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Lithium barium hexa­fluoro­aluminate (LBAF), LiBaAlF6, is a new member of the large family of compounds of formula LiAIIBIIIF6. These materials display a variety of structures depending on the sizes of the A and B cations. LiBaAlF6, which is isomorphous with LiBaCoF6, belongs to the monoclinic P21/c subset and has a three-dimensional network structure consisting of distorted LiF43- tetra­hedra corner-sharing with AlF63- octa­hedra and BaF12 polyhedra. All of the atoms reside on general positions. An analysis of the ionic radii of the A cations versus formula volumes for the known members of the family yields a structure map that reasonably segregates the compounds by space group. The data obtained are thus suitable for predicting new isomorphic crystal structures.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270108017538/sq3143sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270108017538/sq3143Isup2.hkl
Contains datablock I

Comment top

It is often possible to predict a new structure by analogy. The LiAIIBIIIF6 family is one of the well studied sets of fluoride structures. The fluorides with cation pairs (AIIBIII) PdAl (Bachmann & Mueller, 1993), YbAl (Koehler, 1999), CaAl (Bolotina et al., 1993), CaCr (Rupp et al., 1993), CdCo, CaNi, CaCo and SrNi (Fleischer & Hoppe, 1982) and SrAl (Schaffers & Keszler, 1991) crystallize in space group P3c. These crystals have layered structures in which face-sharing octahedra BIIIF63- and LiF65- alternate with layers of divalent cations. Both the first and second coordination environments of AII are octahedral. Distorted anionic 36 grids are located in perpendicular planes (001) and (110). LiSmAlF6 is characterized by the hexagonal space group P6322 (Koehler & Mueller, 1991). In contrast with those crystals with a P3c structure, the SmF64- polyhedron is prismatic rather than octahedral.

A decrease in the radius of the divalent cation results in a change of symmetry to tetragonal P42/mnn in the case of LiMgCoF6, LiNiCoF6 and LiZnCoF6 (Fleischer & Hoppe, 1982). All cations in these crystals have octahedral coordination environments, and the Li and Mg atoms are located in common sites. Increasing the radii of the di- and trivalent cations also causes changes in the space group. Fluorides with cation pairs AIIBIII such as SrCo, SrFe and BaCo (Fleischer & Hoppe, 1982) and BaCr (Babel, 1974) are characterized by the monoclinic space group P21/c. Despite their identical space group and the closely similar atom positions in their unit cells, the structure of the strontium-containing fluorides differs from that of the barium fluorides. The coordination environment of Sr is a distorted square antiprism, while the Li atoms have an octahedral environment. In contrast, the Ba atoms are characterized by a coordination number of 12 and Li atoms have a coordination number of 4 in the barium fluorides. The tetrahedral Li-centred polyhedron is distorted due to the presence of one additional longer bond (ca. 2.65 Å) with an F atom of the second coordination sphere.

The previously unreported title compound, LiBaAlF6, (I), belongs to the monoclinic P21/c subset of this family. The three-dimensional network structure, consisting of Li-centred distorted tetrahedra corner-sharing with Al-centred octahedra and Ba-centred polyhedra, is analogous to that of LiBaCoF6 (Fig. 1). The large Ba polyhedron (distorted bicapped pentagonal prism) compresses the lithium coordination environment and transforms it from octahedral to tetrahedral. It might seem that the small volume of the Al polyhedra could provoke an increase of the Li coordination environment up to octahedral, but this is not the case.

The dependence of the formula volumes on the Shannon (1976) radii of divalent cations with coordination number 6 for the known LiAIIBIIIF6 phases (Fig. 2a) shows a fairly good segregation of the different structures by space group. One can see a real possibility of structure prediction for some new crystals by analogy with known isomorphic structures. Nevertheless, there are some areas of overlap, making it difficult to predict the LiBaAlF6 structure based on these data alone. Moreover, the structures of LiSrNiF6 and LiSrCoF6 differ despite the small differences in the Ni and Co radii.

