Acta Crystallographica Section B: Structural Science Volume 68, Part 2 (April 2012) Copyright (c) International Union of Crystallography 2012 ----------------------------------------------------------------- [Issue Author Index][Volume Author Index] * research papers * short communications * obituaries ----------------------------------------------------------------- research papers ----------------------------------------------------------------- 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. Muehlberg 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 NbO[6] octahedra are tilted. Online 25 February 2012 ----------------------------------------------------------------- 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 ----------------------------------------------------------------- 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 ----------------------------------------------------------------- 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 ----------------------------------------------------------------- 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 ----------------------------------------------------------------- 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 ----------------------------------------------------------------- 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 ----------------------------------------------------------------- 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-MOs) 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 ----------------------------------------------------------------- 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. Racz, G. Borodi, M. M. Pop, I. Kacso, S. Santa 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 ----------------------------------------------------------------- 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 ----------------------------------------------------------------- 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 SiH[3] or Si(CH[3])[3]. Online 25 February 2012 ----------------------------------------------------------------- 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 ----------------------------------------------------------------- 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 ----------------------------------------------------------------- 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 (XFe[2]As[2]) 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 ----------------------------------------------------------------- [Open access] Acta Cryst. (2012). B68, 213-214 [ doi:10.1107/S0108768112003540 ] Sagrario Martinez-Carrera (1925-2011) M. Martinez-Ripoll Synopsis: Obituary for Sagrario Martinez-Carrera Online 20 March 2012 -----------------------------------------------------------------