Acta Crystallographica Section B

Structural Science

Volume 66, Part 5 (October 2010)

Cover illustration: The clusters shown on the cover image belong to the fundamental structural building units of cF(5928-x)-Al56.6Cu3.9Ta39.5, x = 20, one representative of a family of cluster-based tantalum copper aluminides with giant unit cells hosting up to more than 20 000 atoms. Their structures can be geometrically described as packings of clusters such as fullerenes, dodecahedra, pentagonal bifrusta, hexagonal bipyramids and Friauf polyhedra [Conrad et  al. (2009). Acta Cryst. B65, 318-325; see also Weber et  al. (2009). Acta Cryst. B65, 308-317].

• research papers

research papers

Acta Cryst. (2010). B66, 493-496  [ doi:10.1107/S0108768110031071 ] Symmetry of platelet defects in diamond: new insights with synchrotron light A. Bosak, D. Chernyshov, M. Krisch and L. Dubrovinsky Synopsis: Diffuse scattering of synchrotron radiation has been applied to characterize platelet defects in diamond. The intensity distribution along diffuse rods has been measured and used for recognition of symmetry elements of the platelet structure. Online 4 September 2010

Acta Cryst. (2010). B66, 497-502  [ doi:10.1107/S0108768110031459 ] Single-crystal neutron diffraction investigation on crystals belonging to the langasite family: a comparative study R. Chitra and R. R. Choudhury Synopsis: Single-crystal neutron diffraction studies were carried out on crystals of the langasite family. The effect of compositional variation on the piezoelectric properties of the crystal was illustrated through structural studies. Online 4 September 2010

Acta Cryst. (2010). B66, 503-514  [ doi:10.1107/S0108768110031496 ] Bond catastrophes in rhodium complexes: experimental charge-density studies of [Rh(C7H8)(PtBu3)Cl] and [Rh(C7H8)(PCy3)Cl] H. A. Sparkes, A. B. Chaplin, A. S. Weller and J. A. K. Howard Synopsis: The title compounds serve as precursors to larger more exotic rhodium compounds containing Rh(C-C) sigma interactions, which are postulated as intermediates in transition-metal-catalysed C-C bond activation. As a result, experimental charge-density studies have been undertaken on the title compounds to obtain unique insights into the bonding and interactions around rhodium, which will provide useful benchmarks when studying larger species containing Rh(C-C) sigma interactions. Online 11 September 2010

Acta Cryst. (2010). B66, 515-526  [ doi:10.1107/S0108768110028247 ] Experimental and predicted crystal structures of Pigment Red 168 and other dihalogenated anthanthrones M. U. Schmidt, E. F. Paulus, N. Rademacher and G. M. Day Synopsis: Why do the four derivatives of this pigment crystallize in four different crystal structures? Answers are given by lattice-energy calculations with anisotropic potentials and with the PIXEL method. Online 11 September 2010

Acta Cryst. (2010). B66, 527-543  [ doi:10.1107/S0108768110029514 ] Conformational polymorphism in a Schiff-base macrocyclic organic ligand: an experimental and theoretical study L. Lo Presti, R. Soave, M. Longhi and E. Ortoleva Synopsis: Two new polymorphs and a new solvated form of the Schiff-base macrocycle ligand C24H30N6 are reported. The molecular conformations and the packing features are analyzed both on geometrical and energetic grounds. Online 11 September 2010

Acta Cryst. (2010). B66, 544-558  [ doi:10.1107/S0108768110031873 ] Validation of experimental molecular crystal structures with dispersion-corrected density functional theory calculations J. van de Streek and M. A. Neumann Synopsis: The accuracy of a dispersion-corrected density functional theory method is validated against 241 experimental organic crystal structures from Acta Cryst. Section E. Online 11 September 2010

Acta Cryst. (2010). B66, 559-567  [ doi:10.1107/S0108768110026091 ] Charge density distribution in aminomethylphosphonic acid R. Janicki and P. Starynowicz Synopsis: The experimental charge density distribution in aminomethylphosphonic acid has been correlated with the theoretically calculated electronic structure of the molecule. A model of the P-O and P-C bonds is discussed. Online 4 September 2010

Acta Cryst. (2010). B66, 568-577  [ doi:10.1107/S0108768110026480 ] Validation of experimental charge densities: refinement of the macrolide antibiotic roxithromycin J. J. Holstein, P. Luger, R. Kalinowski, S. Mebs, C. Paulman and B. Dittrich Synopsis: Hydrogen disorder is revealed by validation of the experimental charge density of the macrolide antibiotic roxithromycin with invariom pseudoatom-database parameters. Although the figures of merit are almost unaffected, derived properties such as the electrostatic potential are shown to be in error when the disorder is not taken into account. Online 4 September 2010

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