It is possible to calculate the radii in these structures by a different method. All F—F distances in the coordination polyhedra were averaged and halved in order to estimate the anionic fluoride radius. Subtracting the anionic radius obtained in this manner from the mean cation–anion distance allows one to determine the cationic radius. There is good agreement between the Shannon ionic radii and the calculated values in the case of trivalent cation octahedra (Table 1). In the case of polyhedra with divalent cations, the situation is different. The anionic radii of fluoride found via the F—F distances are larger than the tabulated values, making the cationic radii smaller than the tabulated ones. This indicates that the divalent cations pull the fluoride anions together more weakly than do the trivalent cations. According to the Shannon data, the NiIII ionic radius is larger than those of CoIII and FeIII, which does not correlate with their relative positions in the periodic table. The increase of di- and trivalent cation radii in LiAIIBIIIF6 crystals is accompanied by a gradual increase in the crystal [unit-cell?] volume and causes a symmetry change. Trigonal symmetry is the most prevalent for the fluorides considered here. In compounds with a small BIII radius and a rather large AII radius, a reorganization from a trigonal structure into a hexagonal one (LiSmAlF6) may take place. A small increase in the trivalent cation radius when passing from LiSrNiF6 to LiSrCoF6 causes a significant lowering of symmetry down to monoclinic. This may mean that the gradual increase in the size of the trivalent cation octahedron leads to compression of the strained divalent cation polyhedron. When the difference between the tabulated radius of SrII and the calculated radius reaches a maximum (0.48 Å), as in the case of LiSrNiF6, the structure becomes reorganized back to trigonal. The increase of the AII radius in the monoclinic structures (LiSrCoF6 LiBaCoF6) causes a reorganization of the structures of the Li, Sr and Ba coordination polyhedra without a change of space group. The analogous structure map with our calculated AII radii plotted against formula volume is shown in Fig. 2(b). For a small cationic radius the volume increases sharply with increasing radius. Once the cationic radius becomes similar to the anionic one, realignment of the unit cell occurs without a significant volume change. This map also provides good segregation of space groups.

In conclusion, the structure determination of LiBaAlF6 completes a data set for the construction of correlations between ionic radii, unit-cell parameters and space groups for crystals in the LiAIIBIIIF6 family, making it possible to predict reliably in many cases the structure type of new isomorphic crystals of similar compounds.

Experimental top

Lithium barium hexafluoroaluminate, LiBaAlF6 (LBAF), was grown from the melt by the Bridgman method in quartz crucibles. Double fluorides of 99.99% purity were used as starting reagents. LiBaAlF6 melts congruently at 1113–1133 K. The partial AlF3 pressure was determined to be ~1 bar at this temperature (1 bar = 100 000 Pa). Because of the high volatility of this component, an excess ~2 wt.% of AlF3 was added to the original composition. Crystal growth was carried out in a graphite container placed inside the silica ampoule. All operations were carried out in a dry box to avoid oxygen-containing impurities. To suppress decomposition, CF4 was added to the reactor. The experiments were carried at a surplus pressure [Please state]. The axial temperature gradient was 10–20 K cm-1 and the ampoule pulling rate varied from 0.5 to 5 mm d-1. The crystal composition was analyzed using an EDS microprobe to 0.5% coincidence in composition.

Refinement top

Analysis of the X-ray data using the XPREP program (Bruker, 2004) indicated three possible space groups, P21/c, Pc and P21. The structure was refined in P21/c to a final wR2 = 0.0352, R1 = 0.0141 for 1607 reflections (1638 unique; Rint = 0.0173), 83 parameters. The corresponding data for the Pc group are: 2319 unique reflections, Rint = 0.0156, wR2 = 0.0335, R1 = 0.0128 for 2260 reflections, 164 parameters; the Flack (1983) parameter was 0.22 (3). There is a problem in the latter case with the anisotropic refinement of atom Li1. The TWIN, BASF and ISOR instructions (SHELXTL; Sheldrick, 2008) for Li1 resulted in wR2 = 0.0319, R1 = 0.0124, 165 parameters, twinning 0.52:0.48. The R1 value for the P21 space group is larger than either of the other cases. Therefore, the crystal structure corresponds to either the centrosymmetric P21/c group or noncentrosymmetric Pc group. By analogy with the case of LiBaCoF6, we chose the P21/c space group.

