Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270108002801/sq3118sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270108002801/sq3118Isup2.hkl |
For related literature, see: Capsoni et al. (2006); Kampf et al. (1973); Kipka & Müller-Buschbaum (1976); Knorr et al. (1999); Müller-Buschbaum & Rettich (1997); Malcherek et al. (2001); Reeswinkel et al. (2007).
Ba3Li2V2O7Cl4 was prepared via a molten salt reaction as a by-product during the synthesis of the V4+ compound BaV4O9 (Reeswinkel et al., 2007). A mixture of LiCl, RbCl and BaCl2 was first prepared by drying the components separately at 413 K and mixing them in the molar ratio 2:1:1. VO2 powder was added to the mixture in a flux to a VO2 molar ratio of 10:1. The sample was ground, placed in an Al2O3 crucible and briefly dried to remove water from the hygroscopic BaCl2. The crucible was then placed in a glass test tube within a glass gas-washing bottle. The sample was heat treated at 713 K for 24 d in a vertical tube furnace. During that time, argon gas (Ar 5.0) was flushed through the bottle. At the end of the growth process, the sample was slowly cooled down to room temperature.
Despite the fact that the unit-cell metric and the positions of the Ba, Li, Cl and O atoms suggest the orthorhombic space group Cmmm, the structure has to be described in the monoclinic crystal system. The internal R value of the data set before absorption correction is 9% for the 2/m Laue class and 24.9% for the mmm Laue class. Furthermore, the Cmmm symmetry would not allow the ordering of the V (Z = 23) and Li (Z = 3) atoms within the Li2V4O18 rings, although it is clearly visible in the monoclinic symmetry.
Structure solution using direct methods gave the positions of the Ba, V, O and Cl atoms. The Li atoms were located subsequently from a residual electron-density analysis after refinement of the structure. All atoms could be refined with anisotropic displacement parameters. A possible presence of Rb from the salt mixture on the Ba sites was tested by site-occupancy refinement and proved to be insignificant.
Data collection: X-AREA (Stoe & Cie, 2000); cell refinement: X-AREA (Stoe & Cie, 2000); data reduction: X-RED (Stoe & Cie, 1996); program(s) used to solve structure: SIR2002 (Burla et al., 2003); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ATOMS (Dowty, 2000); software used to prepare material for publication: WinGX (Version 1.70.01; Farrugia, 1999).
Ba3Li2V2O7Cl4 | F(000) = 1376 |
Mr = 781.58 | Dx = 3.886 Mg m−3 |
