Double-helix structure in multiwall boron nitride nanotubes

Electron nanodiffraction and high-resolution imaging evidence is presented to support a new structural form of multiwall boron nitride nanotubes that consist of two helices; one is highly crystalline and faceted and the other is circular and less ordered.

Combinatorial construction of tilings by barycentric simplex orbits (D symbols) and their realizations in Euclidean and other homogeneous spaces

A new method is presented which decides algorithmically whether a combinatorial space tiling is realizable in Euclidean space or in other homogeneous geometries.

Anomalous scattering factor determined by semicircle fitting near the K-absorption edge of Ge

A method for the determination of anomalous scattering factors very near to an absorption edge is proposed using their semicircular behavior. As an example, Ge anomalous scattering factors are determined, which show excellent agreement with the values determined by two other methods.

Ultra-small-angle X-ray scattering from dislocation structures

Ultra-small-angle X-ray scattering data were obtained from deformed single-crystal aluminium samples. These data are consistent with recent theoretical predictions of scattering from dislocation walls, allowing quantitative microstructural parameters to be extracted.

Ab initio structure determination using dispersive differences from multiple-wavelength synchrotron-radiation powder diffraction data

A theoretical foundation and test-case evaluation is presented for de novo structure determination using f′ difference techniques. Prospects for extension of these methods to larger molecules than are currently tackled, including proteins, and the possible use of softer X-rays are discussed.

Report of the Working Group on Crystal Phase Identifiers

The proposed crystalline phase identifier consists of a number of components (layers) describing enough properties of the phase to allow a unique identification. These layers consist of the chemical formula, a flag indicating the state of matter, the space-group number and the Wyckoff sequence. They are defined in such a way that they can be incorporated into the IUPAC International Chemical Identifier (InChI) proposed by the International Union of Pure and Applied Chemistry (IUPAC).

The variety of convex 12-hedra revised

The symmetry point group statistics for all combinatorially non-isomorphic convex 12-hedra (6384634 in total) are contributed in the paper. The numbers of 12-hedra with 11 to 19 vertices are revised.

On the Motzkin–Grünbaum theorem

A constructive proof of the Motzkin–Grünbaum theorem (at least one fullerene C_n with any even n ≥ 24 exists) is suggested

Report of the Executive Committee for 2004

Prices of IUCr journals