Computing details top

Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXTL (Version 6.12; Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Version 6.12; Sheldrick, 2008); molecular graphics: BS (Ozawa & Kang, 2004); software used to prepare material for publication: SHELXTL (Version 6.12; Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. A polyhedral cell representation of the title compound along c. AlF6 polyhedra are light-coloured, LiF4 polyhedra are dark-coloured and Ba cations are shown as circles. The fifth Li—F contacts are shown as thick lines.
[Figure 2] Fig. 2. (a) A structure map showing the dependence of the formula volumes V/Z on the Shannon (1976) radii of AII cations of coordination number 6, and the distribution of the space groups of known LiAIIBIIIF6 structures. (b) A structure map showing the dependence of the formula volumes V/Z on the calculated radii of AII cations of varied coordination number (as shown in Table 1), and the distribution of the space groups.
Lithium barium hexafluoridoaluminate top
Crystal data top
LiBaAlF6F(000) = 504
Mr = 285.26Dx = 4.098 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 4185 reflections
a = 5.3372 (10) Åθ = 2.4–32.6°
b = 10.150 (2) ŵ = 8.82 mm1
c = 8.535 (2) ÅT = 296 K
β = 90.34 (3)°Prism, colourless
V = 462.35 (17) Å30.22 × 0.18 × 0.18 mm
Z = 4
Data collection top
Bruker Nonius X8-APEX CCD area-detector
diffractometer
1638 independent reflections
Radiation source: fine-focus sealed tube1607 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.017
Detector resolution: 25 pixels mm-1θmax = 32.6°, θmin = 3.1°
ϕ scansh = 74
Absorption correction: multi-scan
(SADABS; Bruker, 2004)
k = 1515
Tmin = 0.159, Tmax = 0.210l = 1212
4624 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.014 w = 1/[σ2(Fo2) + (0.0163P)2 + 0.1651P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.035(Δ/σ)max = 0.001
S = 1.17Δρmax = 1.48 e Å3
1638 reflectionsΔρmin = 0.90 e Å3
83 parametersExtinction correction: SHELXTL (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.0271 (8)
Crystal data top
LiBaAlF6V = 462.35 (17) Å3
Mr = 285.26Z = 4
Monoclinic, P21/cMo Kα radiation
a = 5.3372 (10) ŵ = 8.82 mm1
b = 10.150 (2) ÅT = 296 K
c = 8.535 (2) Å0.22 × 0.18 × 0.18 mm
β = 90.34 (3)°
Data collection top
Bruker Nonius X8-APEX CCD area-detector
diffractometer
1638 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2004)
1607 reflections with I > 2σ(I)