Monoclinic, C2/m | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -C 2y | Cell parameters from 20576 reflections |
a = 16.1215 (14) Å | θ = 2.8–35.2° |
b = 5.7630 (3) Å | µ = 10.87 mm−1 |
c = 14.3795 (13) Å | T = 293 K |
β = 90.592 (7)° | Parallelepiped, blue |
V = 1335.90 (18) Å3 | 0.19 × 0.15 × 0.12 mm |
Z = 4 |
Stoe IPDSII diffractometer | 2763 reflections with I > 2σ(I) |
Rotation method, ω scans | Rint = 0.051 |
Absorption correction: numerical (X-SHAPE; Stoe & Cie, 1996) | θmax = 35.0°, θmin = 2.8° |
Tmin = 0.141, Tmax = 0.295 | h = −26→25 |
22838 measured reflections | k = −9→7 |
3141 independent reflections | l = −22→23 |
Refinement on F2 | 0 constraints |
Least-squares matrix: full | w = 1/σ2(Fo2) |
R[F2 > 2σ(F2)] = 0.024 | (Δ/σ)max < 0.001 |
wR(F2) = 0.035 | Δρmax = 1.02 e Å−3 |
S = 1.61 | Δρmin = −1.27 e Å−3 |
3141 reflections | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
106 parameters | Extinction coefficient: 0.00627 (10) |
0 restraints |
Ba3Li2V2O7Cl4 | V = 1335.90 (18) Å3 |
Mr = 781.58 | Z = 4 |
Monoclinic, C2/m | Mo Kα radiation |
a = 16.1215 (14) Å | µ = 10.87 mm−1 |
b = 5.7630 (3) Å | T = 293 K |
c = 14.3795 (13) Å | 0.19 × 0.15 × 0.12 mm |
β = 90.592 (7)° |
Stoe IPDSII diffractometer | 3141 independent reflections |
Absorption correction: numerical (X-SHAPE; Stoe & Cie, 1996) | 2763 reflections with I > 2σ(I) |
Tmin = 0.141, Tmax = 0.295 | Rint = 0.051 |
22838 measured reflections |
R[F2 > 2σ(F2)] = 0.024 | 106 parameters |
wR(F2) = 0.035 | 0 restraints |
S = 1.61 | Δρmax = 1.02 e Å−3 |
3141 reflections | Δρmin = −1.27 e Å−3 |
Experimental. The single-crystal X-ray diffraction measurement was performed on a two-circle imaging plate diffractometer (Stoe IPDSII, Mo Kα-radiation, tube setting 50 kV and 25 mA, pyrolytic graphite monochromator). The data were collected using a crystal-detector distance of 6 cm, an exposure time of 2.5 min per frame, an ω-scan between 0° and 180° for ϕ = 0° and ω-scans between 0° and 120° for ϕ = 45° and ϕ = 90°, with the rotation step Δω = 1.5° per frame. |
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. |
x | y | z | Uiso*/Ueq | ||
Ba1 | 0.133937 (10) | 0 | 0.279261 (13) | 0.01316 (4) | |
Ba2 | 0.136184 (10) | 0 | 0.726277 (13) | 0.01414 (4) | |
Ba3 | 0.5 | 0 | 0 | 0.01659 (6) | |
Ba4 | 0.5 | 0 | 0.5 | 0.01711 (6) | |
V1 | 0.31140 (3) | 0 | 0.87285 (3) | 0.00853 (8) | |
V2 | 0.49634 (3) | 0 | 0.25169 (3) | 0.00830 (8) | |
Cl1 | 0.31137 (4) | 0 | 0.37832 (5) | 0.01569 (13) | |
Cl2 | 0.00143 (6) | 0 | 0.11521 (6) | 0.02670 (18) | |
Cl3 | 0.31537 (4) | 0 | 0.62089 (5) | 0.01562 (13) | |
