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The crystal structure of lithium potassium tungstate monohydrate, LiKWO4·H2O, has been refined at room temperature. It is isomorphous with its molybdate analogue. The structure can be viewed as consisting of undulating sheets formed by corner sharing of WO4 and LiO4 tetrahedra, held together by hydrogen bonding.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536802002817/br6043sup1.cif
Contains datablocks CRYSTALS_cif, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536802002817/br6043Isup2.hkl
Contains datablock I

Key indicators

  • Single-crystal X-ray study
  • T = 293 K
  • Mean [sigma](W-O) = 0.005 Å
  • R factor = 0.020
  • wR factor = 0.020
  • Data-to-parameter ratio = 10.3

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

PLATON alerts of the form PLAT_7?? have been detected for an inorganic
structure. These tests are under development  for inorganics and
comments are welcomed. It is not necessary to supply a data
validation response form for these alerts at this time.


Red Alert Alert Level A:
PLAT_732 Alert A Angle Calc 105(6), Rep 104.50(10) .... 9.90 s.u-Ratio H1 -O1 -H2 1.555 1.555 1.555
Yellow Alert Alert Level C:
CELLV_02 Alert C The supplied cell volume s.u. differs from that calculated from the cell parameter s.u.'s by > 2 Calculated cell volume su = 4.21 Cell volume su given = 7.00 General Notes
ABSTY_01 Extra text has been found in the _exptl_absorpt_correction_type field, which should be only a single keyword. A literature citation should be included in the _exptl_absorpt_process_details field.
1 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
1 Alert Level C = Please check

Comment top

A number of phases of the general formula LiA1+B6+O4 (A = large monovalent cation; B = hexavalent Mo, W) have been reported (Choudhary & Choudhary, 1998, and references therein). They exhibit polymorphism in a wide temperature range, sometimes accompanied by an onset of interesting physical properties, such as ferroelectricity and pyroelectricity (Aleksandrov et al., 1981; Choudhary et al., 1997). While most of the sulfate and chromate members of this general formula can readily be grown as single crystals from aqueous solutions, in the case of tungstates and molybdates, this method yields the corresponding monohydrates. Moreover, when prepared as polycrystalline samples, these materials are very hygroscopic and gradually convert into the hydrated forms (Okada & Ossaka, 1981). The crystal structure of LiKWO4·H2O can be viewed as a layered structure formed by tetrahedral building blocks and held together by hydrogen bonding. It is isomorphic with its molybdate analogue (Makitova et al., 1989). W atoms bond to four O atoms, with the average W—O distance of 1.771 (4) Å. They form fairly regular WO4 tetrahedra, with the W—O—W angles ranging between 107.9 and 111.0°. The bond-valence sum (Brown & Altermatt, 1985) for W in this environment is 6.00. Li atoms are found in a tetrahedral coordination geometry as well, with one of the apical O atoms being that of the water molecule. The average Li—O bond length is 1.94 (1) Å and the O—Li—O angles range between 102.6 and 116.2°. The bond-valence sum for Li in this environment is 1.10. WO4 and LiO4 tetrahedral groups alternately share corners to form an undulating two-dimensional network (Fig. 1). The mid-plane of the puckered sheets is parallel to the crystallographic ab plane (Fig. 2). K atoms are located at the interstices in the middle of the six-membered rings formed by the WO4 and LiO4 tetrahedra. The coordination environment of each K atom includes a total of eight O atoms, six of them belonging to the WO4 groups and the remaining two to water molecules. The average K—O bond length is 2.943 Å, resulting in a bond-valence sum of 0.94 for this cation. Hydrogen bonding provides the connectivity along the crystallographic c axis between the sheets, as depicted in Fig. 2. The two unique O···H contacts are 1.78 (1) and 1.84 (1) Å, resulting in the separation at the points of closest contact between the puckered sheets of about 2.75 Å. Differential scanning calorimetry measurements show that above 373 K LiKWO4·H2O undergoes dehydration followed by a constructive phase transition into the beryllonite-type monoclinic LiKWO4.

Experimental top

The title compound was prepared by slow evaporation from an aqueous solution of stoichiometric quantities of Li2WO4 and K2WO4. White crystals up to a few mm in size were formed.

Refinement top

H atoms were found in a difference Fourier map and refined with constraints. O—H bond lengths in the water molecules were constrained to 0.92 (1) Å and the H—O—H angle to 104.5 (1) Å. A single atomic displacement parameter was used for both H atoms.