Tmin = 0.159, Tmax = 0.210Rint = 0.017
4624 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.01483 parameters
wR(F2) = 0.0350 restraints
S = 1.17Δρmax = 1.48 e Å3
1638 reflectionsΔρmin = 0.90 e Å3
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
xyzUiso*/Ueq
Al10.76102 (9)0.08866 (4)0.23055 (5)0.00874 (9)
F10.61125 (19)0.24917 (9)0.25861 (11)0.01352 (18)
F20.6713 (2)0.10245 (11)0.03123 (12)0.0192 (2)
F30.89025 (19)0.07589 (10)0.20663 (13)0.0180 (2)
F40.8278 (2)0.08905 (11)0.43998 (12)0.01721 (19)
F51.0623 (2)0.15799 (12)0.19808 (14)0.0207 (2)
F60.47012 (17)0.00991 (10)0.28925 (12)0.01348 (18)
Li10.7606 (6)0.4150 (3)0.3261 (4)0.0161 (6)
Ba10.297669 (16)0.312656 (9)0.004198 (10)0.01139 (5)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Al10.00820 (19)0.00833 (19)0.00971 (19)0.00031 (15)0.00053 (15)0.00109 (15)
F10.0162 (4)0.0093 (4)0.0151 (4)0.0019 (3)0.0000 (3)0.0005 (3)
F20.0258 (5)0.0219 (5)0.0098 (4)0.0025 (4)0.0009 (4)0.0007 (4)
F30.0149 (4)0.0135 (5)0.0256 (5)0.0042 (4)0.0050 (4)0.0016 (4)
F40.0176 (5)0.0211 (5)0.0129 (4)0.0021 (4)0.0041 (3)0.0026 (4)
F50.0123 (5)0.0241 (5)0.0258 (5)0.0052 (4)0.0022 (4)0.0074 (4)
F60.0103 (4)0.0125 (4)0.0176 (4)0.0031 (3)0.0023 (3)0.0026 (3)
Li10.0144 (13)0.0195 (15)0.0143 (13)0.0021 (11)0.0002 (10)0.0036 (10)
Ba10.01137 (7)0.01273 (6)0.01006 (6)0.00040 (3)0.00115 (4)0.00215 (3)
Geometric parameters (Å, º) top
Al1—F11.8311 (11)F2—Li1vii1.826 (3)
Al1—F21.7702 (12)Li1—F11.948 (3)
Al1—F31.8189 (11)Li1—F2ii1.826 (3)
Al1—F41.8206 (12)Li1—F3viii1.888 (3)
Al1—F51.7787 (12)Li1—F6ix1.843 (3)
Al1—F61.8192 (11)Li1—F5viii2.649 (3)
Al1—Li1i3.142 (3)Li1—Al1viii3.142 (3)
Al1—Ba1ii3.5556 (11)Li1—Ba1ii3.715 (3)
Al1—Ba1iii3.6166 (7)Li1—Ba1x3.959 (3)
Al1—Ba1iv3.8187 (12)Li1—Ba1iv3.977 (3)
Al1—Ba13.8679 (9)Li1—Ba1v4.115 (3)
F5—Ba1v2.6086 (12)Ba1—F1vii2.7623 (13)
F5—Li1i2.649 (3)Ba1—F12.8086 (13)
F5—Ba1iv2.9075 (15)Ba1—F22.9285 (12)
F4—Ba1iv2.7512 (12)Ba1—F3ix2.8994 (13)
F4—Ba1iii2.9239 (12)Ba1—F3vi3.1619 (12)
F4—Ba1ii3.0527 (12)Ba1—F4xi2.7512 (12)
F1—Ba1ii2.7623 (13)Ba1—F4ix2.9239 (12)
F3—Li1i1.888 (3)Ba1—F4vii3.0527 (12)
F3—Ba1iii2.8994 (13)Ba1—F5xii2.6086 (12)
F3—Ba1vi3.1619 (12)Ba1—F5xi2.9075 (15)
F6—Li1iii1.843 (3)Ba1—F6vii2.7342 (11)
F6—Ba1ii2.7342 (11)Ba1—F6ix2.9371 (12)
F6—Ba1iii2.9371 (12)
F2—Al1—F593.36 (6)F4xi—Ba1—F5xi52.80 (4)
F2—Al1—F393.75 (6)F1vii—Ba1—F5xi66.54 (3)
F5—Al1—F390.11 (6)F1—Ba1—F5xi166.05 (3)
F2—Al1—F694.18 (6)F3ix—Ba1—F5xi125.11 (3)
