Acta Crystallographica Section A

Foundations of Crystallography

Volume 53, Part 2 (March 1997)

Cover illustration: A structural model of the decagonal Al-Pd-Mn quasicrystal, which consists of clusters represented by decagons and ten pentagons surrounding each decagon. This is obtained from a periodic structure in five-dimensional space by taking a three-dimensional section. Courtesy of A. Yamamoto.

obituaries
lead articles
research papers
book reviews
books received

obituaries

Acta Cryst. (1997). A53, 103-104 [doi:10.1107/S0108767396014249]

Arne Magnéli, 1914-1996

L. Kihlborg and I. Olovsson

Acta Cryst. (1997). A53, 105-107 [doi:10.1107/S0108767396014250]

Asbjørn Ivar Hordvik, 1928-1995

A. Authier

lead articles

Acta Cryst. (1997). A53, 108-143 [doi:10.1107/S0108767396011117]

Multiple-Beam X-ray Diffraction for Physical Determination of ReflectionPhases and its Applications

E. Weckert and K. Hümmer

Synopsis: Theoretical and experimental aspects of multibeam diffraction experiments for the determination of phase invariants are discussed. Results of its application to the enantiomorphism problem, non-periodic structures and small proteins are presented.

research papers

Acta Cryst. (1997). A53, 144-160 [doi:10.1107/S010876739601118X]

Order and Topology in Systems with Many Particles

V. A. Blatov and V. N. Serezhkin

Synopsis: A number of topological criteria for the presence or absence of short-range or long-range order in model systems of `gas' or `liquid' type and in crystal lattices are proposed.

Acta Cryst. (1997). A53, 161-167 [doi:10.1107/S0108767396012196]

General Expression for Probabilistic Examination of Multiphase Structure Invariants in the Case of a Native Protein and Multiple Derivatives. Application to Estimates of the Three-Phase Structure Invariants

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

Synopsis: A general probabilistic expression on n-phase invariants is presented for a native protein and m derivatives based on the concise formulae for three- and four-phase invariants. A method to improve estimation accuracy of three-phase invariants (3PSIs) is proposed that makes full use of all eight 3PSIs.

Acta Cryst. (1997). A53, 168-174 [doi:10.1107/S0108767396012378]

Effects of the Elastic Stress Relaxation on the HRTEM Image Contrast of Strained Heterostructures

L. De Caro, A. Giuffrida, E. Carlino and L. Tapfer

Synopsis: The effects of the elastic relaxation of compositional stresses caused by the finite size of transmission-electron-microscopy specimens on the image contrast of high-resolution transmission electron microscopy of strained heterostructures are investigated.

Acta Cryst. (1997). A53, 175-180 [doi:10.1107/S0108767396012755]

A Crystal Model for the Icosahedral Phase

W. Bian and Y. Zhu

Synopsis: A crystal model is proposed that is in good agreement with the experimental electron diffraction and high-resolution images of the icosahedral phase. The model has periodic transitional order with a unit cell (Im-3) containing 10 038 atoms and orientational order close to the m-3-5 point group.

Acta Cryst. (1997). A53, 181-186 [doi:10.1107/S010876739601327X]

Ultrasound-Induced Gradient Crystals Observed by High-Energy X-rays

K.-D. Liss, A. Magerl, A. Remhof and R. Hock

Synopsis: High-energy X-ray diffraction from a thick perfect silicon crystal with an applied longitudinal ultrasonic wave has been studied on a triple-crystal diffractometer. These measurements yield directly the distortion of the lattice in amplitude and direction. Tuneable intensity gains up to 50 and a controlled reciprocal phase space distribution of the scattering vector provides the basis for a novel X-ray optical element.

