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
Key indicators
- Single-crystal X-ray study
- T = 293 K
- Mean (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.
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
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
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field, which should be only a single keyword. A literature
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1 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
1 Alert Level C = Please check
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.
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.
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).
Lithium potassium tungstate monohydrate
top
Crystal data top
LiKWO4·H2O | F(000) = 1095.457 |
Mr = 311.90 | Dx = 3.883 Mg m−3 |
Orthorhombic, Pbca | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ac 2ab | Cell parameters from 911 reflections |
a = 10.671 (2) Å | θ = 5.3–26.7° |
b = 7.767 (2) Å | µ = 22.35 mm−1 |
c = 12.876 (3) Å | T = 293 K |
V = 1067.1 (7) Å3 | Prism, white |
Z = 8 | 0.22 × 0.08 × 0.06 mm |
Data collection top
SMART 1K CCD area-detector diffractometer | 1219 independent reflections |
Graphite monochromator | 836 reflections with I > 2σ(I) |
Detector resolution: 8 pixels mm-1 | Rint = 0.07 |
ω scans | θmax = 27.5°, θmin = 3.2° |
Absorption correction: integration (coppens et al., 1965) ? | h = −13→13 |
Tmin = 0.045, Tmax = 0.301 | k = −10→10 |
11020 measured reflections | l = −16→16 |
Refinement top
Refinement on F | Hydrogen site location: difference Fourier map |
Least-squares matrix: full | H-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 = 1.01 | Δρmax = 0.87 e Å−3 |
836 reflections | Δρmin = −0.91 e Å−3 |
81 parameters | Extinction correction: Larson (1970) |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 12.3 (10) |
Crystal data top
LiKWO4·H2O | V = 1067.1 (7) Å3 |
Mr = 311.90 | Z = 8 |
Orthorhombic, Pbca | Mo Kα radiation |
a = 10.671 (2) Å | µ = 22.35 mm−1 |
b = 7.767 (2) Å | T = 293 K |
c = 12.876 (3) Å | 0.22 × 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 = 0.301 | Rint = 0.07 |
11020 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.020 | 81 parameters |
wR(F2) = 0.020 | H-atom parameters constrained |
S = 1.01 | Δρmax = 0.87 e Å−3 |
836 reflections | Δρmin = −0.91 e Å−3 |
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 | x | y | z | Uiso*/Ueq | |
W1 | 0.131040 (16) | 0.56205 (3) | 0.124849 (19) | 0.0159 | |
O2 | 0.2668 (4) | 0.5782 (7) | 0.2027 (4) | 0.0304 | |
O3 | 0.1694 (5) | 0.4688 (5) | 0.0056 (4) | 0.0270 | |
O4 | 0.0668 (4) | 0.7708 (5) | 0.1022 (3) | 0.0231 | |
O5 | 0.0193 (4) | 0.4337 (6) | 0.1933 (3) | 0.0269 | |
O1 | 0.9492 (4) | 0.1350 (6) | 0.1037 (3) | 0.0267 | |
K1 | 0.19690 (11) | 0.30668 (19) | 0.36823 (11) | 0.0274 | |
LI1 | 0.4315 (9) | 0.4838 (13) | 0.1775 (7) | 0.0181 | |
H1 | 0.947 (8) | 0.164 (9) | 0.0345 (16) | 0.043 (18)* | |
H2 | 0.974 (8) | 0.234 (5) | 0.137 (5) | 0.043 (18)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
W1 | 0.01885 (13) | 0.01599 (13) | 0.01286 (13) | 0.00162 (9) | 0.0011 (1) | −0.00208 (9) |