F5—Al1—F6172.16 (6)F5xii—Ba1—F4ix111.25 (4)
F3—Al1—F687.27 (5)F6vii—Ba1—F4ix63.62 (3)
F2—Al1—F4173.55 (6)F4xi—Ba1—F4ix58.34 (4)
F5—Al1—F488.87 (6)F1vii—Ba1—F4ix118.81 (3)
F3—Al1—F492.30 (5)F1—Ba1—F4ix103.31 (3)
F6—Al1—F483.85 (6)F3ix—Ba1—F4ix53.58 (3)
F2—Al1—F186.53 (5)F5xi—Ba1—F4ix87.13 (3)
F5—Al1—F193.68 (6)F5xii—Ba1—F280.90 (4)
F3—Al1—F1176.18 (6)F6vii—Ba1—F2107.51 (3)
F6—Al1—F188.91 (5)F4xi—Ba1—F2154.07 (3)
F4—Al1—F187.29 (5)F1vii—Ba1—F258.60 (3)
F2—Al1—Li1i96.43 (7)F1—Ba1—F250.92 (3)
F5—Al1—Li1i57.43 (7)F3ix—Ba1—F2117.13 (3)
F3—Al1—Li1i32.73 (7)F5xi—Ba1—F2115.83 (3)
F6—Al1—Li1i119.44 (7)F4ix—Ba1—F2147.42 (3)
F4—Al1—Li1i89.87 (7)F5xii—Ba1—F6ix103.45 (4)
F1—Al1—Li1i151.03 (7)F6vii—Ba1—F6ix79.12 (4)
F2—Al1—Ba1ii115.07 (5)F4xi—Ba1—F6ix104.67 (3)
F5—Al1—Ba1ii128.60 (5)F1vii—Ba1—F6ix110.79 (3)
F3—Al1—Ba1ii126.73 (4)F1—Ba1—F6ix56.29 (3)
F6—Al1—Ba1ii49.07 (4)F3ix—Ba1—F6ix50.95 (3)
F4—Al1—Ba1ii59.15 (4)F5xi—Ba1—F6ix130.39 (3)
F1—Al1—Ba1ii50.03 (3)F4ix—Ba1—F6ix49.03 (3)
Li1i—Al1—Ba1ii145.89 (6)F2—Ba1—F6ix99.48 (3)
F2—Al1—Ba1iii129.71 (4)F5xii—Ba1—F4vii139.54 (4)
F5—Al1—Ba1iii119.06 (5)F6vii—Ba1—F4vii49.33 (3)
F3—Al1—Ba1iii52.65 (4)F4xi—Ba1—F4vii133.67 (4)
F6—Al1—Ba1iii53.85 (4)F1vii—Ba1—F4vii51.07 (3)
F4—Al1—Ba1iii53.44 (4)F1—Ba1—F4vii70.44 (3)
F1—Al1—Ba1iii124.60 (4)F3ix—Ba1—F4vii110.55 (4)
Li1i—Al1—Ba1iii74.65 (6)F5xi—Ba1—F4vii101.60 (4)
Ba1ii—Al1—Ba1iii75.160 (18)F4ix—Ba1—F4vii85.93 (3)
F2—Al1—Ba1iv139.88 (5)F2—Ba1—F4vii67.72 (3)
F5—Al1—Ba1iv46.84 (4)F6ix—Ba1—F4vii59.78 (3)
F3—Al1—Ba1iv91.49 (4)F5xii—Ba1—F3vi75.60 (4)
F6—Al1—Ba1iv125.81 (4)F6vii—Ba1—F3vi103.04 (3)
F4—Al1—Ba1iv42.03 (4)F4xi—Ba1—F3vi82.91 (3)
F1—Al1—Ba1iv90.75 (4)F1vii—Ba1—F3vi65.61 (3)
Li1i—Al1—Ba1iv68.53 (6)F1—Ba1—F3vi116.82 (3)
Ba1ii—Al1—Ba1iv92.661 (19)F3ix—Ba1—F3vi132.13 (3)
Ba1iii—Al1—Ba1iv83.556 (18)F5xi—Ba1—F3vi55.43 (3)
F2—Al1—Ba145.97 (4)F4ix—Ba1—F3vi138.57 (3)
F5—Al1—Ba1105.40 (4)F2—Ba1—F3vi72.82 (3)
F3—Al1—Ba1136.50 (4)F6ix—Ba1—F3vi172.30 (3)
F6—Al1—Ba181.47 (4)F4vii—Ba1—F3vi115.94 (3)
F4—Al1—Ba1127.58 (4)F2ii—Li1—F6ix112.68 (16)
F1—Al1—Ba142.61 (3)F2ii—Li1—F3viii114.19 (16)
Li1i—Al1—Ba1140.41 (6)F6ix—Li1—F3viii123.53 (17)
Ba1ii—Al1—Ba173.583 (17)F2ii—Li1—F195.21 (15)
Ba1iii—Al1—Ba1135.275 (17)F6ix—Li1—F191.32 (14)
Ba1iv—Al1—Ba1128.778 (19)F3viii—Li1—F1113.63 (16)
Al1—F5—Ba1v140.91 (6)F2ii—Li1—F5viii105.08 (14)
Al1—F5—Li1i88.12 (8)F6ix—Li1—F5viii73.12 (11)
Ba1v—F5—Li1i109.72 (8)F3viii—Li1—F5viii65.81 (10)
Al1—F5—Ba1iv106.66 (6)F1—Li1—F5viii157.95 (15)
