Acta Crystallographica Section B

Structural Science

Volume 54, Part 3 (June 1998)

Cover illustration: Space filling representation of the hydrated anionic framework formed by trimesic acid around piles of cobalticinium cations in crystalline [(C₅H₅)₂Co][(H₃TMA)(H₂TMA)].2H₂O. Graphics (picture or drawing) obtained using SCHAKAL by E. Keller, University of Freiburg, Germany. Courtesy of D. Braga and F. Grepioni

research papers

research papers

Acta Cryst. (1998). B54, 197-203 [doi:10.1107/S0108768197012032]

Structural Analysis of Cs₂HgBr₄ in Normal, Incommensurate and Twinned Phases

C. B. Pinheiro, A. Jório, M. A. Pimenta and N. L. Speziali

Synopsis: X-ray diffraction and Raman spectroscopy have shown that the crystal structure of Cs₂HgBr₄ in the normal, incommensurate and low-temperature phases can be described by disordered models.

Acta Cryst. (1998). B54, 204-210 [doi:10.1107/S0108768197012809]

Theoretical Prediction of Bond-Valence Networks. II. Comparison of the Graph-Matrix and Resonance-Bond Approaches

J. S. Rutherford

Synopsis: The bond-valence and resonance-bond-number methods for calculating interatomic distances are compared for KVO₃, [beta] -Ga₂O₃, TeI₄, Li₂SiO₃, Li₂GeO₃ and CaCrF₅.

Acta Cryst. (1998). B54, 211-220 [doi:10.1107/S0108768197013177]

Monoclinic and Hexagonal Nepheline Structures of (Na_3/4/K_1/4)AlGeO₄

R. P. Hammond and J. Barbier

Synopsis: Hexagonal (Na_3/4K_1/4)AlGeO₄ is isostructural with the mineral nepheline, (Na_3/4K_1/4)AlSiO₄, with a similar split oxygen position and a cation deficiency on the potassium site. In contrast, the alkali sites are fully occupied in the structure of monoclinic (Na_3/4K_1/4)AlGeO₄ and the lower unit-cell symmetry eliminates the oxygen disorder.

Acta Cryst. (1998). B54, 221-230 [doi:10.1107/S0108768197013426]

Determination of the Bonding and Valence Distribution in Inorganic Solids by the Maximum Entropy Method

G. H. Rao and I. D. Brown

Synopsis: The maximum entropy method provides a means of ranking bond graphs in order of symmetry and gives good predictions of the bond valences.

Acta Cryst. (1998). B54, 231-239 [doi:10.1107/S0108768197014146]

Comparison of Experimental and Theoretical Structure Amplitudes and Valence Charge Densities of GaAs

J. Stahn, M. Möhle and U. Pietsch

Synopsis: The valence and difference charge densities of GaAs obtained from experimental and theoretical data (Hartree-Fock and density functional theory) show a charge accumulation between nearest neighbours slightly shifted towards the arsenic site. The disagreement remaining between experimental and theoretical data and between those of both ab initio methods are of the same order of magnitude.

Acta Cryst. (1998). B54, 240-249 [doi:10.1107/S010876819701971X]

Order and Disorder in Niobium Tungsten Oxides of the Tetragonal Tungsten Bronze Type

F. Krumeich

Synopsis: Distinct types of diffuse scattering which appear in the electron diffraction patterns of tetragonal tungsten bronze-type (TTB) niobium tungsten oxides are caused by different arrangements of filled pentagonal tunnels. A structural model for a new TTB superstructure (Nb₆W₈O₃₉) has been derived from HRTEM images.

Acta Cryst. (1998). B54, 250-256 [doi:10.1107/S0108768197008951]

Classification and Distortion in Six-Coordinate Bis(salicylaldiminato)nickel(II) Complexes: Crystal Structure of Bis[2-[[(2-hydroxyphenyl)methylene]amino]-1-phenyl-1,3-propanediolato]nickel(II).2H₂O

M. L. Glówka, A. Olczak, J. Karolak-Wojciechowska and E. Ciechanowska-Urbanska

Synopsis: A new classification based on the geometry of the coordination polyhedron, especially useful for six-coordinate bis(salicyl- aldiminato) complexes, has been proposed. The distortions of octahedral Ni²⁺ complexes have been analyzed and exemplified by a crystal structure of a complex showing the largest shift of the metal from the geometric center observed so far in similar complexes.

Acta Cryst. (1998). B54, 257-263 [doi:10.1107/S0108768197011543]

X-ray Studies on Crystalline Complexes Involving Amino Acids and Peptides. XXXIII. Crystal Structures of L- and DL-Arginine Complexed with Oxalic Acid and a Comparative Study of Amino Acid-Oxalic Acid Complexes

N. R. Chandra, M. M. Prabu, J. Venkatraman, S. Suresh and M. Vijayan

Synopsis: The oxalic acid complexes of DL and L forms of basic amino acids exhibit a variety of ionization states and stoichiometries. They demonstrate the tendency of individual molecules to retain their intrinsic aggregation propensities even as they interact with other molecules.

