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Acta Crystallogr Sect E Struct Rep Online. 2010 January 1; 66(Pt 1): i2.

Published online 2009 December 12. doi: 10.1107/S1600536809052271

PMCID: PMC2980022

Correspondence e-mail: nc.ude.uph@dzmai

Received 2009 December 1; Accepted 2009 December 4.

Copyright © Zhao et al. 2010

This is an open-access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

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.

For the structures, properties and applications of alkali rare-earth bis-tungstates with general formula *ARE*(WO_{4})_{2} (*A* = alkali metal, *RE* = rare-earth 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 ).

- NaDy(WO
_{4})_{2} *M*= 681.19_{r}- Tetragonal,
*a*= 5.2545 (5) Å*c*= 11.4029 (15) Å*V*= 314.83 (6) Å^{3}*Z*= 2- Mo
*K*α radiation - μ = 48.27 mm
^{−1} *T*= 298 K- 0.10 × 0.10 × 0.08 mm

*R*[*F*^{2}> 2σ(*F*^{2})] = 0.024*wR*(*F*^{2}) = 0.056*S*= 0.87- 181 reflections
- 15 parameters
- Δρ
_{max}= 1.55 e Å^{−3} - Δρ
_{min}= −1.40 e Å^{−3}

Data collection: *CrystalClear* (Rigaku, 2000 ); cell refinement: *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 ).

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809052271/wm2287sup1.cif

Click here to view.^{(13K, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809052271/wm2287Isup2.hkl

Click here to view.^{(9.8K, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

In the past years an increasing interest in the synthesis and characterization
of rare-earth double tungstate(VI) crystals with general formula
*ARE*(WO_{4})_{2} (*A* = alkali metal, *RE* = rare-earth
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
solid-state laser host materials because of their large rare-earth ion
admittance.
Most of these crystals have tetragonal symmetry and crystallize with the
scheelite structure (CaWO_{4}) in space group *I*4_{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 two-direction packing
of isolated WO_{4} tetrahedra interconnected by distorted [(Na/Dy)O_{8}]
dodecahedra, as shown in Fig. 2.

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 homogeneity 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 substitutional-type 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 least-squares
refinement, 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 electron density map
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.

Part of the structure of NaDy(WO4)2 showing the labelling of the atoms (displacement ellipsoids are drawn at the 50% probability level).

NaDy(WO_{4})_{2} | D_{x} = 7.186 Mg m^{−}^{3} |

M = 681.19_{r} | 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: fine-focus sealed tube | 143 reflections with I > 2σ(I) |

graphite | 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: multi-scan (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: structure-invariant direct methods |

Least-squares 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) |

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. |

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.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: WM2287).

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