inorganic compounds
Scheelitetype NaDy(WO_{4})_{2}
^{a}Department of Physics and Chemistry, Henan Polytechnic University, Jiaozuo, Henan 454000, People's Republic of China, and ^{b}State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, People's Republic of China
^{*}Correspondence email: iamzd@hpu.edu.cn
The title compound sodium dysprosium(III) bis[tungstate(VI)], NaDy(WO_{4})_{2}, has been synthesized under high temperature solution growth (HTSG) conditions in air. The compound crystallizes with the scheelite structure and is composed of isolated WO_{4} tetrahedra ( symmetry) with one set of bond lengths and distorted [(Na/Dy)O_{8}] dodecahedra ( symmetry; occupancy ratio Na:Dy = 1:1) with two sets of bond lengths.
Related literature
For the structures, properties and applications of alkali rareearth bistungstates with general formula ARE(WO_{4})_{2} (A = alkali metal, RE = rareearth metal), see: Perets et al. (2007); Han et al. (2002); Huang et al. (2006); Li et al. (1990). For the scheelite (CaWO_{4}) structure, see: Sillen & Nylander (1943).
Experimental
Crystal data

Refinement

Data collection: CrystalClear (Rigaku, 2000); cell CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2004); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).
Supporting information
10.1107/S1600536809052271/wm2287sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536809052271/wm2287Isup2.hkl
Single crystal of NaDy(WO_{4})_{2} were prepared by a high temperature solution reaction, using analytical reagents of Dy_{2}O_{3}, Na_{2}CO_{3} and WO_{3} in the molar ratio of Na: Dy: W = 8:1:10. The starting mixture was finely ground in an agate mortar to ensure the best
and reactivity, and then transferred to a platinum crucible to be heated at a temperature of 773 K for 8 h. The sintered product was reground and continuously heated at 1273 K for 20 h, cooled to 673 K at a rate of 4 K/h, and then quenched to room temperature. A few light yellow and prismatically shaped crystals of the title compound were obtained.The Na1 and Dy1 atoms are in a substitutionaltype disorder in the structure. Therefore the atomic position and anisotropic displacement parameters of Na1 and Dy1 atoms were constrained to be identical. In the initial leastsquares
the occupancy factors of Na1 and Dy1 atoms were set to be free. The results show that the occupancy factors were close to 1:1, viz Na1: Dy1 = 0.50273: 0.49727, and were eventually fixed in a 1:1 ratio. The highest peak in the final difference is 1.55 e/Å^{3} from the W1 site, and the deepest hole is 1.40 e/Å^{3} from the Na1/Dy1 site.Data collection: CrystalClear (Rigaku, 2000); cell
CrystalClear (Rigaku, 2000); data reduction: CrystalClear (Rigaku, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2004); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).NaDy(WO_{4})_{2}  D_{x} = 7.186 Mg m^{−}^{3} 
M_{r} = 681.19  Mo Kα radiation, λ = 0.71073 Å 
Tetragonal, I4_{1}/a  Cell parameters from 405 reflections 
Hall symbol: I 4ad  θ = 3.6–27.5° 
a = 5.2545 (5) Å  µ = 48.27 mm^{−}^{1} 
c = 11.4029 (15) Å  T = 298 K 
V = 314.83 (6) Å^{3}  Prism, light yellow 
Z = 2  0.10 × 0.10 × 0.08 mm 
F(000) = 578 
Rigaku Mercury70 diffractometer  181 independent reflections 
Radiation source: finefocus sealed tube  143 reflections with I > 2σ(I) 
Graphite monochromator  R_{int} = 0.053 
Detector resolution: 14.6306 pixels mm^{1}  θ_{max} = 27.5°, θ_{min} = 4.3° 
ω scans  h = −6→6 
Absorption correction: multiscan (SADABS; Bruker, 1997)  k = −6→6 
T_{min} = 0.263, T_{max} = 1.000  l = −14→13 
1128 measured reflections 
Refinement on F^{2}  Primary atom site location: structureinvariant direct methods 
Leastsquares matrix: full  Secondary atom site location: difference Fourier map 
R[F^{2} > 2σ(F^{2})] = 0.024  w = 1/[σ^{2}(F_{o}^{2}) + (0.0045P)^{2}] where P = (F_{o}^{2} + 2F_{c}^{2})/3 
wR(F^{2}) = 0.056  (Δ/σ)_{max} < 0.001 
S = 0.87  Δρ_{max} = 1.55 e Å^{−}^{3} 
181 reflections  Δρ_{min} = −1.40 e Å^{−}^{3} 
15 parameters  Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^{*}=kFc[1+0.001xFc^{2}λ^{3}/sin(2θ)]^{1/4} 
0 restraints  Extinction coefficient: 0.0295 (17) 
NaDy(WO_{4})_{2}  Z = 2 
M_{r} = 681.19  Mo Kα radiation 
Tetragonal, I4_{1}/a  µ = 48.27 mm^{−}^{1} 
a = 5.2545 (5) Å  T = 298 K 
c = 11.4029 (15) Å  0.10 × 0.10 × 0.08 mm 
V = 314.83 (6) Å^{3} 
Rigaku Mercury70 diffractometer  181 independent reflections 
Absorption correction: multiscan (SADABS; Bruker, 1997)  143 reflections with I > 2σ(I) 
T_{min} = 0.263, T_{max} = 1.000  R_{int} = 0.053 
1128 measured reflections 
R[F^{2} > 2σ(F^{2})] = 0.024  15 parameters 
wR(F^{2}) = 0.056  0 restraints 
S = 0.87  Δρ_{max} = 1.55 e Å^{−}^{3} 
181 reflections  Δρ_{min} = −1.40 e Å^{−}^{3} 
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 Rfactor wR and goodness of fit S are based on F^{2}, conventional Rfactors 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 Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. Rfactors 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. 
