Acta Crystallographica Section B

Structural Science

Volume 68, Part 2 (April 2012)



[Issue Author Index][Volume Author Index]
[Cover illustration] Cover illustration: A high-angle annular darkfield scanning transmission electron microscopy image of the decagonal quasicrystal Al72Co8Ni20 overlaid with a structure model. Clusters of type 1 (occupied center) highlight transition metal sites (white spheres) and clusters of type 2 (empty center) possess both transition metal and mixed aluminum/transition metal (red) sites. Decagonal-shaped clusters are outlined and exhibit two types of overlap as a unifying building feature of aperiodic quasicrystals of decagonal Al-Co-Ni, Al-Co-Cu and Al-Fe-Ni [Deloudi et al. (2011). Acta Cryst. B67, 1-17, based on Abe & Tsai (2004) J. Non-Cryst. Solids, 334, 198-201]. The 2011 Nobel prize in chemistry was awarded to D. Shechtman for his discovery of quasicrystals.

research papers


thumbnail of article figure

[HTML version][PDF version][CIF][3d view][Structure Factors][Supplementary Material]  [Buy article online]

Acta Cryst. (2012). B68, 101-106  [ doi:10.1107/S0108768111054863 ]

Incommensurate modulation of calcium barium niobate (CBN28 and Ce:CBN28)

H. A. Graetsch, C. S. Pandey, J. Schreuer, M. Burianek and M. Mühlberg

Synopsis: The occupancy of the largest cation site in incompletely filled tetragonal tungsten bronze type CBN28 (calcium barium niobate) is modulated. The occupational modulation is coupled with a modulation of the atomic displacement parameters. The surrounding O atoms are displacively modulated so that the corner-sharing NbO6 octahedra are tilted.

Online 25 February 2012


thumbnail of article figure

[HTML version][PDF version]  [Buy article online]

Acta Cryst. (2012). B68, 107-117  [ doi:10.1107/S0108768112005125 ]

On the structural relations of malachite. I. The rosasite and ludwigite structure families

F. Girgsdies and M. Behrens

Synopsis: The crystal structures of malachite and rosasite are shown to have a common hypothetical aristotype, which is in turn closely related to the ludwigite structure.

Online 20 March 2012


thumbnail of article figure

[HTML version][PDF version]  [Buy article online]

Acta Cryst. (2012). B68, 118-122  [ doi:10.1107/S0108768112002649 ]

On the structural integrity of the spinel block in the [beta]"-alumina structure

D. P. Birnie

Synopsis: Analysis of 40 compounds with the [beta]''-alumina structure type has shown that the thickness of the conduction layers for cationic electrical conduction can be accurately estimated on the basis of the unit-cell dimensions.

Online 25 February 2012


thumbnail of article figure

[HTML version][PDF version][CIF][3d view][Powder data files][Supplementary Material]  [Buy article online]

Acta Cryst. (2012). B68, 123-127  [ doi:10.1107/S0108768112006234 ]

Site occupancy and lattice parameters in sigma-phase Co-Cr alloys

J. Cieslak, S. M. Dubiel and M. Reissner

Synopsis: The neutron diffraction technique was used to determine site occupancies and the unit-cell parameters in sigma-phase Co-Cr alloys. The latter show a linear dependence on temperature, T, with a change of the slope at T [asymptotically equal to] 100 K.

Online 20 March 2012


thumbnail of article figure

[HTML version][PDF version][CIF][3d view][Structure Factors]  [Buy article online]

Acta Cryst. (2012). B68, 128-136  [ doi:10.1107/S0108768112005782 ]

Structures and phase transitions in a new ferroelectric - pyridinium chlorochromate - studied by X-ray diffraction, DSC and dielectric methods

H. Maluszynska, P. Czarnecki, A. Czarnecka and Z. Pajak

Synopsis: The crystal structures of four phases of a new ferroelectric - pyridinium chlorochromate - are determined by single-crystal X-ray diffraction. Structural, calorimetric and dielectric studies allow for the description and classification of the three phases transitions.

Online 20 March 2012


thumbnail of article figure

[HTML version][PDF version][CIF][3d view][Structure Factors]  [Buy article online]

Acta Cryst. (2012). B68, 137-149  [ doi:10.1107/S0108768112009263 ]

Rationalizing the molecular origins of Ru- and Fe-based dyes for dye-sensitized solar cells

K. S. Low, J. M. Cole, X. Zhou and N. Yufa

Synopsis: Structure-property relationships are established in a series of Ru- and Fe-based metal-organic dyes that rationalize their optoelectronic performance in dye-sensitized solar cells.

Online 20 March 2012


thumbnail of article figure

[HTML version][PDF version][CIF][3d view][Structure Factors][Supplementary Material]  [Buy article online]

Acta Cryst. (2012). B68, 150-157  [ doi:10.1107/S0108768112002728 ]

Detailed example of the identification and crystallographic analysis of a pseudo-merohedrally twinned crystal

I. Guzei, R. Herbst-Irmer, A. Munyaneza and J. Darkwa

Synopsis: A detailed description of the crystal structure solution and refinement of a pseudo-merohedrally twinned crystal of an organometallic complex is presented as a guide to the handling of similar non-routine challenging crystal structures. The interpretation of the signs of twinning and the logic behind the selection of the correct space group are explained. In this case the crystal twinning was complicated by pseudo-symmetry of the ionic species and positional disorder of several atoms.

