O1xiii | 56.89 (11) | O1xv—K2—O1xx | 146.49 (6) |
O1—K1—O1iv | 88.42 (9) | O2ix—K2—O1 | 118.86 (7) |
O1viii—K1—O1iv | 117.19 (9) | O2ii—K2—O1 | 59.03 (7) |
O1ix—K1—O1iv | 117.19 (9) | O2xviii—K2—O1 | 118.86 (7) |
O1x—K1—O1iv | 60.31 (12) | O2—K2—O1 | 59.03 (7) |
O1i—K1—O1iv | 60.31 (12) | O2xv—K2—O1 | 91.84 (8) |
O1xi—K1—O1iv | 88.42 (9) | O2viii—K2—O1 | 91.84 (8) |
O2—K1—O1iv | 119.15 (10) | O1iii—K2—O1 | 109.57 (13) |
O2viii—K1—O1iv | 175.23 (13) | O1ix—K2—O1 | 59.92 (11) |
O2x—K1—O1iv | 119.15 (10) | O1xix—K2—O1 | 146.49 (6) |
O1xii—K1—O1iv | 56.89 (11) | O1xv—K2—O1 | 59.92 (11) |
O1xiii—K1—O1iv | 56.89 (11) | O1xx—K2—O1 | 146.49 (6) |
Symmetry codes: (i) −y+1, x−y+1, z; (ii) −x+y, −x+1, z; (iii) x, y, −z+1/2; (iv) −x+1, −y+2, −z+1; (v) x−1, y−1, z; (vi) x, y−1, z; (vii) x−1, y, z; (viii) −y+2, x−y+2, z; (ix) −x+y+1, −x+2, z; (x) −x+y, −x+2, z; (xi) x, y+1, z; (xii) y, −x+y+1, −z+1; (xiii) x−y+1, x+1, −z+1; (xiv) −x+2, −y+2, −z+1; (xv) −y+2, x−y+1, z; (xvi) x−y+1, x, −z+1; (xvii) −x+2, −y+3, −z+1; (xviii) x+1, y, z; (xix) −y+2, x−y+1, −z+1/2; (xx) −x+y+1, −x+2, −z+1/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H1···O2x | 0.86 | 2.49 | 3.1981 (13) | 140 |
O2—H1···O2viii | 0.86 | 2.49 | 3.1981 (13) | 140 |
Symmetry codes: (viii) −y+2, x−y+2, z; (x) −x+y, −x+2, z. |
Experimental details
Crystal data | |
Chemical formula | K3(Sc0.875Nb0.125)Nb2O9H1.75 |
Mr | 499.84 |
Crystal system, space group | Hexagonal, P63/mmc |
Temperature (K) | 298 |
a, c (Å) | 5.8416 (15), 14.604 (5) |
V (Å3) | 431.6 (2) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 4.92 |
Crystal size (mm) | 0.30 × 0.27 × 0.25 |
Data collection | |
Diffractometer | Rigaku AFC-8S Mercury CCD diffractometer |
Absorption correction | Multi-scan (Jacobson, 1998) |
Tmin, Tmax | 0.256, 0.298 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3318, 178, 170 |
Rint | 0.028 |
(sin θ/λ)max (Å−1) | 0.602 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.028, 0.081, 1.02 |
No. of reflections | 178 |
No. of parameters | 21 |
H-atom treatment | H-atom parameters not refined |
Δρmax, Δρmin (e Å−3) | 1.04, −0.78 |
Computer programs: CrystalClear (Molecular Structure Corporation & Rigaku, 2006), SHELXTL (Version 6.10; Sheldrick, 2008), Diamond (Brandenburg, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H1···O2i | 0.86 | 2.49 | 3.1981 (13) | 140 |
O2—H1···O2ii | 0.86 | 2.49 | 3.1981 (13) | 140 |
Symmetry codes: (i) −x+y, −x+2, z; (ii) −y+2, x−y+2, z. |
Refractory oxides such as Sc2O3, Y2O3, ZrO2, HfO2 and Ta2O5 have been a source of much interest over the years owing to their many practical uses, including applications as high-temperature liners, abrasives and laser hosts. In the process of developing these materials, there were preliminary explorations of refractory mixed metal oxides. Because of the difficulty of making high quality samples of the extremely refractory compounds, and particularly as single crystals, investigation of these metal oxides has been somewhat neglected.
