(IUCr) Contents for Acta Crystallographica Section B Vol. 63 Part 5 (October 2007)

Acta Cryst. (2007). B63, 675-682 [ doi:10.1107/S0108768107030005 ]

Structure and oxygen mobility in mayenite (Ca₁₂Al₁₄O₃₃): a high-temperature neutron powder diffraction study

H. Boysen, M. Lerch, A. Stys and A. Senyshyn

Synopsis: The crystal structure of mayenite is described as an aluminate framework filled with disordered calcium and `extra' oxygen. The high oxygen ionic conductivity at high temperatures proceeds via an exchange of the latter with framework oxygen.

Online 14 September 2007

Acta Cryst. (2007). B63, 683-692 [ doi:10.1107/S0108768107035021 ]

Inversion of 4f-states in CeB₆ thermally excited at 430 K

R. Makita, K. Tanaka, Y. Onuki and H. Tatewaki

Synopsis: The thermally excited electron-density distribution of CeB₆ measured at 430 K exhibited a significant electron population in Ce 5d- [Gamma] ₈ orbitals, which caused an inversion of 4f [Gamma] ₈- [Gamma] ₇ energy levels, in turn resulting in a greater electron population in 4f- [Gamma] ₇.

Online 14 September 2007

Acta Cryst. (2007). B63, 693-702 [ doi:10.1107/S0108768107037275 ]

Revision of pyrrhotite structures within a common superspace model

Z. Izaola, S. González, L. Elcoro, J. M. Perez-Mato, G. Madariaga and A. García

Synopsis: The structure of the pyrrhotite compound family has been reinvestigated in the framework of the superspace formalism. A common model with a unique superspace symmetry is also confirmed by first-principles calculations.

Online 14 September 2007

Acta Cryst. (2007). B63, 703-712 [ doi:10.1107/S0108768107038104 ]

Hexagonal ferrites: a unified model of the (TS)_nT series in superspace

I. Orlov, L. Palatinus, A. Arakcheeva and G. Chapuis

Synopsis: A large number of hexagonal ferrites can be derived from the Y ferrite Ba₂M₂Fe₁₂O₂₂ by introducing stacking faults. Structures with different compositions and lattice periodicity reaching hundreds of Ås are currently known. A single model based on the superspace approach is proposed which is able to fully describe the diversity of these structures.

Online 14 September 2007

Acta Cryst. (2007). B63, 713-718 [ doi:10.1107/S0108768107022197 ]

X-ray powder diffraction structural characterization of Pb_1 - xBa_xZr_0.65Ti_0.35O₃ ceramic

M. Mir, V. R. Mastelaro, P. P. Neves, A. C. Doriguetto, D. Garcia, M. H. Lente, J. A. Eiras and Y. P. Mascarenhas

Synopsis: The structure of Pb_1 - xBa_xZr_0.65Ti_0.35O₃ ceramic materials with 0.00 [less-than or equal to] x 0.40 was studied by synchrotron X-ray powder diffraction. The series shows a phase transition from rhombohedral to cubic at 543 and 463 K for x = 0.10 and 0.20, respectively, whereas the samples with x = 0.30 and 0.40 show a cubic structure from 10 to 450 K.

Online 14 September 2007

Acta Cryst. (2007). B63, 719-725 [ doi:10.1107/S0108768107037147 ]

Structure of RbFeO₂, refined from a reticular pseudomerohedrally twinned crystal with six domains

J. Nuss, N. Z. Ali and M. Jansen

Synopsis: A multiply twinned crystal of RbFeO₂ has been studied by single-crystal X-ray diffraction.

Online 14 September 2007

Acta Cryst. (2007). B63, 726-734 [ doi:10.1107/S0108768107039092 ]

Structure determination of structurally complex Ag₃₆Li₆₄ gamma-brass

T. Noritake, M. Aoki, S.- Towata, T. Takeuchi and U. Mizutani

Synopsis: The crystal structure of the Ag₃₆Li₆₄ gamma-brass was determined by Rietveld analysis of the synchrotron X-ray powder diffraction data. The bonding nature of the gamma-brass structure was clarified by analyzing the bond-length distribution.

Online 14 September 2007

Acta Cryst. (2007). B63, 735-747 [ doi:10.1107/S0108768107031758 ]

Synthesis, characterization and phase transitions in the inorganic-organic layered perovskite-type hybrids [(C_nH_2n + 1NH₃)₂PbI₄], n = 4, 5 and 6

D. G. Billing and A. Lemmerer

Synopsis: The thermochromic, reversible, first-order phase transitions in [(C_nH_2n + 1NH₃)₂PbI₄], n = 4, 5 and 6, were structurally characterized via single-crystal X-ray diffraction. The transitions are found to be associated with a concerted movement of both organic and inorganic components.