Online 20 March 2012


thumbnail of article figure

[HTML version][PDF version][CIF][3d view][Structure Factors]  [Buy article online]

Acta Cryst. (2012). B68, 158-163  [ doi:10.1107/S0108768112007999 ]

Two novel Zn-MOFs: structures and characterization

R. Zheng, L. Han, Q. Pan, K. E. Christensen and T. Ren

Synopsis: Two Zn metal organic frameworks (Zn-MOFs) have been synthesized with a controlled pH environment in the hydrothermal synthesis. Two novel coordination modes between Zn metal and carboxylate were observed in the structures presented. These two compounds show photoluminescence and thermal stability above 673 K.

Online 20 March 2012


thumbnail of article figure

[HTML version][PDF version][CIF][3d view][Structure Factors][Powder data file]  [Buy article online]

Acta Cryst. (2012). B68, 164-170  [ doi:10.1107/S0108768112004284 ]

Structure of the inclusion complex of [beta]-cyclodextrin with lipoic acid from laboratory powder diffraction data

C.-P. Rácz, G. Borodi, M. M. Pop, I. Kacso, S. Sánta and M. Tomoaia-Cotisel

Synopsis: The crystal structure of the inclusion complex of [beta]-cyclodextrin with lipoic acid was determined from laboratory powder diffraction data.

Online 25 February 2012


thumbnail of article figure

[HTML version][PDF version][CIF][3d view]  [Buy article online]

Acta Cryst. (2012). B68, 171-181  [ doi:10.1107/S0108768112003138 ]

Ab-initio crystal structure analysis and refinement approaches of oligo p-benzamides based on electron diffraction data

T. E. Gorelik, J. van de Streek, A. F. M. Kilbinger, G. Brunklaus and U. Kolb

Synopsis: The crystal structure of the oligo p-benzamide containing four benzamide units (OPBA4) was solved ab initio from electron diffraction data. The structure solution and refinement strategy was validated on the known structure of OPBA3 and then applied to OPBA4.

Online 25 February 2012


thumbnail of article figure

[HTML version][PDF version]  [Buy article online]

Acta Cryst. (2012). B68, 182-188  [ doi:10.1107/S0108768111054991 ]

Geometry and conformation of cyclopropane derivatives having [sigma]-acceptor and [sigma]-donor substituents: a theoretical and crystal structure database study

A. J. Cruz-Cabeza and F. H. Allen

Synopsis: Bond-length asymmetry in cyclopropane rings carrying [sigma]-acceptor or [sigma]-donor substituents has been studied using density-functional theory calculations and analysis of crystal structures in the Cambridge Structural Database. Both methods are in excellent agreement and show that [sigma]-accepting halogen substituents induce positive asymmetry, but that this effect is reversed for [sigma]-donors such as SiH3 or Si(CH3)3.

Online 25 February 2012


thumbnail of article figure

[HTML version][PDF version][CIF][3d view][Structure Factors][Supplementary Material]  [Buy article online]

Acta Cryst. (2012). B68, 189-203  [ doi:10.1107/S0108768112006799 ]

Structural systematics and conformational analyses of a 3 × 3 isomer grid of fluoro-N-(pyridyl)benzamides: physicochemical correlations, polymorphism and isomorphous relationships

P. Mocilac, K. Donnelly and J. F. Gallagher

Synopsis: A 3 × 3 isomer grid of fluoro-N-(pyridyl)benzamides including two polymorphs has been examined to correlate structural relationships between the solid state and ab initio geometry optimizations. Melting point data demonstrate the importance of the substituent position rather than the nature of the substituent.

Online 20 March 2012


thumbnail of article figure

[HTML version][PDF version][CIF][3d view][Structure Factors]  [Buy article online]

Acta Cryst. (2012). B68, 204-208  [ doi:10.1107/S0108768112008592 ]

Form, function and functionality of two dimeric toluene-2,4-diisocyanate polymorphs

L. Vella-Zarb and R. E. Dinnebier

Synopsis: The crystal structures of two polymorphs of dimeric toluene-2,4-diisocyanate have been solved from high-resolution laboratory X-ray powder diffraction data. A study of their intermolecular energies highlighted the differences in physical properties observed between the two forms.

Online 20 March 2012


short communications


thumbnail of article figure

[HTML version][PDF version]  [Buy article online]

Acta Cryst. (2012). B68, 209-212  [ doi:10.1107/S0108768112008294 ]

Symmetry analysis of the structural and magnetic phase transitions in 122 iron arsenides

C. J. Howard and M. A. Carpenter

Synopsis: The magnetic space-group symmetry of the low-temperature antiferromagnetic structure of the 122 iron arsenide (XFe2As2) has been identified, and group theory used to analyse the transition(s) between this phase and the room-temperature paramagnetic structure.

Online 20 March 2012


obituaries


thumbnail of article figure

[HTML version][PDF version]  [Open access]

Acta Cryst. (2012). B68, 213-214  [ doi:10.1107/S0108768112003540 ]

Sagrario Martínez-Carrera (1925-2011)

M. Martínez-Ripoll

Synopsis: Obituary for Sagrario Martínez-Carrera

Online 20 March 2012


Copyright © International Union of Crystallography
IUCr Webmaster