Aperiodic crystals and superspace concepts

Aperiodic crystals may conveniently be described in a higher dimensional `superspace'. An overview of the method and applications to various families is given.

N—H⋯O and C—H⋯F hydrogen bonds in the incommensurately modulated crystal structure of adamantan-1-ammonium 4-fluorobenzoate

The incommensurately modulated crystal structure and the intermolecular interactions of the organic salt C₁₀H₁₈N⁺·C₇H₄FO₂⁻ are studied by analysing single-crystal X-ray diffraction data within the (3+1)-dimensional superspace approach and superspace group P2₁/n(α0γ)00.

The use of Mo Kα radiation in the assignment of the absolute configuration of light-atom molecules; the importance of high-resolution data

The use of Mo Kα radiation for the absolute structure determination of crystals made up of enantiopure light-atom molecules was explored. The combination of the methodologies described by Parsons and Hooft and the use of high-resolution reflections was found to be effective to achieve accurate values of the absolute structure parameters.

X-ray diffraction study of oxygen-conducting compounds Ln₂Mo₂O₉ (Ln = La, Pr)

The La₂Mo₂O₉ (LM) and Pr₂Mo₂O₉ (PM) single crystals are studied using precision X-ray diffraction and high-resolution transmission microscopy at room temperature.

Crystal structure and thermal expansion of Mn_1−xFe_xGe

A series of temperature-dependent single-crystal and powder diffraction experiments has been carried out using synchrotron radiation for the monogermanides of Mn, Fe and their solid solutions. The thermal expansion coefficient reaches its maximum for metastable MnGe, but no structural phase transition has been observed for any concentration of Mn_1−xFe_xGe in the temperature range 80–500 K.

Polymorphism in two biologically active di­hydropyrimidinium hydrochloride derivatives: qu­antitative inputs towards the energetics associated with crystal packing

The nature and energetics associated with the crystal packing of organic solids and its comparison between polymorphs consisting of charged species (cation and anion pairs) were addressed in detail utilizing crystallographic and computational approaches.

Mean bond-length variation in crystal structures: a bond-valence approach

The deficiencies present in the bond-valence theory in explaining mean bond-length variations observed in crystal structures can be overcome by taking into account the contribution of bond topology and bond strain to a constant bond-length value.

3-(4-Pyridyl)-acetylacetone – a fully featured substituted pyridine and a flexible linker for complex materials

3-(4-Pyridyl)-acetylacetone (HacacPy) may be used as an N donor ligand in coordination chemistry and in thermal degradation, and its metal complex Fe(acacPy)₃ can act as a poly(pyridine) bridge between two or three cations.

Similarities and peculiarities between the crystal structures of the hydrates of sodium sulfate and selenate

Salt hydrates of different water content and different crystal structures (Na₂SO₄·7H₂O, tetragonal, space group P4₁2₁2 and Na₂SeO₄·7.5H₂O, monoclinic, space group C2/c) can act mutually as a crystal nucleus, so that either of these salts can initiate crystallization of the other from their supersaturated solutions (a kind of heteroepitaxy). This phenomenon is attributed to similarities between particular elements of their structures.

Charge-density distribution in sodium bis­(4-nitro­phenyl)phosphate

The charge-density distribution in sodium bis(4-nitrophenyl)phosphate has been studied experimentally and by density-functional theory calculations.

Structure of decagonal Al–Ni–Rh

The crystal structure of the decagonal phase in the system Al–Ni–Rh (d-Al–Ni–Rh) was analyzed in the five-dimensional embedding approach based on single-crystal synchrotron X-ray diffraction data. The structure can be described as a quasiperiodic packing of partially overlapping decagonal and pentagonal columnar clusters with ∼ 21 Å diameter and ∼ 4 Å period along the tenfold axis.

Incommensurate modulations of relaxor ferroelectric Ca_0.24Ba_0.76Nb₂O₆ (CBN24) and Ca_0.31Ba_0.69Nb₂O₆ (CBN31)

CBN crystals are polymorphic with an orthorhombic one-dimensionally and a tetragonal two-dimensionally modulated superstructure.

Supramolecular structures and physicochemical properties of norfloxacin salts

Seven new molecular salts of norfloxacin were synthesized and structurally elucidated by single-crystal structure analysis. Physical and chemical properties were evaluated by a variety of analytical techniques.

Synthesis and structural characterization of donor-stabilized disubstituted di­phenyldi­thiophosphates of nickel(II)

Donor-stabilized addition complexes of nickel(II) with disubstituted diphenyldithiophosphates have been successfully isolated and characterized by various physico-chemical techniques and single-crystal X-ray analysis.

Structure of calcinaksite KNa[Ca(H₂O)][Si₄O_l0], the first hydrous member of the litidionite group of silicates with [Si₈O₂₀]⁸⁻ tubes

Calcinaksite is considered as a potential component of cements and concretes and a potential matrix for the immobilization of small molecules (in its channel system) and ions (on its cationic sites).

Sixth blind test of organic crystal-structure prediction methods

The sixth blind test of organic crystal-structure prediction methods is announced along with details of the format and how to participate.

High-Resolution Electron Microscopy

Introduction to Graphene-Based Nanomaterials: From Electronic Structure to Quantum Transport