Acta Crystallographica Section B

Structural Science

Volume 52, Part 6 (December 1996)

Cover illustration: Structural model of ZrnNb8-2nW12+nO56. Courtesy of F. Krumeich, G. Liedtke and W. Mader.

• research papers
• short communications
• book reviews
• books received
• international union of crystallography

research papers

Acta Cryst. (1996). B52, 899-904    [doi:10.1107/S0108768196002996]

Villamaninite, a case of noncubic pyrite-type structure

C. Marcos, A. Paniagua, D. B. Moreiras, S. García-Granda and M. R. Díaz

Synopsis: A single-crystal X-ray study was carried out on two villamaninite samples from Villamanín (León, Spain). The systematic structural refinement over subgroups of the pyrite Pa-3 space group leads to a monoclinic model, space group P12₁1, for this mineral.

Acta Cryst. (1996). B52, 905-908    [doi:10.1107/S0108768196003916]

Synthèse et caractérisation structurale d'un phosphate d'indium In₃P₂O₈ présentant des paires In-In

V. Peltier, P. L'Haridon, R. Marchand et Y. Laurent

Synopsis: The crystal structure of the new indium phosphate In₃P₂O₈ is characterized by a three-dimensional arrangement of isolated PO₄^3- tetrahedra forming the anionic network, while the electroneutrality is ensured by (In-In)⁴⁺ cationic pairs.

Acta Cryst. (1996). B52, 909-916    [doi:10.1107/S0108768196005988]

Structures and isomerization in diamminedichloropalladium(II)

S. D. Kirik, L. A. Solovyov, A. I. Blokhin, I. S. Yakimov and M. L. Blokhina

Synopsis: Three forms (cis-, trans-and -trans-) of [Pd(NH₃)₂Cl₂] were investigated by X-ray powder diffraction. The crystal structures obtained form the basis for considering the possible mechanisms of isomerization.

Acta Cryst. (1996). B52, 917-922    [doi:10.1107/S0108768196006891]

A novel intergrowth structure between ReO₃-type and tetragonal tungsten bronze-type in the Zr/Nb/W/O system

F. Krumeich, G. Liedtke and W. Mader

Synopsis: Electron diffraction and high-resolution transmission electron microscopy investigations reveal the structure of Zr_nNb_8-2nW_12+nO₅₆ (0.5<n<1). The characteristic structural features are double pentagons composed of edge-sharing five-membered rings of octahedra.

Acta Cryst. (1996). B52, 923-931    [doi:10.1107/S010876819600794X]

Atomic displacement parameters for Ni(ND₃)₄(NO₂)₂ from 9 K X-ray and 13 K time-of-flight neutron diffraction data

B. B. Iversen, F. K. Larsen, B. N. Figgis, P. A. Reynolds and A. J. Schultz

Synopsis: Excellent agreement is obtained between both positional and thermal parameters derived separately from very low-temperature X-ray and time-of-flight neutron diffraction data. This gives confidence in the deconvolution of thermal motion from the X-ray data in a subsequent calculation of the static electron density distribution.

Acta Cryst. (1996). B52, 932-938    [doi:10.1107/S0108768196008075]

Synthesis and structure refinement of a new type of layered intergrowth phase: Sb_3+xNb_3-xTiO₁₄ and Sb_3+xTa_3-xTiO₁₄

C. D. Ling, S. Schmid, J. G. Thompson, R. L. Withers and M. Sterns

Synopsis: The isomorphous phases Sb_3+xNb_3-xTiO₁₄ and Sb_3+xTa_3-x-TiO₁₄ have been discovered and their structures solved. They have layered structures related to those found in simpler oxides of Sb^III and Sb^V.

Acta Cryst. (1996). B52, 939-953    [doi:10.1107/S0108768196009202]

An extension of the Voronoi analysis of crystal structures

N. W. Thomas

Synopsis: A new methodology is defined for discriminating between different crystal structures on the basis of their Voronoi polyhedra.

