Polysomatic apatites

The polysomatic apatite family A_5NB_3NO_9N + 6X_Nδ (2 ≤ N ≤ ∞) is built by condensing N apatite modules (A₅B₃O₁₈X_δ) in configurations to create B_nO_3n + 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.

A complicated quasicrystal approximant ∊₁₆ predicted by the strong-reflections approach

The structure of the quasicrystal approximant ∊₁₆ was predicted by the strong-reflections approach based on the known approximant ∊₆.

Structures of incommensurate and commensurate composite crystals Rb_xMnO₂ (x = 1.3711, 1.3636)

Incommensurate and commensurate composite crystals of Rb_xMnO₂ (x = 1.3711, 1.3636) have been studied by single-crystal X-ray diffraction.

Orientational disorder and phase transitions in crystals of dioxo­fluoromolybdate, (NH₄)₂MoO₂F₄

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.

Octahedral tilting in cation-ordered Jahn–Teller distorted perovskites – a group-theoretical analysis

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 Pr_1 − xCa_xMnO₃ (x ≃ 0.5), are also investigated.

Revision of the structure of Cs₂CuSi₅O₁₂ leucite as orthorhombic Pbca

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.

Structure solution of the new titanate Li₄Ti₈Ni₃O₂₁ using precession electron diffraction

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.

Concomitant polymorphic behavior of di-μ-thio­cyanato-κ²N:S;κ²S:N-bis­[bis­(tri-p-fluoro­phenyl­phosphine-κP)silver(I)]

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.

Ab initio structure determination of phase II of racemic ibuprofen by X-ray powder diffraction

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.

Zur Kristallchemie von Graphen und Graphit

The evidence of graphene being formed from pentavalent carbon augments the exceptional properties of this two-dimensional crystal.

Structures of dipeptides: the head-to-tail story

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.

A list of organic kryptoracemates

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.

Notes for authors 2010