Computing details top

Data collection: SMART (Bruker, 1999); cell refinement: SMART; data reduction: SAINT (Bruker, 1999); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Watkin et al., 2001); molecular graphics: ATOMS (Shape Software, 2000).

Figures top
[Figure 1] Fig. 1. Polyhedral view of LiKWO4·H2O along the [001] direction. WO4 (pink) and and LiO4 (blue) tetrahedra share corners forming six-membered puckered rings. K atoms (purple) are located in the interstices. O atoms are shown in red and hydrogen in gray.
[Figure 2] Fig. 2. Polyhedral view of LiKWO4·H2O along the [010] direction. Six-membered rings of tetrahedra form undulating sheets held together by hydrogen bonding (black lines).
Lithium potassium tungstate monohydrate top
Crystal data top
LiKWO4·H2OF(000) = 1095.457
Mr = 311.90Dx = 3.883 Mg m3
Orthorhombic, PbcaMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2abCell parameters from 911 reflections
a = 10.671 (2) Åθ = 5.3–26.7°
b = 7.767 (2) ŵ = 22.35 mm1
c = 12.876 (3) ÅT = 293 K
V = 1067.1 (7) Å3Prism, white
Z = 80.22 × 0.08 × 0.06 mm
Data collection top
SMART 1K CCD area-detector
diffractometer
1219 independent reflections
Graphite monochromator836 reflections with I > 2σ(I)
Detector resolution: 8 pixels mm-1Rint = 0.07
ω scansθmax = 27.5°, θmin = 3.2°
Absorption correction: integration (coppens et al., 1965)
?
h = 1313
Tmin = 0.045, Tmax = 0.301k = 1010
11020 measured reflectionsl = 1616
Refinement top
Refinement on FHydrogen site location: difference Fourier map
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.020 Chebychev polynomial with 3 parameters (Carruthers & Watkin, 1979), 0.268, 0.125 and 0.184
wR(F2) = 0.020(Δ/σ)max = 0.007
S = 1.01Δρmax = 0.87 e Å3
836 reflectionsΔρmin = 0.91 e Å3
81 parametersExtinction correction: Larson (1970)
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 12.3 (10)
Crystal data top
LiKWO4·H2OV = 1067.1 (7) Å3
Mr = 311.90Z = 8
Orthorhombic, PbcaMo Kα radiation
a = 10.671 (2) ŵ = 22.35 mm1
b = 7.767 (2) ÅT = 293 K
c = 12.876 (3) Å0.22 × 0.08 × 0.06 mm
Data collection top
SMART 1K CCD area-detector
diffractometer
1219 independent reflections
Absorption correction: integration (coppens et al., 1965)
?
836 reflections with I > 2σ(I)
Tmin = 0.045, Tmax = 0.301Rint = 0.07
11020 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.02081 parameters
wR(F2) = 0.020H-atom parameters constrained
S = 1.01Δρmax = 0.87 e Å3
836 reflectionsΔρmin = 0.91 e Å3
Special details top