Cl4 | 0.11507 (5) | 0 | 0.50133 (5) | 0.01677 (13) | |
O1 | 0.32993 (14) | 0 | 0.98736 (15) | 0.0177 (5) | |
O2 | 0.41184 (13) | 0 | 0.18266 (16) | 0.0185 (5) | |
O3 | 0.49752 (9) | 0.2336 (3) | 0.32264 (11) | 0.0132 (3) | |
O4 | 0.25850 (9) | 0.2358 (3) | 0.83436 (11) | 0.0153 (3) | |
O5 | 0.41276 (13) | 0 | 0.82120 (17) | 0.0178 (5) | |
Li1 | 0.3017 (3) | 0 | 0.1166 (4) | 0.0130 (10) | |
Li2 | 0.25 | 0.25 | 0.5 | 0.0280 (14) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Ba1 | 0.01104 (7) | 0.01398 (8) | 0.01448 (9) | 0 | 0.00141 (5) | 0 |
Ba2 | 0.00985 (7) | 0.01665 (9) | 0.01588 (9) | 0 | −0.00218 (5) | 0 |
Ba3 | 0.01104 (9) | 0.02688 (14) | 0.01181 (11) | 0 | −0.00209 (7) | 0 |
Ba4 | 0.01941 (11) | 0.02040 (13) | 0.01153 (11) | 0 | 0.00064 (8) | 0 |
V1 | 0.00700 (16) | 0.01017 (19) | 0.0084 (2) | 0 | 0.00044 (13) | 0 |
V2 | 0.00686 (16) | 0.00952 (19) | 0.00852 (17) | 0 | 0.00053 (13) | 0 |
Cl1 | 0.0145 (3) | 0.0158 (3) | 0.0168 (3) | 0 | 0.0017 (2) | 0 |
Cl2 | 0.0419 (5) | 0.0238 (4) | 0.0144 (3) | 0 | −0.0009 (3) | 0 |
Cl3 | 0.0156 (3) | 0.0157 (3) | 0.0155 (3) | 0 | −0.0013 (2) | 0 |
Cl4 | 0.0174 (3) | 0.0185 (3) | 0.0144 (3) | 0 | 0.0003 (2) | 0 |
O1 | 0.0163 (9) | 0.0288 (13) | 0.0080 (9) | 0 | −0.0002 (7) | 0 |
O2 | 0.0098 (8) | 0.0297 (13) | 0.0159 (10) | 0 | −0.0028 (7) | 0 |
O3 | 0.0128 (6) | 0.0131 (7) | 0.0137 (7) | −0.0004 (5) | 0.0010 (5) | −0.0021 (6) |
O4 | 0.0138 (6) | 0.0140 (7) | 0.0181 (7) | 0.0049 (6) | 0.0002 (5) | −0.0006 (6) |
O5 | 0.0094 (8) | 0.0275 (13) | 0.0166 (10) | 0 | 0.0037 (7) | 0 |
Li1 | 0.014 (2) | 0.013 (2) | 0.012 (2) | 0 | 0.0034 (17) | 0 |
Li2 | 0.037 (4) | 0.022 (3) | 0.025 (3) | 0.003 (3) | 0.000 (2) | 0.003 (3) |
Ba1—O3i | 2.7589 (16) | V1—Cl2iv | 4.1746 (8) |
Ba1—O3ii | 2.7589 (16) | V1—Cl2v | 4.1746 (8) |
Ba1—O4iii | 2.8377 (18) | V1—V1xx | 5.0737 (8) |
Ba1—O4iv | 2.8377 (18) | V1—V1xxi | 5.0737 (8) |
Ba1—Cl2 | 3.1660 (9) | V1—Li2iii | 5.6294 (6) |
Ba1—Cl1 | 3.1824 (8) | V1—Li2 | 5.6294 (6) |
Ba1—Cl4 | 3.2108 (8) | V1—V1xxii | 5.7630 (3) |
Ba1—O5v | 3.3067 (11) | V2—O2 | 1.677 (2) |
Ba1—O5iv | 3.3067 (11) | V2—O3 | 1.6891 (16) |
Ba1—Cl3iv | 3.3179 (4) | V2—O3viii | 1.6891 (16) |
Ba1—Cl3v | 3.3179 (4) | V2—O5ix | 1.810 (2) |
Ba1—Li1 | 3.594 (5) | V2—Cl2xv | 3.4877 (6) |
Ba1—V2i | 3.6555 (3) | V2—Cl2xiii | 3.4877 (6) |
Ba1—V2vi | 3.6555 (3) | V2—Cl1 | 3.5099 (9) |
Ba1—V1v | 3.7288 (4) | V2—Cl3ix | 3.5295 (9) |
Ba1—V1iv | 3.7288 (4) | V2—V1ix | 3.5957 (7) |
Ba1—Li2 | 3.9407 (3) | V2—Ba2v | 3.6030 (3) |
Ba1—Li2iii | 3.9407 (3) | V2—Ba2iv | 3.6030 (3) |
