Fifth issue of the IUCr Computing Commission newsletter

L. Cranswick lzc at
Thu Jan 27 10:54:53 EST 2005

The latest IUCr Computing Commission newsletteris viewable via:

Besides having articles of general interest, this edition has
the theme:

 "At Right Angles to Conventional Crystallographic reality:
 incommensurate structures, quasicrystals and pair distribution

   - Editors: Simon Billinge, Gervais Chapuis, Lachlan Cranswick 
              and Ron Lifshitz

The Editors Introduction and list of articles in this edition is given



Since more than three decades, crystallographers have been faced with
new challenging crystalline material with structures incompatible with
the classical view of crystals with three dimensional periodicity. These
new materials includes incommensurately modulated and composite
structures, quasicrystals with icosahedral or dodecagonal symmetry to
cite only the most representative examples of aperiodic structures as
they are presently called. In most cases, these new structures are best
described by embedding them in space of up to six dimensions. This
approach is justified by the fact that periodicity can be recovered
although in higher dimension. 

The rapid evolution of this field is not only due to the innovative
theoretical approach of the so called superspace symmetry but also to
the enormous worldwide efforts on software development. This issue
includes a range of articles on techniques that can explain diffraction
data where the most appropriate model may not fit into an ordered
convenient commensurate cell: Incommensurate Structures, Quasicrystals
and Pair Distribution Functions. Besides encouraging exchange of ideas
within different communities, we hope it might encourage
crystallographers, who may prefer to deal only with ordered commensurate
cells, to take these style of problems out of the "too unusual draw" and
onto their diffractometers and transmission electron microscopes.


At Right Angles to Conventional Crystallographic reality: incommensurate
structures, quasicrystals and pair distribution functions (programming
and general articles) :

 Procedures for the refinement of incommensurate structures using XND.
 Coding issues for the refinement of incommensurate structures -
 Jean-Francois Berar and Gianguido Baldinozzi 

 A Program Package for Aperiodic Tilings - Uwe Grimm 

 DIMS (Direct-methods program for solving Incommensurate Modulated
 Structures) on the VEC platform - Hai-fu Fan 

 DIMS (Direct-methods program for solving Incommensurate Modulated
 Structures) /VEC applications - Hai-fu Fan 

 Collection and visualization of single crystal data of incommensurate
 crystals - Rob Hooft 

 Visualization and Analysis of Single Crystal Time-of-Flight Neutron
 Scattering Data using ISAW - Dennis Mikkelson, Arthur J. Schultz, Ruth
 Mikkelson and Thomas Worlton 

 Graphical and interpretation tools for difficult incommensurate and
 composite structures in JANA2000 - Vaclav Petricek and Michal Dusek 

 Calculating the Pair Distribution Function from a Structural Model -
 Thomas Proffen 


Other Articles :

 Refinement in Crystals - Richard Cooper and David Watkin 

 cctbx news: Phil and friends - Ralf W. Grosse-Kunstleve, Pavel V.
 Afonine, Nicholas K. Sauter and Paul D. Adams 

 Computing the Z-matrix for global optimisation - Kenneth Shankland 


Lachlan M. D. Cranswick
Contact outside working hours /
  Coordonnees en dehors des heures de travail:
E-mail / courriel: lachlan at   Home Tel: (613) 584-4226
Mobile/Cell: 613 401 3433   WWW:
        P.O. Box 2057, Deep River, Ontario, Canada, K0J 1P0

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