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Single crystals of the title compound, lithium potassium dichromium(III) arsenate(V), have been prepared by a solid-state reaction. The compound adopts the garnet structure. The monovalent cations share the same site (Wyckoff position 24c), with 81 (2) and 19 (2)% occupancy for Li and K, respectively, resulting in an eightfold coordination by O atoms.
Supporting information
Key indicators
- Single-crystal X-ray study
- T = 293 K
- Mean (r-O) = 0.003 Å
- Disorder in main residue
- R factor = 0.028
- wR factor = 0.053
- Data-to-parameter ratio = 7.9
checkCIF/PLATON results
No syntax errors found
Alert level B
PLAT088_ALERT_3_B Poor Data / Parameter Ratio .................... 7.95
Alert level C
RINTA01_ALERT_3_C The value of Rint is greater than 0.10
Rint given 0.147
PLAT020_ALERT_3_C The value of Rint is greater than 0.10 ......... 0.15
PLAT041_ALERT_1_C Calc. and Rep. SumFormula Strings Differ .... ?
PLAT045_ALERT_1_C Calculated and Reported Z Differ by ............ 0.12 Ratio
PLAT066_ALERT_1_C Predicted and Reported Transmissions Identical . ?
PLAT068_ALERT_1_C Reported F000 Differs from Calcd (or Missing)... ?
PLAT077_ALERT_4_C Unitcell contains non-integer number of atoms .. ?
PLAT199_ALERT_1_C Check the Reported _cell_measurement_temperature 293 K
PLAT200_ALERT_1_C Check the Reported _diffrn_ambient_temperature . 293 K
PLAT301_ALERT_3_C Main Residue Disorder ......................... 7.00 Perc.
PLAT430_ALERT_2_C Short Inter D...A Contact O .. O .. 2.86 Ang.
PLAT430_ALERT_2_C Short Inter D...A Contact O .. O .. 2.88 Ang.
PLAT711_ALERT_1_C BOND Unknown or Inconsistent Label .......... K,LI
(K,LI) O
PLAT711_ALERT_1_C BOND Unknown or Inconsistent Label .......... K,LI
(K,LI) O
PLAT711_ALERT_1_C BOND Unknown or Inconsistent Label .......... K,LI
(K,LI) O
PLAT711_ALERT_1_C BOND Unknown or Inconsistent Label .......... K,LI
(K,LI) O
PLAT711_ALERT_1_C BOND Unknown or Inconsistent Label .......... K,LI
(K,LI) O
PLAT711_ALERT_1_C BOND Unknown or Inconsistent Label .......... K,LI
(K,LI) O
PLAT711_ALERT_1_C BOND Unknown or Inconsistent Label .......... K,LI
(K,LI) O
PLAT711_ALERT_1_C BOND Unknown or Inconsistent Label .......... K,LI
(K,LI) O
PLAT711_ALERT_1_C BOND Unknown or Inconsistent Label .......... K,LI
(K,LI) AS
PLAT711_ALERT_1_C BOND Unknown or Inconsistent Label .......... K,LI
(K,LI) CR
PLAT711_ALERT_1_C BOND Unknown or Inconsistent Label .......... K,LI
O (K,LI)
PLAT712_ALERT_1_C ANGLE Unknown or Inconsistent Label .......... K,LI
AS O (K,LI)
PLAT712_ALERT_1_C ANGLE Unknown or Inconsistent Label .......... K,LI
CR O (K,LI)
Alert level G
CELLZ01_ALERT_1_G Difference between formula and atom_site contents detected.
CELLZ01_ALERT_1_G ALERT: check formula stoichiometry or atom site occupancies.
From the CIF: _cell_formula_units_Z 8
From the CIF: _chemical_formula_sum As3 Cr2 K0.56 Li2.44 O12
TEST: Compare cell contents of formula and atom_site data
atom Z*formula cif sites diff
As 24.00 24.00 0.00
Cr 16.00 16.00 0.00
K 4.48 4.51 -0.03
Li 19.52 19.49 0.03
O 96.00 96.00 0.00
0 ALERT level A = In general: serious problem
1 ALERT level B = Potentially serious problem
25 ALERT level C = Check and explain
2 ALERT level G = General alerts; check
21 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
2 ALERT type 2 Indicator that the structure model may be wrong or deficient
4 ALERT type 3 Indicator that the structure quality may be low
1 ALERT type 4 Improvement, methodology, query or suggestion
Data collection: CAD-4 EXPRESS (Duisenberg, 1992; Macíček & Yordanov, 1992); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 1998); software used to prepare material for publication: SHELXL97.