x  y  z  U_{iso}*/U_{eq}  Occ. (<1)  
Na1  0.5000  −0.2500  0.1250  0.0068 (4)  0.50 
Dy1  0.5000  −0.2500  0.1250  0.0068 (4)  0.50 
W1  0.0000  0.2500  0.1250  0.0091 (4)  
O1  0.2419 (14)  0.0977 (13)  0.0404 (6)  0.0187 (16) 
U^{11}  U^{22}  U^{33}  U^{12}  U^{13}  U^{23}  
Na1  0.0090 (6)  0.0090 (6)  0.0024 (8)  0.000  0.000  0.000 
Dy1  0.0090 (6)  0.0090 (6)  0.0024 (8)  0.000  0.000  0.000 
W1  0.0098 (4)  0.0098 (4)  0.0076 (6)  0.000  0.000  0.000 
O1  0.024 (5)  0.017 (4)  0.015 (3)  0.001 (3)  0.003 (3)  0.001 (3) 
(Na/Dy)1—O1^{i}  2.457 (7)  (Na/Dy)1—O1^{vii}  2.471 (7) 
(Na/Dy)1—O1^{ii}  2.457 (7)  (Na/Dy)1—O1  2.471 (7) 
(Na/Dy)1—O1^{iii}  2.457 (7)  W1—O1^{viii}  1.785 (7) 
(Na/Dy)1—O1^{iv}  2.457 (7)  W1—O1^{ix}  1.785 (7) 
(Na/Dy)1—O1^{v}  2.471 (7)  W1—O1  1.785 (7) 
(Na/Dy)1—O1^{vi}  2.471 (7)  W1—O1^{x}  1.785 (7) 
O1^{i}—(Na/Dy)1—O1^{ii}  79.7 (3)  O1^{vi}—(Na/Dy)1—O1^{vii}  98.76 (12) 
O1^{i}—(Na/Dy)1—O1^{iii}  126.1 (2)  O1^{i}—(Na/Dy)1—O1  68.80 (16) 
O1^{ii}—(Na/Dy)1—O1^{iii}  126.1 (2)  O1^{ii}—(Na/Dy)1—O1  76.3 (3) 
O1^{i}—(Na/Dy)1—O1^{iv}  126.1 (2)  O1^{iii}—(Na/Dy)1—O1  73.31 (14) 
O1^{ii}—(Na/Dy)1—O1^{iv}  126.1 (2)  O1^{iv}—(Na/Dy)1—O1  152.4 (3) 
O1^{iii}—(Na/Dy)1—O1^{iv}  79.7 (3)  O1^{v}—(Na/Dy)1—O1  98.76 (12) 
O1^{i}—(Na/Dy)1—O1^{v}  152.4 (3)  O1^{vi}—(Na/Dy)1—O1  98.76 (12) 
O1^{ii}—(Na/Dy)1—O1^{v}  73.31 (14)  O1^{vii}—(Na/Dy)1—O1  134.1 (3) 
O1^{iii}—(Na/Dy)1—O1^{v}  68.80 (16)  O1^{viii}—W1—O1^{ix}  107.0 (2) 
O1^{iv}—(Na/Dy)1—O1^{v}  76.3 (3)  O1^{viii}—W1—O1  114.6 (4) 
O1^{i}—(Na/Dy)1—O1^{vi}  73.31 (14)  O1^{ix}—W1—O1  107.0 (2) 
O1^{ii}—(Na/Dy)1—O1^{vi}  152.4 (3)  O1^{viii}—W1—O1^{x}  107.0 (2) 
O1^{iii}—(Na/Dy)1—O1^{vi}  76.3 (3)  O1^{ix}—W1—O1^{x}  114.6 (4) 
O1^{iv}—(Na/Dy)1—O1^{vi}  68.80 (16)  O1—W1—O1^{x}  107.0 (2) 
O1^{v}—(Na/Dy)1—O1^{vi}  134.1 (3)  W1—O1—Dy1^{ii}  131.4 (3) 
O1^{i}—(Na/Dy)1—O1^{vii}  76.3 (3)  W1—O1—(Na/Dy)1^{ii}  131.4 (3) 
O1^{ii}—(Na/Dy)1—O1^{vii}  68.80 (16)  W1—O1—(Na/Dy)1  120.8 (3) 
O1^{iii}—(Na/Dy)1—O1^{vii}  152.4 (3)  Dy1^{ii}—O1—(Na/Dy)1  103.7 (3) 
O1^{iv}—(Na/Dy)1—O1^{vii}  73.31 (14)  (Na/Dy)1^{ii}—O1—(Na/Dy)1  103.7 (3) 
O1^{v}—(Na/Dy)1—O1^{vii}  98.76 (12) 