Ba1—Ba2vii | 4.3547 (4) | V2—Ba1xiii | 3.6555 (3) |
Ba1—Ba2iv | 4.6957 (3) | V2—Ba1xv | 3.6555 (3) |
Ba2—O3iii | 2.7325 (16) | V2—Li1 | 3.673 (5) |
Ba2—O3iv | 2.7325 (15) | V2—Li2iii | 5.5579 (6) |
Ba2—O4 | 2.8439 (16) | V2—Li2 | 5.5579 (6) |
Ba2—O4viii | 2.8439 (16) | V2—Li2xviii | 5.5899 (6) |
Ba2—Cl2vii | 3.1971 (11) | V2—Li2xv | 5.5899 (6) |
Ba2—Cl4 | 3.2490 (8) | Cl1—Li2 | 2.4803 (6) |
Ba2—O2iv | 3.2616 (12) | Cl1—Li2iii | 2.4803 (6) |
Ba2—O2v | 3.2616 (12) | Cl1—Ba2v | 3.3625 (4) |
Ba2—Cl3 | 3.2759 (8) | Cl1—Ba2iv | 3.3625 (4) |
Ba2—Cl1v | 3.3625 (4) | Cl1—Li1 | 3.765 (5) |
Ba2—Cl1iv | 3.3625 (4) | Cl2—Ba2vii | 3.1971 (11) |
Ba2—V1 | 3.5069 (5) | Cl2—Ba3i | 3.3238 (5) |
Ba2—V2v | 3.6030 (3) | Cl2—Ba3vi | 3.3238 (5) |
Ba2—V2iv | 3.6030 (3) | Cl2—V2vi | 3.4877 (6) |
Ba2—Li1iv | 3.790 (3) | Cl2—V2i | 3.4877 (6) |
Ba2—Li1v | 3.790 (3) | Cl2—V1iv | 4.1746 (8) |
Ba2—Li2iii | 4.0191 (4) | Cl2—V1v | 4.1746 (8) |
Ba2—Li2 | 4.0191 (4) | Cl2—Li1i | 4.321 (4) |
Ba2—Ba1vii | 4.3547 (5) | Cl2—Li1vi | 4.321 (4) |
Ba2—Ba1iv | 4.6957 (3) | Cl3—Li2iii | 2.4840 (6) |
Ba3—O1ix | 2.746 (2) | Cl3—Li2 | 2.4840 (6) |
Ba3—O1x | 2.746 (2) | Cl3—Ba1iv | 3.3179 (4) |
Ba3—O5ix | 2.918 (2) | Cl3—Ba1v | 3.3179 (4) |
Ba3—O5x | 2.918 (2) | Cl3—V2ix | 3.5295 (9) |
Ba3—O2xi | 2.999 (2) | Cl4—Li2 | 2.6094 (6) |
Ba3—O2 | 2.999 (2) | Cl4—Li2iii | 2.6094 (6) |
Ba3—Cl2xii | 3.3238 (5) | Cl4—Ba4i | 3.4269 (4) |
Ba3—Cl2xiii | 3.3238 (5) | Cl4—Ba4vi | 3.4269 (4) |
Ba3—Cl2xiv | 3.3238 (5) | O1—Li1xix | 1.918 (6) |
Ba3—Cl2xv | 3.3238 (5) | O1—Ba3xix | 2.746 (2) |
Ba3—V1x | 3.5317 (5) | O1—Li1v | 3.870 (4) |
Ba3—V1ix | 3.5317 (5) | O1—Li1iv | 3.870 (4) |
Ba3—V2 | 3.6202 (6) | O2—Li1 | 2.005 (6) |
Ba3—V2xi | 3.6202 (6) | O2—Ba2iv | 3.2616 (12) |
Ba3—Li1xi | 3.625 (5) | O2—Ba2v | 3.2616 (12) |
Ba3—Li1 | 3.625 (5) | O3—Ba2iv | 2.7325 (15) |
Ba3—Ba2xvi | 5.3660 (4) | O3—Ba1xiii | 2.7589 (16) |
Ba3—Ba2iv | 5.3660 (4) | O4—Li1iv | 1.942 (4) |
Ba3—Ba2xvii | 5.3660 (4) | O4—Ba1iv | 2.8377 (18) |
Ba3—Ba2v | 5.3660 (4) | O5—V2ix | 1.810 (2) |
Ba4—O3viii | 2.8838 (16) | O5—Ba3xix | 2.918 (2) |
Ba4—O3xviii | 2.8838 (16) | O5—Ba1v | 3.3067 (11) |
Ba4—O3ix | 2.8838 (16) | O5—Ba1iv | 3.3067 (11) |
Ba4—O3 | 2.8838 (16) | Li1—O1x | 1.918 (6) |
Ba4—Cl4v | 3.4269 (4) | Li1—O4iii | 1.942 (4) |
Ba4—Cl4xiii | 3.4269 (4) | Li1—O4iv | 1.942 (4) |
Ba4—Cl4iv | 3.4269 (4) | Li1—O2 | 2.005 (6) |
Ba4—Cl4xv | 3.4269 (4) | Li1—V1v | 3.414 (3) |
Ba4—Cl3 | 3.4624 (8) | Li1—V1iv | 3.414 (3) |
Ba4—Cl3ix | 3.4624 (8) | Li1—V1x | 3.510 (5) |
Ba4—Cl1 | 3.4927 (8) | Li1—Ba2iv | 3.790 (3) |