Online 14 September 2007

Acta Cryst. (2007). B63, 748-752 [ doi:10.1107/S0108768107041225 ]

Asymmetric hydrogen bonds in a centrosymmetric environment. III. Quantum mechanical calculations of the potential-energy surfaces for the very short hydrogen bonds in potassium hydrogen dichloromaleate

I. Majerz and I. Olovsson

Synopsis: According to earlier crystal structure determinations of potassium hydrogen dichloromaleate the H atoms are non-centered in the hydrogen bonds, although the environment is centrosymmetric. The experimental results have now been verified by quantum mechanical calculations of the potential-energy surfaces.

Online 14 September 2007

Acta Cryst. (2007). B63, 753-767 [ doi:10.1107/S0108768107030388 ]

Experimental charge density of L-alanyl-L-prolyl-L-alanine hydrate: classical multipole and invariom approach, analysis of intra- and intermolecular topological properties

R. Kalinowski, B. Dittrich, C. B. Hübschle, C. Paulmann and P. Luger

Synopsis: Topological and atomic properties of the tripeptide L-Ala-L-Pro-L-Ala hydrate were obtained from a full multipole refinement, an invariom transfer and from a theoretical calculation. They were quantitatively compared with each other and with results from the literature. The hydrogen-bond topology was critically examined via a comparison with promolecular densities.

Online 14 September 2007

Acta Cryst. (2007). B63, 768-782 [ doi:10.1107/S0108768107030996 ]

Knowledge-based model of hydrogen-bonding propensity in organic crystals

P. T. A. Galek, L. Fábián, W. D. S. Motherwell, F. H. Allen and N. Feeder

Synopsis: A new method is presented to predict which donors and acceptors form hydrogen bonds in a crystal structure, based on the statistical analysis of hydrogen bonds in the Cambridge Structural Database. The approach has potential application in identifying both likely and unusual hydrogen bonding, which can help to rationalize stable and metastable crystalline forms, of relevance to the drug development process in the pharmaceutical industry.

Online 14 September 2007

Acta Cryst. (2007). B63, 783-790 [ doi:10.1107/S010876810703652X ]

Structures of tetrabromothiophene and tetrabromoselenophene: the influence of the heteroatom on the heterophene packing

R. B. Helmholdt, E. J. Sonneveld, C. M. L. Vande Velde, F. Blockhuys, A. T. H. Lenstra, H. J. Geise and R. Peschar

Synopsis: The different phases and crystal structures of C₄Br₄S and C₄Br₄Se are explained on the basis of the close-packing of the Br atoms.

Online 14 September 2007

Acta Cryst. (2007). B63, 791-802 [ doi:10.1107/S0108768107033137 ]

Three-dimensional hydrogen-bonded frameworks in organic crystals: a topological study

I. A. Baburin and V. A. Blatov

Synopsis: Hydrogen-bonded frameworks in organic crystals have been classified into topological types of three-periodic nets. The relations between net topological types, space-group symmetry of crystals, site symmetry and point-group symmetry of molecules are discussed, and a set of rules for the crystal design of molecular frameworks is proposed.

Online 14 September 2007

addenda and errata

Acta Cryst. (2007). B63, 803 [ doi:10.1107/S0108768107044631 ]

Order-disorder transition in monoclinic sulfur: a precise structural study by high-resolution neutron powder diffraction. Corrigendum

W. I. F. David, R. M. Ibberson, S. F. J. Cox and P. T. Wood

Synopsis: A corrigendum to the paper by David et al. (2006), Acta Cryst. B62, 953-959.

Online 14 September 2007

Acta Crystallographica Section B

Structural Science

Volume 63, Part 5 (October 2007)

research papers

Structure and oxygen mobility in mayenite (Ca₁₂Al₁₄O₃₃): a high-temperature neutron powder diffraction study

H. Boysen, M. Lerch, A. Stys and A. Senyshyn

Inversion of 4f-states in CeB₆ thermally excited at 430 K

R. Makita, K. Tanaka, Y. Onuki and H. Tatewaki

Revision of pyrrhotite structures within a common superspace model

Z. Izaola, S. González, L. Elcoro, J. M. Perez-Mato, G. Madariaga and A. García

Hexagonal ferrites: a unified model of the (TS)_nT series in superspace

I. Orlov, L. Palatinus, A. Arakcheeva and G. Chapuis

X-ray powder diffraction structural characterization of Pb_1 - xBa_xZr_0.65Ti_0.35O₃ ceramic

M. Mir, V. R. Mastelaro, P. P. Neves, A. C. Doriguetto, D. Garcia, M. H. Lente, J. A. Eiras and Y. P. Mascarenhas

Structure of RbFeO₂, refined from a reticular pseudomerohedrally twinned crystal with six domains

J. Nuss, N. Z. Ali and M. Jansen

Structure determination of structurally complex Ag₃₆Li₆₄ gamma-brass

T. Noritake, M. Aoki, S.- Towata, T. Takeuchi and U. Mizutani

Synthesis, characterization and phase transitions in the inorganic-organic layered perovskite-type hybrids [(C_nH_2n + 1NH₃)₂PbI₄], n = 4, 5 and 6

