Structural Science

 

Acta Cryst. (2009). B65, 249-268  [ doi:10.1107/S0108768109015614 ]

A non-mathematical introduction to the superspace description of modulated structures

T. Wagner and A. Schönleber

Synopsis: The basic principles of handling and describing modulated structures with the superspace formalism are given in a non-mathematical way. They are illustrated using the crystal structure of (6R,7aS)-6-(tert-butyl-dimethylsilanyloxy)-1-hydroxy-2-phenyl-5,6,7,7a-tetrahydropyrrolizin-3-one, C₁₉H₂₇NO₃Si.

Online 19 May 2009

 

Acta Cryst. (2009). B65, 269-290  [ doi:10.1107/S0108768109011355 ]

Complex ceramic structures. I. Weberites

L. Cai and J. C. Nino

Synopsis: This article focuses on weberite ceramics. The structural features of weberite, its relationship to the fluorite and the pyrochlore structures, and some weberite ceramics with interesting properties are discussed.

Online 19 May 2009

 

Acta Cryst. (2009). B65, 291-299  [ doi:10.1107/S0108768109011057 ]

Structures of K_0.05Na_0.95NbO₃ (50-300 K) and K_0.30Na_0.70NbO₃ (100-200 K)

N. Zhang, A. M. Glazer, D. Baker and P. A. Thomas

Synopsis: The structures of K_xNa_1 - xNbO₃ (x = 0.05, x = 0.3) at low temperatures have been determined by neutron powder diffraction studies. The phase-coexistence region at the transition between rhombohedral and monoclinic phases was also identified, consistent with a first-order phase boundary.

Online 19 May 2009

 

Acta Cryst. (2009). B65, 300-307  [ doi:10.1107/S0108768109012828 ]

Structures of the ZrZn₂₂ family: suprapolyhedral nanoclusters, methods of self-assembly and superstructural ordering

G. D. Ilyushin and V. A. Blatov

Synopsis: A number of strict rules are proposed to model the crystal structures of intermetallics as a network of cluster precursors. According to these rules the self-assembly of the ZrZn₂₂-like structures was considered within the hierarchical scheme: primary polyhedral clusters (one AX₁₆ + 2BX₁₂) zero-dimensional nanocluster precursor (AB₂X₃₇) one-dimensional primary chain two-dimensional microlayer three-dimensional microframework (three-dimensional supraprecursor).

Online 2 May 2009

 

Acta Cryst. (2009). B65, 308-317  [ doi:10.1107/S0108768109014001 ]

Large, larger, largest - a family of cluster-based tantalum copper aluminides with giant unit cells. I. Structure solution and refinement

T. Weber, J. Dshemuchadse, M. Kobas, M. Conrad, B. Harbrecht and W. Steurer

Synopsis: The structures of a family of three tantalum copper aluminides with giant unit cells have been determined. Their mutual relationships are emphasized by a comparison of their average structures.

Online 19 May 2009

 

Acta Cryst. (2009). B65, 318-325  [ doi:10.1107/S0108768109014013 ]

Large, larger, largest - a family of cluster-based tantalum copper aluminides with giant unit cells. II. The cluster structure

M. Conrad, B. Harbrecht, T. Weber, D. Y. Jung and W. Steurer

Synopsis: The complex cluster structures of a family of three tantalum copper aluminides with giant unit cells are discussed.

Online 19 May 2009

 

Acta Cryst. (2009). B65, 326-333  [ doi:10.1107/S010876810901444X ]

Characterization of the pressure-induced second-order phase transition in the mixed-valence vanadate BaV₆O₁₁

K. Friese, Y. Kanke and A. Grzechnik

Synopsis: The high-pressure behaviour of the mixed-valence vanadate BaV₆O₁₁ was studied with single-crystal X-ray diffraction in a diamond-anvil cell; the pressure-induced transition from P6₃/mmc to P6₃mc was studied in detail.

Online 19 May 2009

    

Acta Cryst. (2009). B65, 334-341  [ doi:10.1107/S0108768109013901 ]

Structures of the pseudo-trigonal polymorphs of Cu₂(OH)₃Cl

T. Malcherek and J. Schlüter

Synopsis: The crystal structure of Cu₂(OH)₃Cl has been refined using two nearly stoichiometric natural specimens. The occurrence of a triclinic polymorph is suggested for pure Cu₂(OH)₃Cl, while clinoatacamite is found for small but significant impurity concentrations.