Ba4—Cl1ix | 3.4927 (8) | Li1—Ba2v | 3.790 (3) |
Ba4—V2ix | 3.5705 (6) | Li1—O1v | 3.870 (4) |
Ba4—V2 | 3.5705 (6) | Li1—O1iv | 3.870 (4) |
Ba4—Li2iii | 4.2801 (3) | Li1—Cl2xiii | 4.321 (4) |
Ba4—Li2xviii | 4.2802 (3) | Li1—Cl2xv | 4.321 (4) |
Ba4—Li2xv | 4.2801 (3) | Li1—Li1xii | 4.713 (8) |
Ba4—Li2 | 4.2801 (3) | Li1—Li1xiv | 4.713 (8) |
Ba4—Ba1iv | 4.8148 (3) | Li1—Li1xxii | 5.7630 (3) |
Ba4—Ba1v | 4.8148 (3) | Li2—Cl1iv | 2.4803 (6) |
V1—O1 | 1.670 (2) | Li2—Cl3iv | 2.4840 (6) |
V1—O4viii | 1.6945 (16) | Li2—Cl4iv | 2.6094 (6) |
V1—O4 | 1.6945 (16) | Li2—Li2xxiii | 2.8815 (2) |
V1—O5 | 1.802 (2) | Li2—Li2iii | 2.8815 (2) |
V1—Li1v | 3.414 (3) | Li2—Ba1iv | 3.9407 (3) |
V1—Li1iv | 3.414 (3) | Li2—Ba2iv | 4.0191 (4) |
V1—Li1xix | 3.510 (5) | Li2—Ba4vi | 4.2801 (3) |
V1—Ba3xix | 3.5317 (5) | Li2—V2iv | 5.5579 (6) |
V1—V2ix | 3.5957 (7) | Li2—V2ix | 5.5899 (6) |
V1—Cl3 | 3.6243 (9) | Li2—V2vi | 5.5899 (6) |
V1—Ba1v | 3.7288 (4) | Li2—V1iv | 5.6294 (6) |
V1—Ba1iv | 3.7288 (4) |
Symmetry codes: (i) x−1/2, y−1/2, z; (ii) x−1/2, −y+1/2, z; (iii) −x+1/2, y−1/2, −z+1; (iv) −x+1/2, −y+1/2, −z+1; (v) −x+1/2, −y−1/2, −z+1; (vi) x−1/2, y+1/2, z; (vii) −x, −y, −z+1; (viii) x, −y, z; (ix) −x+1, −y, −z+1; (x) x, y, z−1; (xi) −x+1, −y, −z; (xii) −x+1/2, −y−1/2, −z; (xiii) x+1/2, y+1/2, z; (xiv) −x+1/2, −y+1/2, −z; (xv) x+1/2, y−1/2, z; (xvi) x+1/2, y−1/2, z−1; (xvii) x+1/2, y+1/2, z−1; (xviii) −x+1, y, −z+1; (xix) x, y, z+1; (xx) −x+1/2, −y+1/2, −z+2; (xxi) −x+1/2, −y−1/2, −z+2; (xxii) x, y+1, z; (xxiii) −x+1/2, y+1/2, −z+1. |
Experimental details
Crystal data | |
Chemical formula | Ba3Li2V2O7Cl4 |
Mr | 781.58 |
Crystal system, space group | Monoclinic, C2/m |
Temperature (K) | 293 |
a, b, c (Å) | 16.1215 (14), 5.7630 (3), 14.3795 (13) |
β (°) | 90.592 (7) |
V (Å3) | 1335.90 (18) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 10.87 |
Crystal size (mm) | 0.19 × 0.15 × 0.12 |
Data collection | |
Diffractometer | Stoe IPDSII diffractometer |
Absorption correction | Numerical (X-SHAPE; Stoe & Cie, 1996) |
Tmin, Tmax | 0.141, 0.295 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 22838, 3141, 2763 |
Rint | 0.051 |
(sin θ/λ)max (Å−1) | 0.807 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.024, 0.035, 1.61 |
No. of reflections | 3141 |
No. of parameters | 106 |
Δρmax, Δρmin (e Å−3) | 1.02, −1.27 |
Computer programs: X-AREA (Stoe & Cie, 2000), X-RED (Stoe & Cie, 1996), SIR2002 (Burla et al., 2003), SHELXL97 (Sheldrick, 2008), ATOMS (Dowty, 2000), WinGX (Version 1.70.01; Farrugia, 1999).