Lithium potassium dichromium(III) arsenate(V)
top
Crystal data top
Li2.44K0.56Cr2(AsO4)3 | Dx = 4.359 Mg m−3 |
Mr = 559.67 | Mo Kα radiation, λ = 0.71069 Å |
Cubic, Ia3d | Cell parameters from 25 reflections |
Hall symbol: -I 4bd 2c 3 | θ = 12–16° |
a = 11.948 (1) Å | µ = 14.45 mm−1 |
V = 1705.6 (2) Å3 | T = 293 K |
Z = 8 | Fragment, green |
F(000) = 2088 | 0.21 × 0.18 × 0.11 mm |
Data collection top
Enraf–Nonius CAD-4 diffractometer | 145 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.147 |
Graphite monochromator | θmax = 26.9°, θmin = 4.2° |
ω/2θ scans | h = −15→0 |
Absorption correction: ψ scan (North et al., 1968) | k = 0→15 |
Tmin = 0.062, Tmax = 0.204 | l = 0→15 |
842 measured reflections | 2 standard reflections every 120 min |
159 independent reflections | intensity decay: 1.2% |
Refinement top
Refinement on F2 | Primary atom site location: heavy-atom method |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.028 | w = 1/[σ2(Fo2)] |
wR(F2) = 0.053 | (Δ/σ)max = 0.006 |
S = 1.15 | Δρmax = 0.62 e Å−3 |
159 reflections | Δρmin = −0.59 e Å−3 |
20 parameters | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
1 restraint | Extinction coefficient: 0.0018 (3) |
Special details top
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 (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
Cr | 0.0000 | 0.0000 | 0.0000 | 0.0046 (4) | |
As | 0.2500 | −0.1250 | 0.0000 | 0.0048 (4) | |
K | 0.2500 | 0.1250 | 0.0000 | 0.040 (3) | 0.188 (16) |
Li | 0.2500 | 0.1250 | 0.0000 | 0.040 (3) | 0.812 (17) |
O | 0.1528 (2) | −0.0356 (2) | 0.0495 (2) | 0.0090 (6) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Cr | 0.0046 (4) | 0.0046 (4) | 0.0046 (4) | −0.0001 (3) | −0.0001 (3) | −0.0001 (3) |
As | 0.0046 (4) | 0.0052 (5) | 0.0046 (4) | 0.000 | 0.000 | 0.000 |
K | 0.049 (4) | 0.021 (5) | 0.049 (4) | 0.000 | 0.002 (3) | 0.000 |
Li | 0.049 (4) | 0.021 (5) | 0.049 (4) | 0.000 | 0.002 (3) | 0.000 |
O | 0.0062 (13) | 0.0117 (14) | 0.0092 (13) | 0.0012 (10) | −0.0003 (9) | −0.0020 (9) |
Geometric parameters (Å, º) top
Cr—O | 1.965 (3) | (K,Li)—O | 2.320 (2) |
Cr—Oi | 1.965 (3) | (K,Li)—Ox | 2.320 (2) |
Cr—Oii | 1.965 (3) | (K,Li)—Ovii | 2.320 (2) |
Cr—Oiii | 1.965 (3) | (K,Li)—Oxi | 2.456 (2) |
Cr—Oiv | 1.965 (3) | (K,Li)—Oxii | 2.456 (2) |
Cr—Ov | 1.965 (3) | (K,Li)—Oxiii | 2.456 (2) |
As—Ovi | 1.685 (3) | (K,Li)—Oii | 2.456 (2) |
As—Ovii | 1.685 (3) | (K,Li)—Asxiv | 2.9870 (2) |
As—Oviii | 1.685 (3) | (K,Li)—Crxv | 3.3396 (3) |
As—O | 1.685 (3) | O—Liiv | 2.456 (2) |
(K,Li)—Oix | 2.320 (2) | O—(K,Li)iv | 2.456 (2) |
| | | |
Ovi—As—Ovii | 113.67 (8) | Oviii—As—O | 113.67 (8) |
Ovi—As—Oviii | 101.37 (16) | As—O—Crxvi | 64.62 (7) |
Ovii—As—Oviii | 113.67 (8) | As—O—(K,Li) | 95.13 (10) |
Ovi—As—O | 113.67 (8) | Crxvi—O—(K,Li) | 102.07 (11) |
Ovii—As—O | 101.37 (16) | | |
Symmetry codes: (i) −z, −x, −y; (ii) z, x, y; (iii) −y, −z, −x; (iv) y, z, x; (v) −x, −y, −z; (vi) −z+1/4, −y−1/4, x−1/4; (vii) −x+1/2, y, −z; (viii) z+1/4, −y−1/4, −x+1/4; (ix) −z+1/4, −y+1/4, −x+1/4; (x) z+1/4, −y+1/4, x−1/4; (xi) y+1/4, −x+1/4, z−1/4; (xii) −z+1/2, x, −y; (xiii) −y+1/4, −x+1/4, −z+1/4; (xiv) x, y+1/2, −z; (xv) y+1/4, x+1/4, z+1/4; (xvi) x+1/4, −z−1/4, −y+1/4. |
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