Ba1v—F5—Ba1iv107.54 (4)F2ii—Li1—Al1viii114.76 (14)
Li1i—F5—Ba1iv90.73 (7)F6ix—Li1—Al1viii99.54 (12)
Al1—F4—Ba1iv111.67 (6)F3viii—Li1—Al1viii31.38 (7)
Al1—F4—Ba1iii96.56 (4)F1—Li1—Al1viii140.41 (14)
Ba1iv—F4—Ba1iii121.66 (4)F5viii—Li1—Al1viii34.45 (5)
Al1—F4—Ba1ii90.05 (5)F2ii—Li1—Ba1ii50.89 (9)
Ba1iv—F4—Ba1ii133.67 (4)F6ix—Li1—Ba1ii95.73 (12)
Ba1iii—F4—Ba1ii94.07 (3)F3viii—Li1—Ba1ii138.60 (13)
Al1—F1—Li1129.01 (11)F1—Li1—Ba1ii46.49 (7)
Al1—F1—Ba1ii99.44 (4)F5viii—Li1—Ba1ii148.13 (11)
Li1—F1—Ba1ii102.75 (10)Al1viii—Li1—Ba1ii162.71 (10)
Al1—F1—Ba1111.20 (5)F2ii—Li1—Ba1119.40 (13)
Li1—F1—Ba1105.72 (9)F6ix—Li1—Ba148.12 (8)
Ba1ii—F1—Ba1106.13 (4)F3viii—Li1—Ba1122.73 (13)
Al1—F3—Li1i115.89 (11)F1—Li1—Ba144.94 (7)
Al1—F3—Ba1iii97.43 (5)F5viii—Li1—Ba1115.21 (10)
Li1i—F3—Ba1iii116.96 (11)Al1viii—Li1—Ba1124.30 (9)
Al1—F3—Ba1vi129.98 (5)Ba1ii—Li1—Ba172.35 (6)
Li1i—F3—Ba1vi100.89 (10)F2ii—Li1—Ba1x136.95 (14)
Ba1iii—F3—Ba1vi94.46 (3)F6ix—Li1—Ba1x37.41 (7)
Al1—F6—Li1iii130.61 (11)F3viii—Li1—Ba1x86.22 (11)
Al1—F6—Ba1ii100.76 (5)F1—Li1—Ba1x111.27 (12)
Li1iii—F6—Ba1ii118.42 (10)F5viii—Li1—Ba1x47.26 (6)
Al1—F6—Ba1iii96.14 (4)Al1viii—Li1—Ba1x63.86 (6)
Li1iii—F6—Ba1iii104.03 (11)Ba1ii—Li1—Ba1x132.55 (8)
Ba1ii—F6—Ba1iii100.88 (4)Ba1—Li1—Ba1x68.34 (5)
Al1—F2—Li1vii147.48 (12)F2ii—Li1—Ba1iv76.62 (10)
Al1—F2—Ba1108.27 (5)F6ix—Li1—Ba1iv170.18 (14)
Li1vii—F2—Ba1100.17 (11)F3viii—Li1—Ba1iv51.32 (8)
F5xii—Ba1—F6vii170.84 (3)F1—Li1—Ba1iv84.46 (10)
F5xii—Ba1—F4xi84.42 (4)F5viii—Li1—Ba1iv108.29 (9)
F6vii—Ba1—F4xi86.42 (4)Al1viii—Li1—Ba1iv78.47 (6)
F5xii—Ba1—F1vii129.85 (4)Ba1ii—Li1—Ba1iv87.80 (6)
F6vii—Ba1—F1vii55.43 (3)Ba1—Li1—Ba1iv125.26 (8)
F4xi—Ba1—F1vii119.14 (4)Ba1x—Li1—Ba1iv136.99 (8)
F5xii—Ba1—F170.03 (4)F2ii—Li1—Ba1v143.35 (13)
F6vii—Ba1—F1117.93 (3)F6ix—Li1—Ba1v103.96 (12)
F4xi—Ba1—F1140.85 (3)F3viii—Li1—Ba1v38.90 (8)
F1vii—Ba1—F1100.00 (3)F1—Li1—Ba1v82.52 (10)
F5xii—Ba1—F3ix61.61 (4)F5viii—Li1—Ba1v86.15 (8)
F6vii—Ba1—F3ix115.70 (3)Al1viii—Li1—Ba1v57.93 (5)
F4xi—Ba1—F3ix73.06 (4)Ba1ii—Li1—Ba1v125.71 (8)
F1vii—Ba1—F3ix161.59 (3)Ba1—Li1—Ba1v84.35 (6)
F1—Ba1—F3ix68.84 (3)Ba1x—Li1—Ba1v75.70 (5)
F5xii—Ba1—F5xi115.13 (4)Ba1iv—Li1—Ba1v66.74 (5)
F6vii—Ba1—F5xi58.33 (3)
Symmetry codes: (i) x+2, y1/2, z+1/2; (ii) x, y+1/2, z+1/2; (iii) x+1, y1/2, z+1/2; (iv) x+1, y+1/2, z+1/2; (v) x+1, y, z; (vi) x+1, y, z; (vii) x, y+1/2, z1/2; (viii) x+2, y+1/2, z+1/2; (ix) x+1, y+1/2, z+1/2; (x) x+1, y+1, z; (xi) x1, y+1/2, z1/2; (xii) x1, y, z.