Acta Cryst. (1997). A53, 187-198 [doi:10.1107/S0108767396013335]

A Topological Analysis of Charge Densities in Diamond, Silicon and Germanium Crystals

Yu. A. Abramov and F. P. Okamura

Synopsis: The Hansen-Coppens multipole model of charge density has been fitted to highly accurate published experimental and theoretical structure factors for diamond, silicon and germanium crystals. Analysis of both experimental and theoretical charge densities using the resulting model parameters was performed in terms of Bader's topological theory.

Acta Cryst. (1997). A53, 199-201 [doi:10.1107/S0108767396013438]

Moiré Fringes and/or Translation-Fault Fringes?

M. Ohler, J. Härtwig and E. Prieur

Synopsis: The contradiction between the interpretation of interference fringes on X-ray diffraction topographs as translation-fault fringes or as moiré fringes is solved. What has been called translation-fault fringes is nothing but moiré fringes.

Acta Cryst. (1997). A53, 202-216 [doi:10.1107/S0108767396013517]

Analysis of Diffuse Scattering via the Reverse Monte Carlo Technique: a Systematic Investigation

Th. Proffen and T. R. Welberry

Synopsis: The viability of the reverse Monte Carlo method is systematically investigated using simulated disordered test structures as input.

Acta Cryst. (1997). A53, 217-224 [doi:10.1107/S0108767396013852]

A Procedure for the Clasification of Non-Organic Crystal Structures. I. Theoretical Background

H. Burzlaff and Y. Malinovsky

Synopsis: The paper deals with geometrical properties of crystal structures that are used to quantify the relationships among related structures. A method for establishing the similarity operators is introduced.

Acta Cryst. (1997). A53, 225-235 [doi:10.1107/S0108767396014353]

A Discrete Algorithm for Crystal Structure Prediction of Organic Molecules

D. W. M. Hofmann and T. Lengauer

Synopsis: The main features of the new algorithm are analysis of the molecule, discretization of the space, statistical atom-pair functions and clustering due to a similarity index.

Acta Cryst. (1997). A53, 236-241 [doi:10.1107/S0108767396014407]

Solving the Phase Problem of X-ray Diffraction Using Atomic Resolution X-ray Holograms

G. Xu

Synopsis: Simulation shows that, even without the phases, a structure can be recovered from the sample Bragg peaks modulated by a known crystal.

Acta Cryst. (1997). A53, 242-250 [doi:10.1107/S0108767396015243]

The Electrostatic Contribution to the Forward-Scattering Potential at a Space Charge Layer in High-Energy Electron Diffraction. II. Fringing Fields

R. E. Dunin-Borkowski and W. O. Saxton

Synopsis: The electrostatic potential is determined both inside and outside a parallel-sided dielectric slab that contains a space charge layer whose plane is perpendicular to the surfaces of the slab, with particular reference to the use of phase-contrast techniques in transmission electron microscopy to characterize such layers.

book reviews

Acta Cryst. (1997). A53, 251 [doi:10.1107/S0108767397099972]

Symmetry in chaos by M. Field and M. Golubitsky

Acta Cryst. (1997). A53, 251-252 [doi:10.1107/S0108767397099960]

Introduction to crystallographic statistics by U. Shmueli and G. H. Weiss

Acta Cryst. (1997). A53, 252 [doi:10.1107/S0108767397099959]

Symmetry of crystals: Introduction to International Tables for Crystallography Vol. A by T. Hahn and H. Wondratschek

books received

Acta Cryst. (1997). A53, 252 [doi:10.1107/S0108767397099947]

Molecular modeling of inorganic compounds edited by P. Comba and T. W. Hambley

Acta Cryst. (1997). A53, 252 [doi:10.1107/S0108767397099935]

Electrooptic effects in liquid crystal materials by L. M. Blinov and V. G. Chigrinov

Acta Cryst. (1997). A53, 252 [doi:10.1107/S0108767397099923]

Crystal identification with the polarizing microscope by R. E. Stoiber and S. A. Morse

Acta Cryst. (1997). A53, 252 [doi:10.1107/S0108767397099911]