Acta Crystallographica Section B

Structural Science

Volume 63, Part 6 (December 2007)

Cover illustration: The cover illustration represents the high- and incommensurately modulated room-temperature phases of Na2CO3 and its reconstructed reciprocal (h2lm) layer [-Na2CO3; Dusek et al. (2003). Acta Cryst. B59, 337-352]. Main reflections (open circles) and satellites aligned along parallel lines are indicated. A comparison of the two structures represented by slices parallel to the vertical axis c illustrates their relationship [Arakcheeva & Chapuis (2005). Acta Cryst. B61, 601-607]. -Na2CO3 at 746 K (C2/m; pseudohexagonal) is shown on the left. All C and Na atoms closer than 3.12 Å are linked. The corresponding non-periodic slice of -Na2CO3 indicates how the modulation creates additional close contacts (Ivan Orlov's design is kindly acknowledged).

• research papers

research papers

Acta Cryst. (2007). B63, 805-811  [ doi:10.1107/S0108768107046654 ] Structure determination of Mg3(OH)5Cl·4H2O (F5 phase) from laboratory powder diffraction data and its impact on the analysis of problematic magnesia floors K. Sugimoto, R. E. Dinnebier and T. Schlecht Synopsis: The crystal structure with the idealized formula Mg3(OH)5Cl·4H2O, the so-called F5 phase according to 5Mg(OH)2·MgCl2·8H2O in the system MgCl2-MgO-H2O, has been solved ab initio from high-quality laboratory powder diffraction data at room temperature. The F5 phase is of technological importance as the most important binder phase in Sorel cements. Online 9 November 2007

Acta Cryst. (2007). B63, 812-818  [ doi:10.1107/S0108768107046174 ] Structural stability and formability of ABO3-type perovskite compounds H. Zhang, N. Li, K. Li and D. Xue Synopsis: On the basis of the bond-valence model and structure-map technology, the structural stability and formability of ABO3-type perovskite compounds were investigated in 376 ABO3-type compounds. Online 9 November 2007

Acta Cryst. (2007). B63, 819-827  [ doi:10.1107/S0108768107049385 ] Equilibrium langbeinite-related phosphates Cs1 + xLnxZr2 - x(PO4)3 (Ln = Sm-Lu) in the melted systems Cs2O-P2O5-LnF3-ZrF4 I. V. Ogorodnyk, V. N. Baumer, I. V. Zatovsky, N. S. Slobodyanik, O. V. Shishkin and K. V. Domasevitch Synopsis: Members of a series of langbeinite-like compounds incorporating caesium cations inside the crystal cavities have been obtained by the flux technique and have been structurally characterized. Possibilities for the formation of caesium-containing langbeinite-related phosphates in the melted system Cs2O-P2O5-ZrF4-LnF3 (Ln = La-Nd, Sm-Lu) are analyzed. Online 9 November 2007

Acta Cryst. (2007). B63, 828-835  [ doi:10.1107/S0108768107043327 ] Neutron diffraction investigation of the temperature dependence of crystal structure and thermal motions of red HgI2 D. Schwarzenbach, H. Birkedal, M. Hostettler and P. Fischer Synopsis: Thermal displacement parameters in red HgI2 measured by neutron powder diffraction are interpreted in terms of a phonon model and a mechanism for anharmonic contributions. Online 9 November 2007

Acta Cryst. (2007). B63, 836-842  [ doi:10.1107/S0108768107050550 ] Temperature dependence of the AV3O7 (A = Ca, Sr) structure S. Prinz, K. M. Sparta and G. Roth Synopsis: The oxovanadates AV3O7 (A = Ca, Sr) were synthesized and studied in the temperature ranges 297 down to 100 K, and 315 down to 100 K by means of single-crystal X-ray diffraction. Online 9 November 2007

Acta Cryst. (2007). B63, 843-849  [ doi:10.1107/S0108768107051282 ] Reticular merohedral twinning within the La9Sb5O5 structure family: structure of Pr9Sb5O5, Sm9Sb5O5 and Dy9Sb5O5 J. Nuss and M. Jansen Synopsis: A single crystal of Pr9Sb5O5 and reticular merohedral twinned crystals of Sm9Sb5O5 and Dy9Sb5O5 have been studied by single-crystal X-ray diffraction. Online 9 November 2007

Acta Cryst. (2007). B63, 850-861  [ doi:10.1107/S0108768107035136 ] Structure of calcium aluminate decahydrate (CaAl2O4·10D2O) from neutron and X-ray powder diffraction data A. N. Christensen, B. Lebech, D. Sheptyakov and J. C. Hanson Synopsis: The crystal structure of the high-alumina cement calcium aluminate hydrate is determined by means of neutron and X-ray powder diffraction on deuterated samples. Online 9 November 2007