Online 19 May 2009

 

Acta Cryst. (2009). B65, 342-349  [ doi:10.1107/S0108768109012051 ]

SiBr₄ - prediction and determination of crystal structures

A. K. Wolf, J. Glinnemann, M. U. Schmidt, J. Tong, R. E. Dinnebier, A. Simon and J. Köhler

Synopsis: For SiBr₄ crystal structures were predicted by global lattice-energy minimizations. Two predicted structures could be verified experimentally.

Online 19 May 2009

 

Acta Cryst. (2009). B65, 350-354  [ doi:10.1107/S0108768109013688 ]

Racemic calcium tartrate tetrahydrate [form (II)] in rat urinary stones

A. Le Bail, D. Bazin, M. Daudon, A. Brochot, V. Robbez-Masson and V. Maisonneuve

Synopsis: The structure of racemic [Ca(C₄H₄O₆)]·4H₂O [form (II)] is clarified from powder and single-crystal X-ray diffraction data.

Online 19 May 2009

 

Acta Cryst. (2009). B65, 355-362  [ doi:10.1107/S0108768109006120 ]

Absolute structure determination as a reference for the enantiomeric resolution of racemic mixtures of cyclophosphazenes via chiral high-performance liquid chromatography

S. Coles, D. Davies, M. Hursthouse, S. Yesilot, B. Çosut and A. Kiliç

Synopsis: The absolute configurations of pairs of enantiomers separated by high-performance liquid chromatography have been confirmed by single-crystal structure analysis and provide a reference system for subsequent assignment of such systems based on elution order. The solid-state structures of the pairs of enantiomers do not fully adhere to expected enantiomorphous crystallization behaviour.

Online 2 May 2009

 

Acta Cryst. (2009). B65, 363-374  [ doi:10.1107/S0108768109008271 ]

Charge density and electrostatic potential analyses in paracetamol

N. Bouhmaida, F. Bonhomme, B. Guillot, C. Jelsch and N. E. Ghermani

Synopsis: The charge density of the monoclinic paracetamol drug has been derived from high-resolution X-ray diffraction. Topological features of the electron density and electrostatic potential are presented.

Online 2 May 2009

 

Acta Cryst. (2009). B65, 375-381  [ doi:10.1107/S0108768109004832 ]

Hantzsch 1,4-dihydropyridine esters and analogs: candidates for generating reproducible one-dimensional packing motifs

R. S. Rathore, B. P. Reddy, V. Vijayakumar, R. V. Ragavan and T. Narasimhamurthy

Synopsis: Hantzsch 1,4-dihydropyridine ester analogs, including the prototypical hypertension drug Nifedipine, are of pharmaceutical use but are also good candidates for generating a reproducible packing motif that is characterized by intermolecular N-HO hydrogen-bonded C(6) extended chains.

Online 2 May 2009

 

Acta Cryst. (2009). B65, 382-392  [ doi:10.1107/S0108768109015857 ]

Single-crystal diffuse scattering studies on polymorphs of molecular crystals. I. The room-temperature polymorphs of the drug benzocaine

E. J. Chan, T. R. Welberry, D. J. Goossens, A. P. Heerdegen, A. G. Beasley and P. J. Chupas

Synopsis: Simple Monte Carlo models have been developed that reproduce in detail the diffuse diffraction patterns observed for the two room-temperature polymorphs of the drug benzocaine. The analyses reveal highly correlated molecular displacements in both forms, but in polymorph (II) the motions show non-harmonic characteristics that appear to be precursors of a phase transition to a new polymorph which has been found at low temperatures (150 K).

Online 19 May 2009

 

Acta Cryst. (2009). B65, 393-400  [ doi:10.1107/S0108768109014700 ]

A solution to the observed Z' = 2 preference in the crystal structures of hydrophobic amino acids

C. H. Görbitz, K. Vestli and R. Orlando

Synopsis: Periodic two-dimensional slabs and full three-dimensional networks were extracted from the X-ray structures of hydrophobic amino acids and then optimized with ab initio methods. The derived interaction energies support the observed propensity for inclusion of two molecules in the asymmetric unit.

Online 19 May 2009

 

Acta Cryst. (2009). B65, 401-402  [ doi:10.1107/S0108768109008581 ]

On the correlations between the polyhedron eccentricity parameters and the bond-valence sums for the cations with one lone electron pair. Addendum

V. Sidey

Synopsis: Systematic variations of the bond-valence sums calculated from the poorly determined bond-valence parameters have been illustrated using a simple graphical scheme.

Online 2 May 2009

 

Acta Cryst. (2009). B65, 403  [ doi:10.1107/S0108768109012208 ]

Structural Crystallography of Inorganic Oxysalts

Online 19 May 2009