Ba1—O3i | 2.7589 (16) | Ba3—Cl2vi | 3.3238 (5) |
Ba1—O4ii | 2.8377 (18) | Ba4—O3 | 2.8838 (16) |
Ba1—Cl2 | 3.1660 (9) | Ba4—Cl4iii | 3.4269 (4) |
Ba1—Cl1 | 3.1824 (8) | Ba4—Cl3 | 3.4624 (8) |
Ba1—Cl4 | 3.2108 (8) | Ba4—Cl1 | 3.4927 (8) |
Ba1—O5iii | 3.3067 (11) | V1—O1 | 1.670 (2) |
Ba1—Cl3iii | 3.3179 (4) | V1—O4 | 1.6945 (16) |
Ba2—O3ii | 2.7325 (16) | V1—O5 | 1.802 (2) |
Ba2—O4 | 2.8439 (16) | V2—O2 | 1.677 (2) |
Ba2—Cl2iv | 3.1971 (11) | V2—O3 | 1.6891 (16) |
Ba2—Cl4 | 3.2490 (8) | V2—O5v | 1.810 (2) |
Ba2—O2iii | 3.2616 (12) | Li1—O1vii | 1.918 (6) |
Ba2—Cl3 | 3.2759 (8) | Li1—O4ii | 1.942 (4) |
Ba2—Cl1iii | 3.3625 (4) | Li1—O2 | 2.005 (6) |
Ba3—O1v | 2.746 (2) | Li2—Cl1viii | 2.4803 (6) |
Ba3—O5v | 2.918 (2) | Li2—Cl3viii | 2.4840 (6) |
Ba3—O2 | 2.999 (2) | Li2—Cl4viii | 2.6094 (6) |
Symmetry codes: (i) x−1/2, y−1/2, z; (ii) −x+1/2, y−1/2, −z+1; (iii) −x+1/2, −y−1/2, −z+1; (iv) −x, −y, −z+1; (v) −x+1, −y, −z+1; (vi) −x+1/2, −y−1/2, −z; (vii) x, y, z−1; (viii) −x+1/2, −y+1/2, −z+1. |
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Porous crystalline structures containing large cages or channels have been widely investigated, since they are good candidates for shape-selective molecular sieves, as in the well known case of zeolites, or can exhibit interesting ionic transport properties. The title compound contains channels delimited by LiO4 and VO4 tetrahedra and shows an unusual linkage pattern of tetrahedron rings, never observed in silicates so far due to the very rare T:O ratio of 3:7 (where T is the number of cations in tetrahedral coordination and O is the number of O atoms).
The structure contains Li1O4 and VO4 tetrahedra (Fig. 1), which share corners to form eight-tetrahedra Li3V5O24 heterorings connected into infinite layers parallel to the ab plane (Fig. 2). These layers are stacked in pairs along the c direction, giving rise to puckered chains of four-tetrahedra Li2V2O12 rings parallel to b and six-tetrahedra Li2V4O12 rings within the ac plane (Fig. 3). Thus, the linkage of the LiO4 and VO4 tetrahedra produces porous LiV2O7 double layers parallel to the ab plane. The only occurrence of six-tetrahedra rings in V5+ compounds has been reported for LiZnVO4 (Capsoni et al., 2006), but in that case the central cations of the tetrahedra do not lie on the same plane. From the directedness of the tetrahedra and the ordering of the Li1 and V atoms, the six-tetrahedra Li2V4O12 rings bear a resemblance to the Al2Si4O18 rings found in ordered cordierites (Knorr et al., 1999; Malcherek et al., 2001).