D. G. Billing and A. Lemmerer

Asymmetric hydrogen bonds in a centrosymmetric environment. III. Quantum mechanical calculations of the potential-energy surfaces for the very short hydrogen bonds in potassium hydrogen dichloromaleate

I. Majerz and I. Olovsson

Experimental charge density of L-alanyl-L-prolyl-L-alanine hydrate: classical multipole and invariom approach, analysis of intra- and intermolecular topological properties

R. Kalinowski, B. Dittrich, C. B. Hübschle, C. Paulmann and P. Luger

Knowledge-based model of hydrogen-bonding propensity in organic crystals

P. T. A. Galek, L. Fábián, W. D. S. Motherwell, F. H. Allen and N. Feeder

Structures of tetrabromothiophene and tetrabromoselenophene: the influence of the heteroatom on the heterophene packing

R. B. Helmholdt, E. J. Sonneveld, C. M. L. Vande Velde, F. Blockhuys, A. T. H. Lenstra, H. J. Geise and R. Peschar

Three-dimensional hydrogen-bonded frameworks in organic crystals: a topological study

I. A. Baburin and V. A. Blatov

addenda and errata

Order-disorder transition in monoclinic sulfur: a precise structural study by high-resolution neutron powder diffraction. Corrigendum

W. I. F. David, R. M. Ibberson, S. F. J. Cox and P. T. Wood

Acta Crystallographica Section B

Structural Science

Volume 63, Part 5 (October 2007)

research papers

Structure and oxygen mobility in mayenite (Ca12Al14O33): a high-temperature neutron powder diffraction study

H. Boysen, M. Lerch, A. Stys and A. Senyshyn

Inversion of 4f-states in CeB6 thermally excited at 430 K

R. Makita, K. Tanaka, Y. Onuki and H. Tatewaki

Revision of pyrrhotite structures within a common superspace model

Z. Izaola, S. González, L. Elcoro, J. M. Perez-Mato, G. Madariaga and A. García

Hexagonal ferrites: a unified model of the (TS)nT series in superspace

I. Orlov, L. Palatinus, A. Arakcheeva and G. Chapuis

X-ray powder diffraction structural characterization of Pb1 - xBaxZr0.65Ti0.35O3 ceramic

M. Mir, V. R. Mastelaro, P. P. Neves, A. C. Doriguetto, D. Garcia, M. H. Lente, J. A. Eiras and Y. P. Mascarenhas

Structure of RbFeO2, refined from a reticular pseudomerohedrally twinned crystal with six domains

J. Nuss, N. Z. Ali and M. Jansen

Structure determination of structurally complex Ag36Li64 gamma-brass

T. Noritake, M. Aoki, S.- Towata, T. Takeuchi and U. Mizutani

Synthesis, characterization and phase transitions in the inorganic-organic layered perovskite-type hybrids [(CnH2n + 1NH3)2PbI4], n = 4, 5 and 6

D. G. Billing and A. Lemmerer

Asymmetric hydrogen bonds in a centrosymmetric environment. III. Quantum mechanical calculations of the potential-energy surfaces for the very short hydrogen bonds in potassium hydrogen dichloromaleate

I. Majerz and I. Olovsson

Experimental charge density of L-alanyl-L-prolyl-L-alanine hydrate: classical multipole and invariom approach, analysis of intra- and intermolecular topological properties

R. Kalinowski, B. Dittrich, C. B. Hübschle, C. Paulmann and P. Luger

Knowledge-based model of hydrogen-bonding propensity in organic crystals

P. T. A. Galek, L. Fábián, W. D. S. Motherwell, F. H. Allen and N. Feeder

Structures of tetrabromothiophene and tetrabromoselenophene: the influence of the heteroatom on the heterophene packing

R. B. Helmholdt, E. J. Sonneveld, C. M. L. Vande Velde, F. Blockhuys, A. T. H. Lenstra, H. J. Geise and R. Peschar

Three-dimensional hydrogen-bonded frameworks in organic crystals: a topological study

I. A. Baburin and V. A. Blatov

addenda and errata

Order-disorder transition in monoclinic sulfur: a precise structural study by high-resolution neutron powder diffraction. Corrigendum

W. I. F. David, R. M. Ibberson, S. F. J. Cox and P. T. Wood

Structure and oxygen mobility in mayenite (Ca₁₂Al₁₄O₃₃): a high-temperature neutron powder diffraction study

Inversion of 4f-states in CeB₆ thermally excited at 430 K

Hexagonal ferrites: a unified model of the (TS)_nT series in superspace

X-ray powder diffraction structural characterization of Pb_1 - xBa_xZr_0.65Ti_0.35O₃ ceramic

Structure of RbFeO₂, refined from a reticular pseudomerohedrally twinned crystal with six domains

Structure determination of structurally complex Ag₃₆Li₆₄ gamma-brass

Synthesis, characterization and phase transitions in the inorganic-organic layered perovskite-type hybrids [(C_nH_2n + 1NH₃)₂PbI₄], n = 4, 5 and 6