A quarter of a century after its synthesis and with >200 papers based on its use, `Co(CO3)0.5(OH)·0.11H2O' proves to be Co6(CO3)2(OH)8·H2O from synchrotron powder diffraction data.

The successful attempt to solve the crystal structure of Co(CO3)0.5(OH)·0.11H2O (denoted CCH), based on synchrotron powder diffraction data, leads to a drastic revision of the chemical formula to Co6(CO3)2(OH)8·H2O [hexacobalt(II) bis(carbonate) octahydroxide monohydrate] and to a hexagonal cell instead of the orthorhombic cell suggested previously [Porta et al. (1992). J. Chem. Soc. Faraday Trans. 88, 311-319]. This results in a new structure-type related to malachite involving infinite chains of [CoO6] octahedra sharing edges along a short c axis, delimiting tunnels having a three-branched star section. All reports discussing cobalt hydroxycarbonates (CCH) without any structural knowledge and especially its topotactic decomposition into Co3O4 have, as a result, to be reconsidered.

La10W2O21: an anion-deficient fluorite-related superstructure with oxide ion conduction.

The crystal structure of La10W2O21, which has to be reformulated (La5.667W0.333)LaWO14□2, is best described, on average, by a 2 × 2 × 2 anion-deficient fluorite-related superstructure cubic cell, with space group F4 3m, Z = 4, and a = 11.17932(6) Å, similar to Y7ReO14--δ. The 32 cations are distributed with lanthanum on the 4a-site, tungsten on the 4b-site, and a partial occupancy of the 24g-site by La (94%) and W. The 56 oxygen atoms occupy four 16e-sites, three of them fully and with an occupancy of 1/2 for the fourth one. Others M10W2O21 (M = Er, Y) adopt a 3 × 2 × 2 fluorite superstructure with W in octahedral sites, whereas W is mainly in tetrahedral sites in La10W2O21. Several powerful techniques such as crystal image furnace synthesis, (139)La nuclear magnetic resonance (NMR) and convergent beam electron diffraction (CBED) were used to achieve our results. Transmission electron microscopy (microdiffraction, CBED, and Tanaka patterns) brought us the real symmetry, showing that indeed classical cubic twinning along the 3-fold axis does take place. The surprising La/W mixed site is nicely confirmed by (139)La NMR. This compound exhibits interesting fast oxide ion conducting properties, comparable with LAMOX (Lacorre et al. Nature 2000, 404, 856-858) at low temperature. As opposed to many ionic conductors, no temperature structural transition is observed. Its conductivity is about 6.4 × 10(-4) S·cm(-1) at 700 °C.

Tetra-ammine-(carbonato-κ(2) O,O')cobalt(III) nitrate: a powder X-ray diffraction study.

Practical chemistry courses at universities very frequently propose the synthesis and characterization of [Co(CO3)(NH3)4]NO3, but this goal is never achieved since students only obtain the hemihydrated form. The anhydrous form can be prepared, however, and its structure is presented here. Similar to the hemihydrate form, the anhydrous phase contains the Co(III) ion in an octahedral O2N4 coordination by a chelating carbonate group and four ammine ligands. The structure reveals an intricate array of N-H⋯O hydrogen bonds involving both the chelating and the non-chelating O atoms of the carbonate ligand as hydrogen-bond acceptors of the amine H atoms, which are also involved in hydrogen-bonding inter-actions with the nitrate O atoms. The structure of the anhydrous form is close to that of the hemihydrate phase, suggesting a probable topotactic reaction with relatively small rotations and translations of the [Co(CO3)(NH3)4](+) and NO3 (-) groups during the dehydration process, which produces an unusual volume increase of 4.3%.

A new compound in kidney stones? Powder X-ray diffraction study of calcium glycinate trihydrate.

The present identification of a new compound in kidney stones is relevant in clinical practice. Here, poly[[di-µ-aqua-bis(glycinato-κ(2)N,O)calcium(II)] monohydrate], {[Ca(C2H4NO2)2(H2O)2]·H2O}n, has been identified in a possible kidney concretion, although it could be a 'false calculus' associated with Munchausen syndrome. The crystal packing is characterized by an infinite zigzag chain of Ca atoms in [Ca(OW)4O2N2] (OW is a water O atom) square antiprisms, sharing edges formed by water molecules. An uncoordinated water molecule interconnects the parallel chains in a three-dimensional hydrogen-bonding scheme. Similarities between the trihydrate and the monohydrate are described.

