(IUCr) Contents for Acta Crystallographica Section B Vol. 63 Part 6 (December 2007)

Acta Crystallographica Section B: Structural Science
Volume 63, Part 6 (December 2007)
Copyright (c) International Union of Crystallography 2007

research papers

Acta Cryst. (2007). B63, 805-811
[ doi:10.1107/S0108768107046654 ]

Structure determination of Mg_[3](OH)_[5]Cl.4H_[2]O (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 Mg_[3](OH)_[5]Cl.4H_[2]O, the so-called F5 phase according to 5Mg(OH)_[2].MgCl_[2].8H_[2]O in the system MgCl_[2]-MgO-H_[2]O, 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 ABO_[3]-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 ABO_[3]-type perovskite compounds were investigated in 376 ABO_[3]-type compounds.

Online 9 November 2007

Acta Cryst. (2007). B63, 819-827
[ doi:10.1107/S0108768107049385 ]

Equilibrium langbeinite-related phosphates Cs_[1+x]Ln_[x]Zr_[2-x](PO_[4])_[3] (Ln = Sm-Lu) in the melted systems Cs_[2]O-P_[2]O_[5]-LnF_[3]-ZrF_[4]

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 Cs_[2]O-P_[2]O_[5]-ZrF_[4]-LnF_[3] (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 HgI_[2]

D. Schwarzenbach, H. Birkedal, M. Hostettler and P. Fischer

Synopsis: Thermal displacement parameters in red HgI_[2] 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 AV_[3]O_[7] (A = Ca, Sr) structure

S. Prinz, K. M. Sparta and G. Roth

Synopsis: The oxovanadates AV_[3]O_[7] (A = Ca, Sr) were synthesized and studied in the temperature ranges 297 down to 100K, and 315 down to 100K 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 La_[9]Sb_[5]O_[5] structure family: structure of Pr_[9]Sb_[5]O_[5], Sm_[9]Sb_[5]O_[5] and Dy_[9]Sb_[5]O_[5]

J. Nuss and M. Jansen

Synopsis: A single crystal of Pr_[9]Sb_[5]O_[5] and reticular merohedral twinned crystals of Sm_[9]Sb_[5]O_[5] and Dy_[9]Sb_[5]O_[5] 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 (CaAl_[2]O_[4].10D_[2]O) 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 [Zn_[2]([eta]^[5]-C_[5]Me_[5])_[2]]

J. F. Van der Maelen, E. Gutierrez-Puebla, A. Monge, S. Garcia-Granda, I. Resa, E. Carmona, M. T. Fernandez-Diaz, 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. Perez, M. C. Bueso, L. Garcia, E. Perez, 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 [pi]...[pi] 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 CH_[2]BrCl and isostructural relations between CH_[2]Cl_[2], CH_[2]Br_[2] and CH_[2]BrCl

M. Podsiadlo and A. Katrusiak

Synopsis: It has been shown on a simple compound, CH_[2]BrCl, that pressure-frozen crystals are dominated by one short contact in the crystal isostructural with the CH_[2]Cl_[2] crystal, space group Pbcn, whereas temperature freezing of CH_[2]BrCl leads to the crystal isostructural with CH_[2]Br_[2], space group C2/c, with some of the intermolecular contacts electrostatically unfavourable. In both the CH_[2]BrCl 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-C_[6]H_[10](OH)_[2] and (C_[6]H_[5])_[3]PO 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 C_[6]H_[12]O_[2] 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 [gamma]-quinacridone (C_[20]H_[12]N_[2]O_[2]) with the crystal structure of [beta]-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