Foundations of Crystallography

 

Acta Cryst. (2001). A57, 1-3  [ doi:10.1107/S0108767300015440 ]

André Guinier (1911-2000)

M. Lambert

Online January 2001

 

Acta Cryst. (2001). A57, 4-19  [ doi:10.1107/S0108767300010680 ]

The crystal problem for polytypes

D. P. Varn and G. S. Canright

Synopsis: The question of crystalline ground states for polytypes is considered, using reasoning based on the symmetries of the modular layers. It is found that polytypes in the SiC family must have crystalline ground states; but this conclusion does not hold for the other families studied (CdI₂, GaSe, micas and kaolins).

Online January 2001

 

Acta Cryst. (2001). A57, 20-33  [ doi:10.1107/S0108767300011326 ]

A geometric centroid principle and its application

F. Mädler, E. Behrends and K. Knorr

Synopsis: A fundamental geometric principle opens up non-classical qualitative ways of investigating orientational disorder.

Online January 2001

 

Acta Cryst. (2001). A57, 34-39  [ doi:10.1107/S0108767300011521 ]

Structural units of cuprates in natural Cu-oxysalts

L. Leonyuk, V. Maltsev, G.-J. Babonas, R. Szymczak, H. Szymczak and M. Baran

Synopsis: Copper oxysalt minerals are considered as the salts of hypothetical copper acids with characteristic Cu-containing structural units. Magnetic susceptibility data for a series of minerals were analyzed from the viewpoint of the developed extended structural classification scheme for cuprates.

Online January 2001

 

Acta Cryst. (2001). A57, 40-46  [ doi:10.1107/S0108767300011818 ]

The method of joint probability distribution functions applied to the one-wavelength anomalous-scattering (OAS) case

C. Giacovazzo and D. Siliqi

Synopsis: The joint probability distribution method is applied to define phases for the one-wavelength anomalous-scattering techniques.

Online January 2001

 

Acta Cryst. (2001). A57, 47-54  [ doi:10.1107/S0108767300012174 ]

A probabilistic approach to space-group determination from powder diffraction data

A. J. Markvardsen, W. I. F. David, J. C. Johnson and K. Shankland

Synopsis: The determination of the space-group symmetry of a crystal from powder diffraction data is placed on a quantitative basis using an algorithm based upon probability theory.

Online January 2001

 

Acta Cryst. (2001). A57, 55-59  [ doi:10.1107/S0108767300012733 ]

Estimation of individual phases from the four-phase structure invariants in the single isomorphous replacement case

N.-H. Hu, Y.-S. Liu and S.-Y. Wang

Synopsis: A method is presented that can be used to estimate some individual phases with special values of 0, or using the SIR data in macromolecular structure determination.

Online January 2001

 

Acta Cryst. (2001). A57, 60-67  [ doi:10.1107/S0108767300012915 ]

Structure refinement of the silicon carbide polytypes 4H and 6H: unambiguous determination of the refinement parameters

A. Bauer, P. Reischauer, J. Kräusslich, N. Schell, W. Matz and K. Goetz

Synopsis: `Quasiforbidden' reflections are utilized for an unambiguous determination of structure refinement parameters of the silicon carbide polytypes 4 and 6. The determination was accomplished by a comparison of measured and calculated Renninger scans close to three-beam nodes.

Online January 2001

 

Acta Cryst. (2001). A57, 68-75  [ doi:10.1107/S0108767300013180 ]

Forbidden X-ray wavefields of three-beam Bragg reflections from thick crystals

X. R. Huang, M. Dudley and J. Y. Zhao

Synopsis: A detailed analysis of a three-beam diffraction dispersion surface is performed to study the forbidden wavefields of thick-crystal reflections. It is demonstrated that Bragg-case three-beam diffraction from thick crystals can be regarded as either a four-mode diffraction process for Bragg-Laue geometry or a two-mode process for Bragg-Bragg geometry.

Online January 2001

 

Acta Cryst. (2001). A57, 76-86  [ doi:10.1107/S0108767300013155 ]

Wavefunctions derived from experiment. I. Motivation and theory

D. Jayatilaka and D. J. Grimwood

Synopsis: The concept of extracting wavefunctions from experimental data is critically examined and past efforts are reviewed. A general and systematically improvable method for fitting a wavefunction to experimental data is also proposed.

Online January 2001

 

Acta Cryst. (2001). A57, 87-100  [ doi:10.1107/S0108767300013167 ]

Wavefunctions derived from experiment. II. A wavefunction for oxalic acid dihydrate

D. J. Grimwood and D. Jayatilaka

Synopsis: A wavefunction has been calculated for the oxalic acid dihydrate molecule using accurate low-temperature X-ray charge-density data. Derived properties from the constrained Hartree-Fock wavefunction fragments are also presented.

Online January 2001

 

Acta Cryst. (2001). A57, 101-109  [ doi:10.1107/S0108767300013659 ]

Diffuse X-ray scattering from benzil, C₁₄H₁₀O₂: analysis via automatic refinement of a Monte Carlo model

T. R. Welberry, D. J. Goossens, A. J. Edwards and W. I. F. David

Synopsis: A recently developed method for fitting a Monte Carlo computer simulation model to observed single-crystal diffuse X-ray scattering data has been used to study the diffuse scattering in benzil. The analysis has shown that the diffuse lines, which feature so prominently in the observed diffraction patterns, are due to strong longitudinal displacement correlations transmitted from molecule to molecule via a network of contacts involving hydrogen bonding.

Online January 2001

 

Acta Cryst. (2001). A57, 110-111  [ doi:10.1107/S010876730001151X ]

The invariant cubic rod (cylinder) packings: symmetries and coordinates

M. O'Keeffe, J. Plévert, Y. Teshima, Y. Watanabe and T. Ogama

Synopsis: There are six homogeneous cubic packings of non-intersecting rods (cylinders) with the positions of the axes fixed by symmetry (invariant). Their symmetries and coordinates are given.

Online January 2001

 

Acta Cryst. (2001). A57, 112-113  [ doi:10.1107/S0108767300010874 ]

On the symmetry of 4- to 11-hedra

Y. L. Voytekhovsky

Synopsis: A table giving the statistics of the visible symmetry point groups for all non-isomorphic 4- to 8-hedra and simple 9- to 11-hedra is presented.

Online January 2001

 

Acta Cryst. (2001). A57, 114-115  [ doi:10.1107/S0108767300013271 ]

Coset and double-coset decompositions of the magnetic point groups

J. Schlessman and D. B. Litvin

Synopsis: Mathematical properties of crystallographic magnetic point groups are tabulated.

Online January 2001

 

Acta Cryst. (2001). A57, 116-117  [ doi:10.1107/S0108767300013179 ]

A pseudoinverse for Frank's formula

A. Gómez and D. Romeu

Synopsis: The Moore-Penrose generalized inverse to Frank's formula for grain boundary dislocation content is derived using a simple vector approach.

Online January 2001

 

Acta Cryst. (2001). A57, 118  [ doi:10.1107/S0108767300019218 ]

General formalism for phase combination and phase refinement: a statistical thermodynamics approach in reciprocal space. Erratum

M. Delarue and H. Orland

Synopsis: Erratum to Acta Cryst. (2000), A56, 562-574.

Online January 2001

 

Acta Cryst. (2001). A57, 119-124  [ doi:10.1107/S0108767300016329 ]

Notes for Authors

Online January 2001