Scheelite-type NaDy(WO₄)₂

The title compound sodium dysprosium(III) bis­[tungs­tate(VI)], NaDy(WO₄)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 WO₄ tetra­hedra ( symmetry) with one set of bond lengths and distorted [(Na/Dy)O₈] dodeca­hedra ( symmetry; occupancy ratio Na:Dy = 1:1) with two sets of bond lengths.

Related literature

For the structures, properties and applications of alkali rare-earth bis-tungstates with general formula ARE(WO₄)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 (CaWO₄) structure, see: Sillen & Nylander (1943).

Experimental

Crystal data

• NaDy(WO₄)₂

• M_r = 681.19

• Tetragonal, I 4₁ /a

• a = 5.2545 (5) Å

• c = 11.4029 (15) Å

• V = 314.83 (6) ų

• Z = 2

• Mo Kα radiation

• μ = 48.27 mm⁻¹

• T = 298 K

• 0.10 × 0.10 × 0.08 mm

Data collection

• Rigaku Mercury70 diffractometer

• Absorption correction: multi-scan (SADABS; Sheldrick, 1997) T_min = 0.263, T_max = 1.000

• 1128 measured reflections

• 181 independent reflections

• 143 reflections with I > 2σ(I)

• R_int = 0.053

Refinement

• R[F² > 2σ(F²)] = 0.024

• wR(F²) = 0.056

• S = 0.87

• 181 reflections

• 15 parameters

• Δρ_max = 1.55 e Å⁻³

• Δρ_min = −1.40 e Å⁻³

Table 1
Selected bond lengths (Å)

(Na/Dy)1—O1^i	2.457 (7)
(Na/Dy)1—O1	2.471 (7)
W1—O1	1.785 (7)
Symmetry code: (i) .

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).

Supporting information

S1. Comment

In the past years an increasing interest in the synthesis and characterization of rare-earth double tungstate(VI) crystals with general formula ARE(WO₄)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 (CaWO₄) in space group I4₁/a (Sillen & Nylander, 1943). In the title structure, the Ca²⁺ position of the original CaWO₄ structure is statistically occupied by Na⁺ and Dy³⁺ ions in an 1:1 ratio. The crystal structure of NaDy(WO₄)₂ is composed of a two-direction packing of isolated WO₄ tetrahedra interconnected by distorted [(Na/Dy)O₈] dodecahedra, as shown in Fig. 2.

Related literature

For the structures, properties and applications of alkali rare-earth bis-tungstates with general formula ARE(WO₄)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 (CaWO₄) structure, see: Sillen & Nylander (1943).

S2. Experimental

Single crystal of NaDy(WO₄)₂ were prepared by a high temperature solution reaction, using analytical reagents of Dy₂O₃, Na₂CO₃ and WO₃ 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.

S3. Refinement

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/ų from the W1 site, and the deepest hole is -1.40 e/ų from the Na1/Dy1 site.

Computing details

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

Figures

	Fig. 1. Part of the structure of NaDy(WO4)2 showing the labelling of the atoms (displacement ellipsoids are drawn at the 50% probability level).
	Fig. 2. View of the crystal structure of NaDy(WO4)2 (WO4 tetrahedra are shaded in sea-green; Na/Dy atoms are drawn as yellow balls).

Sodium dysprosium(III) bis[tungstate(VI)]

Crystal data

NaDy(WO4)2	Dx = 7.186 Mg m^−3
Mr = 681.19	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, I41/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

Data collection

Rigaku Mercury70 diffractometer	181 independent reflections
Radiation source: fine-focus sealed tube	143 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.053
Detector resolution: 14.6306 pixels mm^-1	θmax = 27.5°, θmin = 4.3°
ω scans	h = −6→6
Absorption correction: multi-scan (SADABS; Bruker, 1997)	k = −6→6
Tmin = 0.263, Tmax = 1.000	l = −14→13
1128 measured reflections

Refinement

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(Fo^2) + (0.0045P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.056	(Δ/σ)max < 0.001
S = 0.87	Δρmax = 1.55 e Å^−3
181 reflections	Δρmin = −1.40 e Å^−3
15 parameters	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0295 (17)

Special details

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	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)

Atomic displacement parameters (Ų)

	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)

Geometric parameters (Å, º)

(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.