Decafluorocyclohex-1-ene at 4.2†K - crystal structure and theoretical analysis of weak interactions.

The crystal structure of 1,2,3,3,4,4,5,5,6,6-decafluorocyclohex-1-ene (decafluorocyclohex-1-ene, C6F10) was solved in direct space from neutron powder diffraction data previously collected at 4.2 K [Pawley, G. S. (1981). J. Appl. Cryst. 14, 357-361] and refined by energy minimization in the solid state. To optimize the positions of the 64 atoms in the monoclinic computational cell the PBESOL and hybrid PBE0 functionals were used. The crystal structure of the title compound, which is liquid at room temperature, is built of antiparallel pairs of molecules assembled into molecular columns stacked along the a axis. Dominating the crystal-building forces are weak intermolecular dispersion interactions. Bonding conditions in the structure were analysed by theoretical molecular calculations of representative next-neighbor molecular dimers carried out using dispersion-corrected density functional theory (DFT) functionals and the SCS-MP2 wavefunction method. The largest interaction energy is of the order of ∼ 21 kJ mol(-1), above the interaction energy of a benzene dimer (11.3 kJ mol(-1)) and close to that of a water dimer (20.9 kJ mol(-1)). The interaction energy for the second most stable dimer can be compared with either that of a benzene dimer or of a C-H...π hydrogen bond. The remaining five weakly interacting dimers (∼ 4.2-8.4 kJ mol(-1)) can be characterized as having stronger interactions than those of methane dimers (-2.2 kJ mol(-1)), but weaker than those of benzene molecule pairs or weak C-H...C interactions for instance.

Crystallography Open Database (COD): an open-access collection of crystal structures and platform for world-wide collaboration.

Using an open-access distribution model, the Crystallography Open Database (COD, http://www.crystallography.net) collects all known 'small molecule / small to medium sized unit cell' crystal structures and makes them available freely on the Internet. As of today, the COD has aggregated ~150,000 structures, offering basic search capabilities and the possibility to download the whole database, or parts thereof using a variety of standard open communication protocols. A newly developed website provides capabilities for all registered users to deposit published and so far unpublished structures as personal communications or pre-publication depositions. Such a setup enables extension of the COD database by many users simultaneously. This increases the possibilities for growth of the COD database, and is the first step towards establishing a world wide Internet-based collaborative platform dedicated to the collection and curation of structural knowledge.

Databases of virtual inorganic crystal structures and their applications.

Databases dedicated to predicted inorganic crystal structures are emerging fast. Possible applications are listed, from identification through the powder diffraction pattern fingerprint, leading to crystal structure determination before estimation of the cell parameters of newly synthesized real compounds, to the prediction of interesting properties of still unknown materials, allowing chemical synthesis efforts to concentrate on definite targets. The limitations of such approaches due, in some cases, to the incompleteness and poor quality of the predictions and to the lack of openly available efficient tools are discussed through examples.

Novel layered hybrid fluoroaluminate in the composition space diagram of the Al(OH)3-HguaCl-HF(aq)-EtOH system.

A composition space diagram is used to establish the stability regions of hybrid fluoroaluminates synthesized by solvothermal reactions in the Al(OH)(3)-HguaCl-HF(aq)-EtOH system. The syntheses are conducted using microwave heating at 190 degrees C for 1 h. The structures of two new guanidinium fluoroaluminates, (H(3)O)(2) x [Hgua](16) x (Al(4)F(18))(3) x H(2)O and [Hgua](2) x (Al(5)F(17)), are reported. (H(3)O)(2) x [Hgua](16) x (Al(4)F(18))(3) x H(2)O, determined from single-crystal X-ray data, consists of discrete (Al(4)F(18))(6-) polyanions, while [Hgua](2) x (Al(5)F(17)), solved from powder X-ray diffraction data in direct space, contains unprecedented Al(5)F(17) layers constructed from the intergrowth of HTB and perovskite columns. A disorder of H(2)O and H(3)O(+) is evidenced in (H(3)O)(2) x [Hgua](16) x (Al(4)F(18))(3) x H(2)O together with a disorder of guanidinium cations in the interlayer space of [Hgua](2) x (Al(5)F(17)).