Acta Cryst. (1998). B54, 264-276 [doi:10.1107/S0108768197012020]

Pseudoacids. II. 2-Acylbenzoic Acid Derivatives

E. J. Valente, S. B. Martin and L. D. Sullivan

Synopsis: Structures of the cyclic derivatives of o-acylbenzoic acids, including the chloride, endo- and exocyclic amides, the ester and two types anhydride, are described. Former aldehyde/ketone carbon-heteroatom endocyclic and exocyclic bond distances show length variations which correlate with the relative basicities of the attached groups.

Acta Cryst. (1998). B54, 277-290 [doi:10.1107/S0108768197012135]

Structural, Thermodynamic and Kinetic (Hysteresis) Aspects of the Enantiotropic First-Order Phase Transformations of N-Anilinophthalimide and N-(N'-Methylanilino)phthalimide

M. Botoshansky, A. Ellern, N. Gasper, J.-O. Henck and F. H. Herbstein

Synopsis: Physico-chemical studies of the phase transformations by Chattaway and co-workers (1911-1915) are extended by structure determinations for the four phases involved and DSC measurements on the transformations.

Acta Cryst. (1998). B54, 291-299 [doi:10.1107/S0108768197013384]

Hypothetical Crystal Structures of Benzene at 0 and 30 kbar

B. P. van Eijck, A. L. Spek, W. T. M. Mooij and J. Kroon

Synopsis: An attempt has been made to unify and extend previous predictions of the possible crystal packings of benzene. Dozens of hypothetical structures were generated, but the two experimentally observed ones still have the lowest enthalpy at their respective pressures.

Acta Cryst. (1998). B54, 300-307 [doi:10.1107/S0108768197013402]

Structure of Z-(Aib)₉OBu^t

R. Geßmann, H. Brückner and M. Kokkinidis

Synopsis: Z-(Aib)₉OBu^t contains the unusual [alpha] -aminoisobutyric acid. The structure of this synthetic oligopeptide reveals a rare C-terminal conformation in the form of a disorder of one of the two molecules in the asymmetric unit.

Acta Cryst. (1998). B54, 308-315 [doi:10.1107/S0108768197013414]

Temperature Dependence of the Rigid-Body Motion of Anthraquinone

Y. Fu and C. P. Brock

Synopsis: The precision of previous studies may have been limited by twinning. Analyses of data collected at five temperatures show that the temperature dependence of the rigid-body motion is normal and confirm that the out-of-plane motion of the O atoms is large.

Acta Cryst. (1998). B54, 316-319 [doi:10.1107/S0108768197014602]

Hydrogen Bonding to Thiocyanate Anions: Statistical and Quantum-Chemical Analyses

J. P. M. Lommerse and J. C. Cole

Synopsis: A re-investigation of the formation of hydrogen bonds to the thiocyanate anion demonstrates that preferred hydrogen-bond geometries are in the directions of the sulfur and nitrogen lone pairs of the anion.

Acta Cryst. (1998). B54, 320-329 [doi:10.1107/S0108768198001463]

Carbonyl-Carbonyl Interactions can be Competitive with Hydrogen Bonds

F. H. Allen, C. A. Baalham, J. P. M. Lommerse and P. R. Raithby

Synopsis: Three C=OC=O interaction motifs are commonly observed in crystal structures: the antiparallel, perpendicular and sheared-parallel motifs. Ab-initio molecular-orbital calculations on a bis-propanone dimer model yield interaction energies of -22 kJ mol^-1 for the antiparallel motif, having two short CO interactions, and -7.6 kJ mol^-1 for the perpendicular motif, having only one such short dipolar interaction.

Acta Cryst. (1998). B54, 330-338 [doi:10.1107/S010876819701495X]

Crystal Engineering Using Tris-phenols. Cross-Linked, Pairwise-Interwoven Two-Dimensional Nets in the 2:1 Adduct of 1,1,1-Tris(4-hydroxyphenyl)ethane with 1,2-Diaminoethane

G. Ferguson, C. Glidewell, R. M. Gregson and P. R. Meehan

Synopsis: Pairwise-interwoven nets built from tris-phenol molecules are cross-linked into two-dimensional bilayers by 1,2-diamino- ethane molecules.

Acta Cryst. (1998). B54, 339-344 [doi:10.1107/S0108768197015218]

Uric Acid Dihydrate Revisited

S. Parkin and H. Hope

Synopsis: Refinement of uric acid dihydrate as both twinned and disordered in space group P2₁/c fully accounts for inconsistencies present in previous orthorhombic descriptions.

Acta Cryst. (1998). B54, 345-350 [doi:10.1107/S0108768198000093]

Structural Determination of the Hydrofullerene C₆₀D₃₆ by Neutron Diffraction

L. E. Hall, D. R. McKenzie, R. L. Davis, M. I. Attalla and A. M. Vassallo

Synopsis: Five proposed structures are compared with the reduced density function derived from neutron diffraction data. A T symmetry structure provides the best agreement.