Acta Cryst. (2007). B63, 862-868  [ doi:10.1107/S0108768107045880 ] Experimental and theoretical characterization of the Zn-Zn bond in [Zn2(5-C5Me5)2] J. F. Van der Maelen, E. Gutiérrez-Puebla, Á. Monge, S. García-Granda, I. Resa, E. Carmona, M. T. Fernández-Díaz, G. J. McIntyre, P. Pattison and H.-P. Weber Synopsis: The experimental electron density obtained from a multipole refinement of the synchrotron X-ray data for the title complex, together with theoretical ab initio calculations of the electron density at the molecular geometry obtained from neutron diffraction data provide a complete characterization of both its Zn-Zn and Zn-Cp* bonds. Online 9 November 2007

Acta Cryst. (2007). B63, 869-878  [ doi:10.1107/S0108768107050859 ] Probabilistic model-based methodology for the conformational study of cyclic systems: application to copper complexes double-bridged by phosphate and related ligands M. Kessler, J. Pérez, M. C. Bueso, L. García, E. Pérez, J. L. Serrano and R. Carrascosa Synopsis: A methodology for the conformational study of cyclic systems through the statistical analysis of torsion angles is presented. It relies on a combination of different methods based on a probabilistic model which takes into account the topological symmetry of the structures. Online 9 November 2007

Acta Cryst. (2007). B63, 879-895  [ doi:10.1107/S0108768107036270 ] Supramolecular structures in N-isonicotinoyl arylaldehydehydrazones: multiple hydrogen-bonding modes in series of geometric isomers S. M. S. V. Wardell, M. V. N. de Souza, J. L. Wardell, J. N. Low and C. Glidewell Synopsis: In N-isonicotinoyl arylaldehydehydrazones, the molecules may be linked into supramolecular structures in one, two or three dimensions by various combinations of hydrogen bonds, augmented by stacking interactions. The hydrogen-bonded structures can range between one-, two- and three-dimensional within a series of isomers differing only in the location of a single, simple substituent such as F or OMe. Online 9 November 2007

Acta Cryst. (2007). B63, 896-902  [ doi:10.1107/S0108768107037263 ] Compressed hydrogen-bond effects in the pressure-frozen chloroacetic acid R. Gajda and A. Katrusiak Synopsis: Pressure freezing of dichloroacetic acid yields a crystal structure with interesting multihalogen motifs. Online 9 November 2007

Acta Cryst. (2007). B63, 903-911  [ doi:10.1107/S0108768107044618 ] Isobaric and isochoric freezing of CH2BrCl and isostructural relations between CH2Cl2, CH2Br2 and CH2BrCl M. Podsiadlo and A. Katrusiak Synopsis: It has been shown on a simple compound, CH2BrCl, that pressure-frozen crystals are dominated by one short contact in the crystal isostructural with the CH2Cl2 crystal, space group Pbcn, whereas temperature freezing of CH2BrCl leads to the crystal isostructural with CH2Br2, space group C2/c, with some of the intermolecular contacts electrostatically unfavourable. In both the CH2BrCl forms the Cl and Br atoms are disordered. Online 9 November 2007

Acta Cryst. (2007). B63, 912-925  [ doi:10.1107/S0108768107054699 ] An unexpected co-crystal with a variable degree of order: 1:1 rac-1,2-cyclohexanediol/triphenylphosphine oxide M. A. Siegler, Y. Fu, G. H. Simpson, D. P. King, S. Parkin and C. P. Brock Synopsis: A 1:1 co-crystal of rac-1,2-C6H10(OH)2 and (C6H5)3PO has been found that is unusual because there are no strong interactions between the two different kinds of molecules, which are segregated into layers. The degree of ordering of enantiomers within and between the C6H12O2 layers seems to depend on the solvent from which the crystal is grown. Online 9 November 2007

Acta Cryst. (2007). B63, 926-932  [ doi:10.1107/S0108768107050823 ] Rietveld refinement of a wrong crystal structure C. Buchsbaum and M. U. Schmidt Synopsis: The Rietveld refinement of -quinacridone (C20H12N2O2) with the crystal structure of -quinacridone gives a smooth difference curve and a reasonable looking crystal structure; nevertheless, molecular conformation, packing and lattice parameters are definitively wrong. This example shows that a successful Rietveld refinement is not always final proof of the crystal structure. Online 9 November 2007

Acta Cryst. (2007). B63, 933-940  [ doi:10.1107/S0108768107051336 ] Monitoring structural transformations in crystals. 11. Yang photocyclizations - one type of reaction, but diversity of structural changes I. Turowska-Tyrk, J. Bakowicz and J. R. Scheffer Synopsis: Variations in the cell constants, the product content in the crystal, the mutual orientation of directly reacting atoms, the orientation of molecules and changes in the hydrogen bonds brought about by an intramolecular photochemical reaction were monitored using X-ray diffraction. The studies provide detailed information about the course of the Yang photocyclization reactions in crystals. Online 9 November 2007

Copyright © International Union of Crystallography
IUCr Webmaster