Acta Crystallographica Section B

Structural Science

Volume 67, Part 4 (August 2011)

Cover illustration: The cover picture highlights an artefact in the electrostatic potential of the macrolide antibiotic roxithromycin as derived via multipole refinement of X-ray diffraction data.  Ignoring the hydrogen disorder (left) in the oxime chain leads to a falsely positive electrostatic potential there as a result of the multipole model's being flexible enough to fit the averaged electron density.  If the invariom formalism, which uses theoretical electron density, is applied to the disordered region (right) the artefact disappears.  A procedure for obtaining reliable electron density distributions in the presence of disorder has been proposed [Holstein et al. (2010). Acta Cryst. B66, 568-577].

• feature articles
• research papers
• addenda and errata

feature articles

Acta Cryst. (2011). B67, 269-292  [ doi:10.1107/S0108768111025390 ] Structural building principles of complex face-centered cubic intermetallics J. Dshemuchadse, D. Y. Jung and W. Steurer Synopsis: Common fundamental structural building principles are discussed for complex intermetallics with giant unit cells and symmetries , , , and . Online 18 July 2011

research papers

Acta Cryst. (2011). B67, 293-301  [ doi:10.1107/S0108768111018544 ] CaSeO4·0.625H2O - water channel occupation in a bassanite related structure S. Fritz, H. Schmidt, I. Paschke, O. V. Magdysyuk, R. E. Dinnebier, D. Freyer and W. Voigt Synopsis: CaSeO4·0.625H2O was synthesized under hydrothermal conditions. The crystal structure was solved by single-crystal diffraction, and thermal and vibrational properties were analysed. Online 18 July 2011

Acta Cryst. (2011). B67, 302-314  [ doi:10.1107/S0108768111018313 ] Octahedral tilts, symmetry-adapted displacive modes and polyhedral volume ratios in perovskite structures D. Wang and R. J. Angel Synopsis: Polyhedral volume ratios in 15 tilted perovskite structures are expressed in terms of symmetry-adapted mode amplitudes and tilt angles around three pseudo-cubic axes. Online 18 July 2011

Acta Cryst. (2011). B67, 315-323  [ doi:10.1107/S0108768111022695 ] Bis(2-2-(dimethylamino)ethoxo-N,O,O)-di(phenolyato-O)ditin(II): a high-resolution single-crystal X-ray diffraction and quantum chemical study A. A. Korlyukov, V. N. Khrustalev, A. V. Vologzhanina, K. A. Lyssenko, M. S. Nechaev and M. Y. Antipin Synopsis: Peculiarities of the electronic structure of bis(µ2-2-(dimethylamino)ethoxo-N,O,O)-di(phenolyato-O)ditin(II) and, particularly, of the electron lone pair of tin have been investigated in the gas phase and the solid state with Bader's `Atoms in Molecules' theory. Online 18 July 2011

Acta Cryst. (2011). B67, 324-332  [ doi:10.1107/S0108768111022671 ] d-Orbital orientation in a dimer cobalt complex: link to magnetic properties? M. Deutsch, N. Claiser, J.-M. Gillet, C. Lecomte, H. Sakiyama, K. Tone and M. Souhassou Synopsis: The experimental charge density was studied to explore the electronic origin of the unexpected magnetic behaviour of a cobalt molecular complex. Online 18 July 2011

Acta Cryst. (2011). B67, 333-349  [ doi:10.1107/S0108768111024608 ] Deducing chemical structure from crystallographically determined atomic coordinates I. J. Bruno, G. P. Shields and R. Taylor Synopsis: An improved algorithm has been written for assigning chemical structures to incoming entries to the Cambridge Structural Database. Online 18 July 2011

Acta Cryst. (2011). B67, 350-356  [ doi:10.1107/S0108768111017575 ] Conformational preference of chlorothioformate species: molecular structure of ethyl chlorothioformate, ClC(O)SCH2CH3, in the solid phase and NBO analysis L. Rodríguez Pirani, M. F. Erben, R. Boese, C. G. Pozzi, A. C. Fantoni and C. O. Della Védova Synopsis: The molecular and crystal structure of crystalline ClC(O)SCH2CH3 was obtained by low-temperature X-ray diffraction. A joint analysis of experimental and theoretical data based on AIM theory and NBO population analysis was performed. Online 9 June 2011

Acta Cryst. (2011). B67, 357-364  [ doi:10.1107/S0108768111021653 ] Determination of the crystal structure of nifedipine form C by synchrotron powder diffraction M. Bortolotti, I. Lonardelli and G. Pepponi Synopsis: The crystal structure of the metastable polymorph C of nifedipine [3,5-dimethyl 2,6-dimethyl-4-(2-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylate] was determined by means of ab initio direct-space methods applied to synchrotron powder diffraction data. Additionally, the crystallization kinetics and thermal stability of the nifedipine system were examined in-situ. Online 18 July 2011

Acta Cryst. (2011). B67, 365-378  [ doi:10.1107/S0108768111022683 ] R-free factor and experimental charge-density analysis of 1-(2'-aminophenyl)-2-methyl-4-nitroimidazole: a crystal structure with Z' = 2 A. Paul, M. Kubicki, C. Jelsch, P. Durand and C. Lecomte Synopsis: Free R-factor calculations were used to define the optimal weights on symmetry and similarity restraints in the experimental charge-density analysis of a small organic compound with two molecules in the asymmetric unit. An anharmonic model was applied to the N atoms of the amino groups and to one nitro group in order to account for the high residual density peaks in harmonic refinement and to obtain a better charge-density model. Online 18 July 2011

addenda and errata