Ca 5 Zr 3 F 22

Single crystals of Ca(5)Zr(3)F(22), penta-calcium trizirconium docosafluoride, were obtained unexpectedly by solid-state reaction between CaF(2) and ZrF(4) in the presence of AgF. The structure of the title compound is isotypic with that of Sr(5)Zr(3)F(22) and can be described as being composed of layers with composition [Zr(3)F(20)](8-) made up from two different [ZrF(8)](4-) square anti-prisms (one with site symmetry 2) by corner-sharing. The layers extending parallel to the (001) plane are further linked by Ca(2+) cations, forming a three-dimensional network. Amongst the four crystallographically different Ca(2+) ions, three are located on twofold rotation axes. The Ca(2+) ions exhibit coordination numbers ranging from 8 to 12, depending on the cut off, with very distorted fluorine environments. Two of the Ca(2+) ions occupy inter-stices between the layers whereas the other two are located in void spaces of the [Zr(3)F(20)](8-) layer and alternate with the two Zr atoms along [010]. The crystal under investigation was an inversion twin.

Single crystals of Ca 5 Zr 3 F 22 , pentacalcium trizirconium docosafluoride, were obtained unexpectedly by solid-state reaction between CaF 2 and ZrF 4 in the presence of AgF. The structure of the title compound is isotypic with that of Sr 5 Zr 3 F 22 and can be described as being composed of layers with composition [Zr 3 F 20 ] 8À made up from two different [ZrF 8 ] 4À square antiprisms (one with site symmetry 2) by corner-sharing. The layers extending parallel to the (001) plane are further linked by Ca 2+ cations, forming a threedimensional network. Amongst the four crystallographically different Ca 2+ ions, three are located on twofold rotation axes. The Ca 2+ ions exhibit coordination numbers ranging from 8 to 12, depending on the cut off, with very distorted fluorine environments. Two of the Ca 2+ ions occupy interstices between the layers whereas the other two are located in void spaces of the [Zr 3 F 20 ] 8À layer and alternate with the two Zr atoms along [010]. The crystal under investigation was an inversion twin.

Crystal data
The orthorhombic structure of the title compound is isotypic with that of Sr 5 Zr 3 F 22 reported by Le Bail (1996). As with this latter, the structure of Ca 5 Zr 3 F 22 has also been determined from an inversion twinned crystal although the crystals were grown in very different ways. Figure

S2. Experimental
Single crystals of Ca 5 Zr 3 F 22 were unexpectedly obtained from an equimolar mixture of AgF, CaF 2 and ZrF 4 heated at 873 K in a sealed platinum tube during the study of the phase diagram of the ternary system AgF-CaF 2 -ZrF 4 . After heating at this temperature for 24 h, the sample was cooled to room temperature at the rate of 5 K . h -1 for the first 24 h and then by switching the power off. Small platelet like crystals of Ca 5 Zr 3 F 22 could have been extracted from the batch. Both AgF and CaF 2 were commercial products whereas ZrF 4 was prepared by direct fluorination of ZrO 2 under pure fluorine gas flow at 873 K with intermediate grindings. CaF 2 was also heated at 873 K overnight under fluorine gas flow prior to use.

S3. Refinement
The highest residual peak in the final difference Fourier map was located 0.04 Å from atom Zr2 and the deepest hole was located 1.05 Å from atom F9.

Special details
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 F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 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 (Å 2 )
x y z U iso */U eq  (7)