Acta Cryst. (1996). B52, 954-960    [doi:10.1107/S0108768196009214]

A re-examination of the relationship between lattice strain, octahedral tilt angle and octahedral strain in rhombohedral perovskites

N. W. Thomas

Synopsis: The relationship between lattice strain and BO₆ octahedral tilt angle is examined in rhombohedral perovskites, ABO₃. Consideration is also given to factors governing the observed space group.

Acta Cryst. (1996). B52, 961-965    [doi:10.1107/S0108768196009597]

Structure of UMoO₅ studied by single-crystal X-ray diffraction and high-resolution transmission electron microscopy

O. G. D'yachenko, V. V. Tabachenko, R. Tali, L. M. Kovba, B.-O. Marinder and M. Sundberg

Synopsis: A combination of X-ray diffraction and high-resolution transmission electron microscopy has been used to study the crystal structure of UMoO₅, obtained by hydrothermal and ceramic methods. The structure is related to that of UVO₅.

Acta Cryst. (1996). B52, 966-975    [doi:10.1107/S0108768196009639]

Structural relationship of various squarates

C.-R. Lee, C.-C. Wang and Y. Wang

Synopsis: The structural relationship between three types of metal squarates and the ligand squarate in its acid form and in its monoanion form is illustrated. It relies heavily on intra-and intermolecular hydrogen bonds.

Acta Cryst. (1996). B52, 976-981    [doi:10.1107/S0108768196005502]

Temperature dependence of crystal structure of NaK_0.72(NH₄)_0.28(+)-C₄H₄O₆.4H₂O in the paraelectric phase

E. Suzuki, H. Kabasawa, T. Honma, R. Nozaki and Y. Shiozaki

Synopsis: X-ray investigations reveal details of structural change with temperature in the paraelectric phase of Rochelle salt-ammonium Rochelle salt mixed crystal.

Acta Cryst. (1996). B52, 982-988    [doi:10.1107/S0108768196006829]

Ab initio powder structure determination and thermal behavior of a new lead(II) phenylphosphonate, Pb(O₃PC₆H₅)

A. Cabeza, M. A. G. Aranda, M. Martinez-Lara, S. Bruque and J. Sanz

Synopsis: The structure of layered Pb(O₃PC₆H₅) has been determined ab initio from powder diffraction data by minimizing the preferred orientation. MAS-NMR has been used to confirm the triclinic structure with two independent structural units.

Acta Cryst. (1996). B52, 989-998    [doi:10.1107/S010876819600451X]

Inclusion compounds of thiourea and peralkylated ammonium salts. III. Hydrogen-bonded host lattices built of thiourea and nitrate ions

Q. Li and T. C. W. Mak

Synopsis: The present series of thiourea-quaternary ammonium nitrate complexes exhibit two distinctly different types of thiourea-anion lattices depending on the stoichiometric ratio of thiourea to nitrate ion. Compouds (1) and (2) (3:1) are novel channel inclusion compounds, whereas (3), (4) and (5) (1:1) are each characterized by an anionic composite ribbon composed of a zigzag arrangement of thiourea molecules with nitrate ions attached to both sides.

Acta Cryst. (1996). B52, 999-1006    [doi:10.1107/S0108768196006817]

Structures of L-valyl-L-glutamine and L-glutamyl-L-valine

C. H. Görbitz and P. H. Backe

Synopsis: The title compounds were compared with other mixed hydrophobic-hydrophilic dipeptides. Emphasis is placed on crystal packing patterns and hydrogen-bond preferences.