O2 | 0.023 (2) | 0.041 (3) | 0.027 (2) | 0.006 (2) | −0.0038 (18) | −0.004 (2) |
O3 | 0.034 (2) | 0.021 (2) | 0.026 (2) | 0.0042 (19) | 0.002 (2) | −0.0066 (19) |
O4 | 0.030 (2) | 0.019 (2) | 0.020 (3) | −0.0027 (17) | −0.0045 (18) | 0.0021 (15) |
O5 | 0.032 (2) | 0.027 (2) | 0.022 (2) | −0.008 (2) | 0.0071 (18) | −0.0051 (19) |
O1 | 0.035 (2) | 0.0195 (19) | 0.025 (2) | 0.0032 (19) | −0.0065 (19) | −0.0019 (17) |
K1 | 0.0301 (5) | 0.0276 (6) | 0.0244 (6) | 0.0026 (5) | −0.0012 (6) | 0.0004 (7) |
Li1 | 0.020 (5) | 0.020 (5) | 0.014 (5) | 0.002 (4) | 0.005 (4) | 0.002 (4) |
Geometric parameters (Å, º) top
O1—H1 | 0.92 (3) | Li1—O1iii | 1.98 (1) |
O1—H2 | 0.92 (5) | K1—O2i | 2.801 (5) |
W1—O2 | 1.766 (4) | K1—O2 | 3.090 (6) |
W1—O3 | 1.746 (4) | K1—O3iv | 2.792 (5) |
W1—O4 | 1.784 (4) | K1—O3v | 2.865 (5) |
W1—O5 | 1.786 (4) | K1—O4vi | 2.853 (5) |
Li1—O2 | 1.93 (1) | K1—O5 | 3.104 (5) |
Li1—O4i | 1.92 (1) | K1—O1vii | 3.011 (5) |
Li1—O5ii | 1.95 (1) | K1—O1viii | 3.026 (5) |
| | | |
H1—O1—H2 | 104.5 (1) | O4i—Li1—O2 | 114.9 (2) |
O3—W1—O2 | 109.6 (2) | O4i—Li1—O5ii | 104.7 (2) |
O3—W1—O4 | 108.9 (2) | O2—Li1—O5ii | 111.7 (2) |
O2—W1—O4 | 110.1 (2) | O4i—Li1—O1iii | 105.3 (2) |
O3—W1—O5 | 111.0 (2) | O2—Li1—O1iii | 116.2 (2) |
O2—W1—O5 | 107.9 (2) | O5ii—Li1—O1iii | 102.6 (2) |
O4—W1—O5 | 109.3 (2) | | |
Symmetry codes: (i) −x+1/2, y−1/2, 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, y−1/2, −z+1/2; (vii) −x+1, y+1/2, −z+1/2; (viii) x−1/2, y, −z+1/2. |
Experimental details
Crystal data |
Chemical formula | LiKWO4·H2O |
Mr | 311.90 |
Crystal system, space group | Orthorhombic, Pbca |
Temperature (K) | 293 |
a, b, c (Å) | 10.671 (2), 7.767 (2), 12.876 (3) |
V (Å3) | 1067.1 (7) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 22.35 |
Crystal size (mm) | 0.22 × 0.08 × 0.06 |
|
Data collection |
Diffractometer | SMART 1K CCD area-detector diffractometer |
Absorption correction | Integration (Coppens et al., 1965) |
Tmin, Tmax | 0.045, 0.301 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 11020, 1219, 836 |
Rint | 0.07 |
(sin θ/λ)max (Å−1) | 0.649 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.020, 0.020, 1.01 |
No. of reflections | 836 |
No. of parameters | 81 |
No. of restraints | ? |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.87, −0.91 |
Selected geometric parameters (Å, º) topW1—O2 | 1.766 (4) | K1—O2i | 2.801 (5) |
W1—O3 | 1.746 (4) | K1—O2 | 3.090 (6) |
W1—O4 | 1.784 (4) | K1—O3iv | 2.792 (5) |
W1—O5 | 1.786 (4) | K1—O3v | 2.865 (5) |
Li1—O2 | 1.93 (1) | K1—O4vi | 2.853 (5) |
Li1—O4i | 1.92 (1) | K1—O5 | 3.104 (5) |
Li1—O5ii | 1.95 (1) | K1—O1vii | 3.011 (5) |
Li1—O1iii | 1.98 (1) | K1—O1viii | 3.026 (5) |
| | | |
O3—W1—O2 | 109.6 (2) | O4i—Li1—O2 | 114.9 (2) |
O3—W1—O4 | 108.9 (2) | O4i—Li1—O5ii | 104.7 (2) |
O2—W1—O4 | 110.1 (2) | O2—Li1—O5ii | 111.7 (2) |
O3—W1—O5 | 111.0 (2) | O4i—Li1—O1iii | 105.3 (2) |
O2—W1—O5 | 107.9 (2) | O2—Li1—O1iii | 116.2 (2) |
O4—W1—O5 | 109.3 (2) | O5ii—Li1—O1iii | 102.6 (2) |
Symmetry codes: (i) −x+1/2, y−1/2, 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, y−1/2, −z+1/2; (vii) −x+1, y+1/2, −z+1/2; (viii) x−1/2, y, −z+1/2. |
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.