Dilead(II) chromium(III) hepta-fluoride.

Single crystals of the title compound, Pb(2)CrF(7), were obtained by solid-state reaction. The monoclinic structure is isotypic with Pb(2)RhF(7) and is built up of CrF(6) (3-) octa-hedra isolated from each other, inserted in a fluorite-related matrix of PbF(6) distorted octa-hedra, and PbF(8) square anti-prisms sharing edges and corners. The seventh F atom is 'independent', connected only to three Pb atoms within FPb(3) triangles, sharing an edge and building an almost planar Pb(4)F(2) unit, so that the formula can alternatively be written as Pb(2)F(CrF(6)).

Structure determination of La18W10O57.

We report the synthesis, structure determination, and structure analysis of La(18)W(10)O(57), which presents 52.65 WO(3) mol % in the binary system La(2)O(3)-WO(3) in place of the previous reported compound: La(14)W(8)O(45), 53.3 WO(3) mol %. The structure has been determined from synchrotron and laboratory X-ray, neutron, and electron diffraction data. This tungstate crystallizes in the non-centrosymmetric hexagonal space group (no. 190) P62c, with Z = 2, a = 9.0448(1) A, c = 32.6846(3) A, and a measured density of 7.28(3) g x cm(-3). The structure consists of [WO(6)] octahedra, isolated or sometimes sharing a face, and unusual tungsten [WO(6)] trigonal prisms. This compound presents a subcell c' = c/6 = 5.45 A. Polytypism has been observed concerning this compound. Transmission electronic microscopy, ionic conductivity, and thermal expansion have been explored.

[Cu(2)(HF(2))(H(2)O)(8)][FeF(6)]·2H(2)O.

The title compound, octaaqua-(hydrogenfluorido)dicopper(II) hexa-fluoridoferrate(III) dihydrate, was synthesized under hydro-thermal conditions. The Cu atom is coordinated by one F and five O atoms within a highly distorted octa-hedron, forming dimeric [Cu(2)(H(2)O)(8)HF(2)](3+) units by edge sharing. These units are hydrogen bonded to [FeF(6)](3-) anions and to an inter-stitial water mol-ecule. The former feature Fe(3+) on a special position (). The dimeric copper units are linked to adjacent dimers by F-H⋯F hydrogen bonds. Additional O-H⋯O and O-H⋯F hydrogen bonds help to consolidate the crystal packing.

Sr(5)(VOF(5))(3)F(H(2)O)(3) refined from a non-merohedrally twinned crystal.

The title compound, penta-strontium tris-[penta-fluorido-oxido-vanadate(IV)] fluoride trihydrate, was obtained under hydro-thermal conditions. Its crystal structure has been refined from intensity data of a non-merohedrally twinned crystal. Two domains in almost equal proportions are related by a -180° rotation along the reciprocal [101]* vector. The structure may be considered as a derivative of the fluorite structure type, adopted here by SrF(2). In the title compound, fluorite-like large rods are recognized, built up from a group of 16 Sr atoms of which 6 are substituted by V atoms, leading to [Sr(10)V(6)](∞) units. These rods extend infinitely along the b axis and are inter-connected by the three water mol-ecules. Each of the water mol-ecules is shared by two different Sr atoms belonging to two different rods. The rods are also inter-connected by an 'independent' F atom in a distorted triangular [FSr(3)] coordination and by hydrogen-bonding inter-actions via donor water mol-ecules. The acceptors are either F atoms or the O atoms of the vanadyl ion, VO(2+), that is part of the [VOF(5)] isolated octa-hedron.

Crystallography Open Database - an open-access collection of crystal structures.

The Crystallography Open Database (COD), which is a project that aims to gather all available inorganic, metal-organic and small organic molecule structural data in one database, is described. The database adopts an open-access model. The COD currently contains ∼80 000 entries in crystallographic information file format, with nearly full coverage of the International Union of Crystallography publications, and is growing in size and quality.