Acta Cryst. (1996). B52, 1007-1013    [doi:10.1107/S0108768196009056]

Structures and photochemistry of dibenzobarrelene monoamides

R. Jones, A. G. M. Rattray, S. J. Rettig, J. R. Scheffer and J. Trotter

Synopsis: The photochemistry of 9,10-ethenoanthracene-11-monoamides has been studied and correlated with the crystal structures determined for two derivatives; photoproduct structures have been established from a crystal structure analysis of one of the products and from NMR correlations. Mechanisms are derived for the formation of three types of photoproduct: (i) the well known di-i-methane reaction [(2M)-type photoproduct]; (ii) a hydrogen abstraction process [(2H)]; (iii) -lactam formation [(2L)].

Acta Cryst. (1996). B52, 1014-1022    [doi:10.1107/S0108768196008300]

Methyl group conformation-determining intermolecular C-HO hydrogen bonds: structure of N-methyl-2-pyrrolidone

G. Müller, M. Lutz and S. Harder

Synopsis: In crystalline N-methyl-2-pyrrolidone (NMP) the N-methyl group takes part in two intermolecular C-HO hydrogen bonds, which cause a notable deviation from its usually preferred conformation with one C-H bond being almost eclipsed to the adjacent N-C amide bond. This is substantiated by force-field and ab initio calculations on isolated NMP molecules.

Acta Cryst. (1996). B52, 1023-1035    [doi:10.1107/S0108768196008294]

Molecular electric moments and electric field gradients from X-ray diffraction data: model studies

M. A. Spackman and P. G. Byrom

Synopsis: Model X-ray data sets are computed from ab initio molecular electron densities for 12 different molecular crystals. By the use of several multipole models, molecular dipole and second moments, as well as electric field gradients at each nuclear site, are computed and compared with those from the original ab initio wavefunctions. The results provide valuable insight into the reliability of these properties extracted in the same way from experimental X-ray data.

Acta Cryst. (1996). B52, 1036-1047    [doi:10.1107/S0108768196009937]

Hexamethylenetetramine suberate, a strongly anharmonic modulated structure

V. Bussien Gaillard, W. Paciorek, K. Schenk and G. Chapuis

Synopsis: The incommensurate structure of hexamethylenetetramine suberate is characterized by large non-sinusoidal displacements of up to 1 Å. The modulation results from the constrained packing of the aliphatic chains with layers of hexamine.

Acta Cryst. (1996). B52, 1048-1056    [doi:10.1107/S0108768196005216]

Symmetry constraints, molecular recognition and crystal engineering. Comparative structural studies of urea-butanedioic and urea-E-butanedioic acid (2:1) cocrystals

V. Videnova-Adrabinska

Synopsis: The crystal structure of two urea-,-dicarboxylic acid cocrystals (2:1) are determined. The geometry and the conformation of the comolecular units and their parent molecules are studied with respect to the three-dimensional network organization. The effective molecular recognition in crystals is demonstrated to be not only dynamically selective and functionally complementary, but also a toposelective and symmetry-constrained process.

short communications

Acta Cryst. (1996). B52, 1057    [doi:10.1107/S0108768196099843]

Prediction of ferroelectricity in recent inorganic crystal structure database entries under space group pba2. Erratum

S. C. Abrahams, K. Mirsty and R. M. Nielson

Synopsis: Correction to Acta Cryst. (1996), B52, 806-809.

book reviews

Acta Cryst. (1996). B52, 1058    [doi:10.1107/S0108768196012177]

Molecular modeling of inorganic compounds edited by P. Comba and T. W. Hambley

books received

Acta Cryst. (1996). B52, 1058-1059    [doi:10.1107/S0108768196099831]

Fundamental principles of molecular modeling by W. Gans, A. Amann and J. C. A. Boeyens

international union of crystallography

Acta Cryst. (1996). B52, 1060-1061    [doi:10.1107/S010876819609982X]

Prices of IUCr Journals

Acta Cryst. (1996). B52, 1063-1069

Subject index to volume B52 (1996)

Acta Cryst. (1996). B52, 1070-1071

Formula index to volume B52 (1996)

Acta Cryst. (1996). B52, 1072-1078

Author index to volume B52 (1996)

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