Symmetry codes: (i) x, y−1/2, −z; (ii) −x+1, −y, −z; (iii) y+1/4, −x+1/4, z+1/4; (iv) −y+3/4, x−3/4, z+1/4; (v) y+3/4, −x+1/4, −z+1/4; (vi) −y+1/4, x−3/4, −z+1/4; (vii) −x+1, −y−1/2, z; (viii) −x, −y+1/2, z; (ix) −y+1/4, x+1/4, −z+1/4; (x) y−1/4, −x+1/4, −z+1/4. 
Experimental details
Crystal data  
Chemical formula  NaDy(WO_{4})_{2} 
M_{r}  681.19 
Crystal system, space group  Tetragonal, I4_{1}/a 
Temperature (K)  298 
a, c (Å)  5.2545 (5), 11.4029 (15) 
V (Å^{3})  314.83 (6) 
Z  2 
Radiation type  Mo Kα 
µ (mm^{−}^{1})  48.27 
Crystal size (mm)  0.10 × 0.10 × 0.08 
Data collection  
Diffractometer  Rigaku Mercury70 diffractometer 
Absorption correction  Multiscan (SADABS; Bruker, 1997) 
T_{min}, T_{max}  0.263, 1.000 
No. of measured, independent and observed [I > 2σ(I)] reflections  1128, 181, 143 
R_{int}  0.053 
(sin θ/λ)_{max} (Å^{−}^{1})  0.649 
Refinement  
R[F^{2} > 2σ(F^{2})], wR(F^{2}), S  0.024, 0.056, 0.87 
No. of reflections  181 
No. of parameters  15 
Δρ_{max}, Δρ_{min} (e Å^{−}^{3})  1.55, −1.40 
Computer programs: CrystalClear (Rigaku, 2000), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 2004), SHELXTL (Sheldrick, 2008).
(Na/Dy)1—O1^{i}  2.457 (7)  W1—O1  1.785 (7) 
(Na/Dy)1—O1  2.471 (7) 
Symmetry code: (i) y+1/4, −x+1/4, z+1/4. 
References
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In the past years an increasing interest in the synthesis and characterization of rareearth double tungstate(VI) crystals with general formula ARE(WO_{4})_{2} (A = alkali metal, RE = rareearth metal) has been observed due to their interesting magnetic, electric and optical properties (Perets et al., 2007; Huang et al., 2006; Li et al., 1990; Han et al., 2002). These compounds are attractive solidstate laser host materials because of their large rareearth ion admittance. Most of these crystals have tetragonal symmetry and crystallize with the scheelite structure (CaWO_{4}) in space group I4_{1}/a (Sillen & Nylander, 1943). In the title structure, the Ca^{2+} position of the original CaWO_{4} structure is statistically occupied by Na^{+} and Dy^{3+} ions in an 1:1 ratio. The crystal structure of NaDy(WO_{4})_{2} is composed of a twodirection packing of isolated WO_{4} tetrahedra interconnected by distorted [(Na/Dy)O_{8}] dodecahedra, as shown in Fig. 2.