Two channels can be distinguished that are parallel to the monoclinic b axis. The smaller one is delimited by the puckered Li2V2O10 chain of four-tetrahedra Li2V2O12 rings within an LiV2O7 layer and is empty. The larger one is formed by the six-tetrahedra Li2V4O18 rings and is filled by atoms Ba3 and Cl2. The interlayer space is filled by atoms Ba1, Ba2 and Ba4 and infinite chains of face-sharing Li2Cl6 octahedra. No other instance of such infinite Li2Cl6 chains has been found in the literature.
Within the largest channel, the Ba3 atoms have a planar sixfold coordination of O atoms in the ac plane (Fig. 4a). Along the direction of the channels, four Cl2 atoms surround Ba3 in a rectangular planar coordination. This is the first occurrence of a BaO6Cl4 group with a planar hexagonal arrangement of O atoms to date; the only known compound with an approaching [similar?] environment for Ba is Ba9Cu7O15Cl2 (Kipka & Müller-Buschbaum, 1976), containing a BaO6Cl2 group, where the two Cl atoms are located on opposite sides of the BaO6 plane. The displacement ellipsoid of Ba3 is elongated in the b direction, towards the Cl atoms. The other three Ba atoms fill the interlayer space and surround the Li2O6 chains. The environments of atoms Ba1 and Ba2 are very similar to each other: both are surrounded by six O atoms and five Cl atoms. However, while Ba1 is connected via O atoms to two VO4 tetrahedra of an Li2V4O18 ring, Ba2 is linked to a V2O4 tetrahedron and an Li1O4 tetrahedron of a neighbouring ring. BaO6Cl5 groups have also been observed in verplanckite (Kampf et al., 1973). On the other hand, Ba4 is surrounded by four O atoms in a rectangular planar coordination parallel to the bc plane and is also eightfold coordinated by Cl atoms. This environment is similar to that of the Ba1 atom in Ba5(Mg0.4Mn0.6)Mn(V2O7)2Cl6 (Müller-Buschbaum & Rettich, 1997). The displacement ellipsoids of Ba1, Ba2 and Ba4 are also elongated along the monoclinic b direction; within the ac plane, they all point towards the Li2Cl6 chain.
The V1O4 and V2O4 tetrahedra possess very similar bond lengths, although their connectedness is different. The V1O4 tetrahedron shares all its corners with one V2O4 and three Li1O4 tetrahedra, while two O atoms in the V2O4 tetrahedron point towards the Ba4 atom in the interlayer space. The Li1O4 tetrahedron shares all its corners solely with VO4 tetrahedra. The Li2Cl6 octahedron possesses four Li2—Cl bonds with similar lengths, pointing towards the Ba1 and Ba2 atoms, and two longer Li2—Cl4 bonds pointing towards Ba4. The equivalent isotropic displacement parameter for the Li2 atoms within the Li2Cl6 chains is twice as large as for the tetrahedrally coordinated Li1 atoms.
The displacement ellipsoids of atoms O1, O2 and O4 at the corners of the Li1O4 tetrahedron show a pronounced elongation perpendicular to the Li1—O bonds, indicating a possible rigid body rotation of the Li1O4 tetrahedron within the Li2V4O18 ring. Atoms Cl1, Cl3 and Cl4 have quasi-isotropic displacement parameters; they are sixfold coordinated by four Ba and two Li2 atoms. The displacement ellipsoid of Cl2 is strongly elongated in the a direction, with an equivalent isotropic displacement parameter almost twice as large as for the other Cl atoms, due to a weaker interatomic potential and repulsive forces from the closest anions (Fig. 4 b), rather than from a possible ionic conductivity. Atom Cl2 is tetrahedrally coordinated by four Ba atoms. There are two V2 atoms close to Cl2, but their influence is screened by atoms O2, O3 and O5 of the V2O4 tetrahedron between V2 and Cl2. These O atoms should force the largest axis of the displacement tensor of Cl2 towards the middle of the oxygen-free faces of Cl2Ba4 (parallel to a). The Cl2Ba4 tetrahedron shares an edge with a second Cl2Ba4 group along c, resulting in a short Cl2···Cl2 distance of 3.3133 (17) Å.