One relatively unexplored system is that of the scandium niobates, which have generally been limited to powders created by conventional solid state methods (Rooksby & White, 1963, 1964). Only in one case was single-crystal growth of ScNbO4 (Ross & Grün, 1990) by chemical vapor deposition reported; however, the crystal size was very small, which prevented complete structural characterization of the material. Hydrothermal solutions have demonstrated the ability to produce single crystals of several classical refractory oxides (Kuznetsov & Sidorenko, 1968). Therefore, a hydrothermal synthesis study of the scandium niobates was undertaken. Using high temperatures, pressures and extremely basic solutions, the title compound was prepared.
The title structure consists of Sc0.875Nb0.125O6 and NbO3(OH)3 octahedral building blocks (Fig. 1). The Sc0.875Nb0.125O6 units are corner sharing via atom O1 with the niobium octahedra. An NbO3(OH)3 octahedron occupies the (110) plane and is face sharing with another niobium octahedron. At 1.867 (3) Å, the three Nb—O1 bonds are much shorter than the 2.189 (5) Å Nb—O2 bonds, distorting the octahedra. This has also been observed in other face-sharing niobium systems (Tyutyunnik et al., 2002; Tarakina et al., 2003). As a result of metal–metal repulsion, the Nb atoms are shifted away from each other. The distortion is compounded by the corner-shared O1 atom bound to the lower valent Sc3+ ion creating the short Nb—O1 bond. This results in an O1—Nb—O1iii bond angle of 100.45 (1)° in contrast to 74.2 (2)° for the O2—Nb—O2iii angle [symmetry code: (iii) -x + y, -x + 1, z]. Contrary to the face-sharing niobates, the Sc0.875Nb0.125O6 octahedra exhibit no distortion. The combined scandium and distorted niobium environments form a framework that extends along the c axis.
A broad IR stretch located at 3313 cm-1 indicates the presence of a hydroxy group. In order to locate the hydrogen site, bond valence sums were calculated. This revealed atom O2 [1.366 valence units (v.u.)] as significantly underbonded compared with atom O1 (2.056 v.u.). Therefore, a site located 0.86 Å from atom O2 was designated H1. This has a bifuricated hydrogen bond to atoms O2i and O2ii [symmetry codes: (i) -x + y, -x + 2, z; (ii) -y + 2, x - y + 2, z] with distances of 2.491 (7) and 2.486 (7) Å, respectively. The H atom was kept fixed with Uiso = 0.10 Å2 and a partial occupancy to provide an electrically neutral formula. Including the hydrogen environment, a recalculation of the bond valence sum for atom O2 provided an acceptable value of 1.975 v.u. Both hydrogen bonds are considered weak (Brown, 1976) because the bond valence attributed to the acceptor O atoms is less than 0.20 valence units. Furthermore, the O2i···O2ii distance is 3.1981 (13) Å. This is much longer than a distance less than or equal to 2.73 Å, which is a requirement of a strong hydrogen bond.
The potassium environments are both 12-coordinate. They have a sixfold coordination of O atoms, which is parallel to the ab plane, with a threefold coordination above and below the plane in the c direction. The coordination environment is created by two different cage enclosures around atoms K1 and K2, seen in Figs. 2 and 3, respectively. The K1 cage is formed by three scandium and four niobium corner-sharing octahedra. They combine to form a cube-like enclosure with one vertex missing. Atom K1 is centrally located in the cage along the (110) plane. The eighth vertex required to complete the cube is occupied by the bifuricated hydrogen bond. The hydrogen bond also contributes to the K2 cage, but is less pronounced in this case. An eight-membered cage composed of two scandium and six niobium octahedra is oriented to construct a trigonal face-bicapped prism with K2 located along the (100) plane. Scandium octahedra form the face-capping pyramid, while the trigonal prism is built of face-sharing niobium octahedra. A similar permethylpolysilane Si8Me14 cage structure has been reported (West & Carberry, 1975). The most notable difference is the tetrahedral coordination of the silicon versus the octahedral scandium and niobium environments. The polysilane cage enclosure is small compared with the large internal volume (5.8 × 5.8 × 7.3 Å) of the scandium/niobium cage structure. This internal volume created by the octahedral environments provides space for the hydrogen-bond network to interact along the ab plane.
The long-range structure (Fig. 4) has alternating sheets of the K1 and K2 cage structures extending along the ab plane. As the K1 sheets propagate in the c direction, they angle themselves as if a mirror plane extends through the middle of the K2 sandwiched sheet. The K2 -6m2 site symmetry causes a 60o rotation from one K2 sheet to the next.