Foundations of Crystallography

 

Acta Cryst. (1999). A55, 1-13  [ doi:10.1107/S0108767398005108 ]

Nonsymmetrical X-ray diffraction in a perfect rectangular t  ×  l crystal. Extinction and absorption

G. Thorkildsen and H. B. Larsen

Synopsis: Nonsymmetrical diffraction in a perfect rectangular t × l crystal is analysed using the Takagi-Taupin equations. Analytical and numerical results are presented for the extinction and absorption factors..

Online January 1999

 

Acta Cryst. (1999). A55, 14-19  [ doi:10.1107/S0108767398006898 ]

Temperature-dependent X-ray dynamical diffraction: Darwin theory simulations

J.-S. Chung and S. M. Durbin

Synopsis: Darwin theory is used for computer simulations of diffraction from perfect Si and Ge crystals with thermal vibrations. Dynamical theory with a Debye-Waller factor fits most results, but deviations at high temperature call into question the usual quasi-ergodic hypothesis.

Online January 1999

 

Acta Cryst. (1999). A55, 20-29  [ doi:10.1107/S010876739800717X ]

Resonant X-ray diffraction in incommensurately modulated crystals. Symmetry consideration of anisotropic anomalous scattering

E. N. Ovchinnikova and V. E. Dmitrienko

Synopsis: It is shown that the additional ATS main reflections and ATS satellites can appear in the diffraction pattern of an incommensurately modulated crystal when the wavelength of the incident X-radiation is close to the absorption edge.

Online January 1999

 

Acta Cryst. (1999). A55, 30-47  [ doi:10.1107/S0108767398007181 ]

Influence of intermolecular interactions on multipole-refined electron densities

M. A. Spackman, P. G. Byrom, M. Alfredsson and K. Hermansson

Synopsis: Model X-ray data are computed from a superposition of ab initio molecular electron densities in the crystal, as well as from periodic crystal Hartree-Fock electron densities, for several hydrogen-bonded systems and the weakly bound acetylene. Interaction effects on the electron density are illustrated and retrieved quantitatively by suitable multipole models. Multipole refinement reveals enhancement of the molecular dipole moment for hydrogen-bonded crystals but negligible change in molecular second moments. Electric field gradients at H nuclei are also discussed.

Online January 1999

 

Acta Cryst. (1999). A55, 48-57  [ doi:10.1107/S0108767398007272 ]

The periodic average structure of particular quasicrystals

W. Steurer and T. Haibach

Synopsis: Particular quasiperiodic structures with non-crystallographic symmetry exhibit discrete periodic average structures. Examples for one-, two- and three-dimensional quasiperiodic structures are discussed.

Online January 1999

 

Acta Cryst. (1999). A55, 58-64  [ doi:10.1107/S0108767398007521 ]

Minimal surfaces with self-intersections along straight lines. I. Derivation and properties

E. Koch and W. Fischer

Synopsis: A new procedure for the derivation of minimal surfaces with self-intersections along straight lines is introduced. The deduction of several properties of each such surface from its generating polygon is described.

Online January 1999

 

Acta Cryst. (1999). A55, 65-69  [ doi:10.1107/S0108767398007594 ]

Comments on the characteristics of incommensurate modulation in quartz: discussion about a neutron scattering experiment

T. A. Aslanyan, T. Shigenari and K. Abe

Synopsis: From the analysis of the elastic neutron scattering data by Dolino et al. [J. Phys. (Paris) (1984), 45, 361-371], it is shown that in the incommensurate (IC) phase of quartz there exists a strong component of the acoustic displacements of the modulation. The existence of a large is not consistent with the currently accepted model and a new model is needed in order to understand the origin of the IC modulation in quartz.

Online January 1999

 

Acta Cryst. (1999). A55, 70-83  [ doi:10.1107/S0108767398007909 ]

A multisolution method of phase determination by combined maximization of entropy and likelihood. VI. The use of error-correcting codes as a source of phase permutation and their application to the phase problem in powder, electron and macromolecular crystallography

C. Gilmore, W. Dong and G. Bricogne

Synopsis: Error-correcting codes are used to permute phases in a maximum-entropy-likelihood environment. The method is applied to powder, electron diffraction and protein data.

Online January 1999

 

Acta Cryst. (1999). A55, 84-94  [ doi:10.1107/S0108767398008897 ]

On the prediction of crystal morphology. III. Equilibrium and growth behaviour of crystal faces containing multiple connected nets

R. F. P. Grimbergen, P. Bennema and H. Meekes

Synopsis: Using Monte Carlo simulations, the equilibrium and growth behaviour of crystal faces having more than one connected net are studied. The crystal habit is in such cases dependent on the supersaturation. Flat, rough and disordered flat phases are found.

Online January 1999

 

Acta Cryst. (1999). A55, 95  [ doi:10.1107/S0108767398011623 ]

A practical guide to phase retrieval and the reconstruction of analytic functions from measurements of their absolute values

Online January 1999

 

Acta Cryst. (1999). A55, 95  [ doi:10.1107/S0108767398012306 ]

Local structure from diffraction

Online January 1999

 

Acta Cryst. (1999). A55, 96-101  [ doi:10.1107/S0108767398015414 ]

International Union of Crystallography Acta Crystallographica Section A
> Notes for Authors

Online January 1999

 

Acta Cryst. (1999). A55, 102  [ doi:10.1107/S0108767398016912 ]

International Union of CrystallographyTransfer of Copyright Agreement

Online January 1999