Acta Crystallographica Section B

Structural Science

Volume 68, Part 5 (October 2012)

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

research papers

Acta Cryst. (2012). B68, 467-479  [ doi:10.1107/S0108768112019520 ] Cl-OH ion-exchanging process in chlorapatite (Ca5(PO4)3Clx(OH)1 - x) - a deep insight E. García-Tuñón, B. Dacuña, G. Zaragoza, J. Franco and F. Guitián Synopsis: Chlorapatite (ClAp) single crystals have been synthesized and described as stoichiometric with hexagonal structure. The heat treatment of these crystals at high temperature led to systematic structural modifications due to the Cl- by OH- anion replacement. Online 13 September 2012

Acta Cryst. (2012). B68, 480-492  [ doi:10.1107/S0108768112034027 ] Comparative modular analysis of two complex sulfosalt structures: sterryite, Cu(Ag,Cu)3Pb19(Sb,As)22(As-As)S56, and parasterryite, Ag4Pb20(Sb,As)24S58 Y. Moëlo, C. Guillot-Deudon, M. Evain, P. Orlandi and C. Biagioni Synopsis: The crystal structures of two complex minerals of the lead sulfosalt type, sterryite, Cu(Ag,Cu)3Pb19(Sb,As)22(As-As)S56, and parasterryite, Ag4Pb20(Sb,As)24S58, were solved and compared according to modular analysis. These quasi-homeotypic structures are expanded derivatives of owyheeite, Ag3Pb10Sb11S28. Online 13 September 2012

Acta Cryst. (2012). B68, 493-500  [ doi:10.1107/S010876811203042X ] Crystal structures of calcium hemicarboaluminate and carbonated calcium hemicarboaluminate from synchrotron powder diffraction data T. Runcevski, R. E. Dinnebier, O. V. Magdysyuk and H. Pöllmann Synopsis: The solution and refinement of the crystal structures of two cementitious phases formed at the beginning of the carbonation reaction of many building materials are reported. Online 17 August 2012

Acta Cryst. (2012). B68, 501-510  [ doi:10.1107/S0108768112033149 ] Theoretical hardness calculated from crystallo-chemical data for MoS2 and WS2 crystals and nanostructures M. I. Petrescu Synopsis: A theoretical hardness model based on crystallo-chemical data has permitted the separate calculation of Hmin (derived from weak bonds acting along the c axis), as well as Hmax [derived from strong bonds acting within the (0001) plane] in the space group P63/mmc anisodesmic compounds. Experimental hardness has confirmed the calculated Hmin. Online 17 August 2012

Acta Cryst. (2012). B68, 511-527  [ doi:10.1107/S0108768112030686 ] Unique thermodynamic relationships for fHo and fGo for crystalline inorganic salts. I. Predicting the possible existence and synthesis of Na2SO2 and Na2SeO2 Á. Vegas, J. F. Liebman and H. D. B. Jenkins Synopsis: Unique thermodynamic relationships for Na2SOx and Na2S2Ox salts, and prediction of the thermodynamic stability of Na2SO2 and Na2SeO2 and the connection with the oxidation-pressure concept are discussed. Online 13 September 2012

Acta Cryst. (2012). B68, 528-535  [ doi:10.1107/S0108768112032053 ] Topological studies of three related metal-organic frameworks of GdIII and 5-nitroisophthalate K. Davies, S. A. Bourne, L. Öhrström and C. L. Oliver Synopsis: Three gadolinium/5-nitroisophthalate metal-organic frameworks (MOFs) have been prepared under controlled but similar conditions. They are found to be related topologically through a simple C-C bond rotation. Online 17 August 2012

Acta Cryst. (2012). B68, 536-542  [ doi:10.1107/S0108768112037457 ] Four polymorphs (polytypes) of 5,6-dimethylbenzofurazan 1-oxide D. Britton, V. G. Young, W. E. Noland, M. J. Pinnow and C. M. Clark Synopsis: Four types of the title compound are identified, which differ in the stacking of planar layers of the nearly flat molecules. Polytypism is induced by variation of the conditions of crystallization. Online 13 September 2012

Acta Cryst. (2012). B68, 543-548  [ doi:10.1107/S0108768112034635 ] Structure of twisted BNC nanotubes with polygonal cross-section V. Blank, L. Ivanov, B. Kulnitskiy, I. Perezhogin, E. Polyakov and A. Semenov Synopsis: Twisted BNC nanotubes and nanofibers with polygonal cross-section have been synthesized in high isostatic pressure apparatus and analysed using transmission and scanning electron microscopy. Walls of these nanotubes contained fragments of both hexagonal and rhombohedral lattices. We propose mechanisms of nanotube structure formation and reasons for their deformation. Online 13 September 2012

Acta Cryst. (2012). B68, 549-557  [ doi:10.1107/S0108768112033484 ] Single-crystal investigation of L-tryptophan with Z' = 16 C. H. Görbitz, K. W. Törnroos and G. M. Day Synopsis: The crystal structure of the amino acid L-tryptophan has 16 molecules in the asymmetric unit, which are related by intriguing pseudosymmetry that led to exceptional systematic absences in the space group P1. Online 13 September 2012

Copyright © International Union of Crystallography
IUCr Webmaster