issue contents

ISSN: 2052-5206

February 2010 issue

Highlighted illustration

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].

feature articles

Acta Cryst. (2010). B66, 1-16
doi: 10.1107/S0108768109053981
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The polysomatic apatite family A5NB3NO9N + 6XNδ (2 ≤ N ≤ ∞) is built by condensing N apatite modules (A5B3O18Xδ) in configurations to create BnO3n + 1 (1 ≤ n ≤ ∞) tetrahedral chains. Hydroxyapatite [Ca10(PO4)6(OH)2] typifies the N = 2 polysome, but N = 3 A15(B2O7)3(BO4)3X3 (ganomalite) and N = 4 A20(B2O7)6X4 (nasonite) are also known.

research papers

Acta Cryst. (2010). B66, 17-26
doi: 10.1107/S0108768109053804
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The structure of the quasicrystal approximant ∊16 was predicted by the strong-reflections approach based on the known approximant ∊6.

Acta Cryst. (2010). B66, 27-33
doi: 10.1107/S0108768109053312
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Incommensurate and commensurate composite crystals of RbxMnO2 (x = 1.3711, 1.3636) have been studied by single-crystal X-ray diffraction.

Acta Cryst. (2010). B66, 34-39
doi: 10.1107/S0108768109052987
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Static and dynamic disorder in (NH4)2MoO2F4 was compared with that in (NH4)2WO2F4 at room temperature. Below the phase transition at 270 K the anionic sublattice of the former compound is statically disordered while it is fully ordered in the latter.

Acta Cryst. (2010). B66, 40-50
doi: 10.1107/S0108768109048010
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Group-theoretical methods have been used to examine the structures arising in ABX3 perovskites with Jahn–Teller (JT) active and non-JT active cations alternating on the B site. More complex patterns of ordering, as apparent in the structures of such perovskites as Pr1 − xCaxMnO3 (x ≃ 0.5), are also investigated.

Acta Cryst. (2010). B66, 51-59
doi: 10.1107/S0108768109054895
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High-resolution synchrotron X-ray and neutron powder diffraction have been used to refine the crystal structures of synthetic analogues of the mineral leucite with a stoichiometry of Cs2CuSi5O12.

Acta Cryst. (2010). B66, 60-68
doi: 10.1107/S010876810904631X
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The structure of the new titanate Li4Ti8Ni3O21 has been solved using precession electron diffraction. The refinement with synchrotron powder diffraction confirms the validity of the model and allows us to understand how Li, Ni and Ti are arranged over the cation sites.

Acta Cryst. (2010). B66, 69-75
doi: 10.1107/S0108768109048769
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The synthesis and characterization of [Ag2(SCN)2{P(4-FC6H4)3}4] have been reported. The crystallization of the compound from acetonitrile results in two concomitant polymorphic forms of different crystal shapes.

Acta Cryst. (2010). B66, 76-80
doi: 10.1107/S0108768109047363
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The crystal structure of phase II of racemic ibuprofen was solved ab initio from X-ray powder diffraction. Rietveld refinements were achieved with rigid-body constraints for the phenyl group and soft restraints on the other interatomic bond lengths and bond angles.

Acta Cryst. (2010). B66, 81-83
doi: 10.1107/S0108768109048216
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The evidence of graphene being formed from pentavalent carbon augments the exceptional properties of this two-dimensional crystal.

Acta Cryst. (2010). B66, 84-93
doi: 10.1107/S0108768109053257
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An analysis of the hydrogen-bonding arrangements in the crystal structures of dipeptides has led to a new classification scheme based on four basic patterns, each with two independent head-to-tail chains involving the terminal amino and carboxylate groups.

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A list of organic compounds that are racemic but that crystallize in Sohnke space groups (i.e. groups that include only proper symmetry operations) has been compiled and found to be larger than expected. The occurrence of pseudosymmetry relating the resolvable enantiomers has been studied.

international union of crystallography

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