Experimental. The data collection nominally covered a sphere of reciprocal space, by a combination of 4 sets of exposures; each set had a different ϕ and/or 2θ angles and each exposure (30 s) covered 0.3° in ω. Crystal decay was monitored by repeating 50 initial frames at the end of data collection. Crystal to detector distance 4.51 cm.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
W10.131040 (16)0.56205 (3)0.124849 (19)0.0159
O20.2668 (4)0.5782 (7)0.2027 (4)0.0304
O30.1694 (5)0.4688 (5)0.0056 (4)0.0270
O40.0668 (4)0.7708 (5)0.1022 (3)0.0231
O50.0193 (4)0.4337 (6)0.1933 (3)0.0269
O10.9492 (4)0.1350 (6)0.1037 (3)0.0267
K10.19690 (11)0.30668 (19)0.36823 (11)0.0274
LI10.4315 (9)0.4838 (13)0.1775 (7)0.0181
H10.947 (8)0.164 (9)0.0345 (16)0.043 (18)*
H20.974 (8)0.234 (5)0.137 (5)0.043 (18)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
W10.01885 (13)0.01599 (13)0.01286 (13)0.00162 (9)0.0011 (1)0.00208 (9)
O20.023 (2)0.041 (3)0.027 (2)0.006 (2)0.0038 (18)0.004 (2)
O30.034 (2)0.021 (2)0.026 (2)0.0042 (19)0.002 (2)0.0066 (19)
O40.030 (2)0.019 (2)0.020 (3)0.0027 (17)0.0045 (18)0.0021 (15)
O50.032 (2)0.027 (2)0.022 (2)0.008 (2)0.0071 (18)0.0051 (19)
O10.035 (2)0.0195 (19)0.025 (2)0.0032 (19)0.0065 (19)0.0019 (17)
K10.0301 (5)0.0276 (6)0.0244 (6)0.0026 (5)0.0012 (6)0.0004 (7)
Li10.020 (5)0.020 (5)0.014 (5)0.002 (4)0.005 (4)0.002 (4)
Geometric parameters (Å, º) top
O1—H10.92 (3)Li1—O1iii1.98 (1)
O1—H20.92 (5)K1—O2i2.801 (5)
W1—O21.766 (4)K1—O23.090 (6)
W1—O31.746 (4)K1—O3iv2.792 (5)
W1—O41.784 (4)K1—O3v2.865 (5)
W1—O51.786 (4)K1—O4vi2.853 (5)
Li1—O21.93 (1)K1—O53.104 (5)
Li1—O4i1.92 (1)K1—O1vii3.011 (5)
Li1—O5ii1.95 (1)K1—O1viii3.026 (5)
H1—O1—H2104.5 (1)O4i—Li1—O2114.9 (2)
O3—W1—O2109.6 (2)O4i—Li1—O5ii104.7 (2)
O3—W1—O4108.9 (2)O2—Li1—O5ii111.7 (2)
O2—W1—O4110.1 (2)O4i—Li1—O1iii105.3 (2)
O3—W1—O5111.0 (2)O2—Li1—O1iii116.2 (2)
O2—W1—O5107.9 (2)O5ii—Li1—O1iii102.6 (2)
O4—W1—O5109.3 (2)
Symmetry codes: (i) x+1/2, y1/2, z; (ii) x+1/2, y, z+1/2; (iii) x+3/2, y+1/2, z; (iv) x, y+1/2, z+1/2; (v) x+1/2, y+1, z+1/2; (vi) x, y1/2, z+1/2; (vii) x+1, y+1/2, z+1/2; (viii) x1/2, y, z+1/2.

Experimental details

Crystal data
Chemical formulaLiKWO4·H2O
Mr311.90
Crystal system, space groupOrthorhombic, Pbca
Temperature (K)293
a, b, c (Å)10.671 (2), 7.767 (2), 12.876 (3)
V3)1067.1 (7)
Z8
Radiation typeMo Kα
µ (mm1)22.35
Crystal size (mm)0.22 × 0.08 × 0.06
Data collection
DiffractometerSMART 1K CCD area-detector
diffractometer
Absorption correctionIntegration (Coppens et al., 1965)
Tmin, Tmax0.045, 0.301
No. of measured, independent and
observed [I > 2σ(I)] reflections
11020, 1219, 836
Rint0.07
(sin θ/λ)max1)0.649
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.020, 0.020, 1.01
No. of reflections836
No. of parameters81
No. of restraints?
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.87, 0.91

Computer programs: SMART (Bruker, 1999), SMART, SAINT (Bruker, 1999), SIR92 (Altomare et al., 1994), CRYSTALS (Watkin et al., 2001), ATOMS (Shape Software, 2000).

Selected geometric parameters (Å, º) top
W1—O21.766 (4)K1—O2i2.801 (5)
W1—O31.746 (4)K1—O23.090 (6)
W1—O41.784 (4)K1—O3iv2.792 (5)
W1—O51.786 (4)K1—O3v2.865 (5)
Li1—O21.93 (1)K1—O4vi2.853 (5)
Li1—O4i1.92 (1)K1—O53.104 (5)
Li1—O5ii1.95 (1)K1—O1vii3.011 (5)
Li1—O1iii1.98 (1)K1—O1viii3.026 (5)
O3—W1—O2109.6 (2)O4i—Li1—O2114.9 (2)
O3—W1—O4108.9 (2)O4i—Li1—O5ii104.7 (2)
O2—W1—O4110.1 (2)O2—Li1—O5ii111.7 (2)
O3—W1—O5111.0 (2)O4i—Li1—O1iii105.3 (2)
O2—W1—O5107.9 (2)O2—Li1—O1iii116.2 (2)
O4—W1—O5109.3 (2)O5ii—Li1—O1iii102.6 (2)
Symmetry codes: (i) x+1/2, y1/2, z; (ii) x+1/2, y, z+1/2; (iii) x+3/2, y+1/2, z; (iv) x, y+1/2, z+1/2; (v) x+1/2, y+1, z+1/2; (vi) x, y1/2, z+1/2; (vii) x+1, y+1/2, z+1/2; (viii) x1/2, y, z+1/2.
 

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