Experimental details

Crystal data
Chemical formulaLiBaAlF6
Mr285.26
Crystal system, space groupMonoclinic, P21/c
Temperature (K)296
a, b, c (Å)5.3372 (10), 10.150 (2), 8.535 (2)
β (°) 90.34 (3)
V3)462.35 (17)
Z4
Radiation typeMo Kα
µ (mm1)8.82
Crystal size (mm)0.22 × 0.18 × 0.18
Data collection
DiffractometerBruker Nonius X8-APEX CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 2004)
Tmin, Tmax0.159, 0.210
No. of measured, independent and
observed [I > 2σ(I)] reflections
4624, 1638, 1607
Rint0.017
(sin θ/λ)max1)0.758
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.014, 0.035, 1.17
No. of reflections1638
No. of parameters83
Δρmax, Δρmin (e Å3)1.48, 0.90

Computer programs: APEX2 (Bruker, 2004), SAINT (Bruker, 2004), SHELXTL (Version 6.12; Sheldrick, 2008), BS (Ozawa & Kang, 2004).

Comparison of the ionic radii and formula volumes of LiAIIBIIIF6 compounds top
V/Z (Å3)M2+ (Shannon)M2+ (calculated)LiAlNiCoFeCr
LiMgCoF6P42/mnn95.920.720.5890.5890.565
LiNiCoF696.420.690.5900.5900.559
LiZnCoF697.980.740.5940.5940.569
LiPdAlF6P3c97.840.860.6410.5830.530
LiCdCoF6106.610.950.6600.5930.548
LiCaAlF6104.671.000.6690.5890.528
LiCaNiF6108.041.000.6670.5950.545
LiCaCoF6110.291.000.6710.6000.548
LiCaCrF6110.301.00.6680.5940.558
LiYbAlF6108.631.020.6870.5910.529
LiSrAlF6113.461.180.7110.5920.527
LiSrNiF6117.571.180.6970.6110.544
LiSmAlF6P6322116.231.200.8400.5910.529
LiSrCoF6P21/c117.931.261.09610.6000.564
LiSrFeF6119.071.261.10810.6050.567
LiBaAlF6115.591.611.39020.36230.530
LiBaCoF6119.181.611.39220.36030.556
LiBaCrF6120.681.611.39120.35930.558
rcat., av.0.5950.5290.5450.558
0.363
ran., av.1.631.431.281.321.351.361.35
1.481,21.533
Notes: (1) Sr coordination number is 8. (2) Ba coordination number is 12. (3) Li coordination number is 4. Li+, Al3+, Ni3+, Co3+, Fe3+ and Cr3+ Shannon radii for an octahedral environment are, respectively, 0.76 (0.594 for tetrahedral coordination environment), 0.535, 0.56, 0.545, 0.55 and 0.615 Å.
 

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