IUCr activities
[Henri Levy]Figure 1: Henri Levy of Oak Ridge National Laboratory at the keyboard of the four-circle Picker X-ray diffractometer, and the PDP-5 computer that was programmed to control it. (Photograph courtesy of ORNL)

Computing commission

The 8th edition of the IUCr Computing Commission Newsletter is available online as a PDF file at the CompComm website. In the computing monograph of the 1950 crystallographic computing school, Ray Pepinksy stated “records of what has been considered and what has been accomplished are essential to the proper development of this or any other field.”(1) With this in mind, the main theme for this edition is that of ‘Crystallographic Computing at Oak Ridge National Laboratory: 1954 to 1968’ with an article by William Busing (refer figure 1). This is followed by stereoscopic structure drawings as generated by Carroll Johnson in the mid 1960’s using ORTEP-I (Oak Ridge Thermal Ellipsoid Plot software) for the joint ACA and MSA meeting, Gatlinburg, TN, USA, 1965, and the Second Biophysical Congress, Vienna, Austria, 1966.

Václav Petříček and Michal Dušek describe some of the new features in the latest version of the Jana single crystal and powder diffraction structure refinement program. This includes the enhanced ability to simultaneously use multiple single crystal and powder diffraction datasets; Magnetic scattering, Coelho and Cheary based fundamental parameters profile fitting; and an interface to the SuperFlip structure solution software for incommensurate and commensurate crystal structures. Brian Toby and Bob Von Dreele report on the conclusions of the GSAS-II workshop held in May 2007 where the aim was to build on the influential and popular GSAS program of Larson and Von Dreele to create a GSAS-II from scratch using the latest algorithms and software development methods. Luc Bourhis, Ralf Grosse-Kunstleve and Paul Adams give the latest CCTBX developments. While the open-source CCTBX project has traditionally concentrated on macromolecular crystallography, the inclusion of algorithms specifically for small-molecule work are described, as are other new features and capabilities.

[Pole figures]c
[Polymer diffraction]d

Figure 2: Examples using the MAX3D reciprocal space viewer: (a) LuFe2O4 at 80C; (b) diffuse scattering perpendicular to the c-axis in Hexanaphthylbenzene; (c) all pole figures observed at once in Au/Pt nanolayered rolled sheets; (d) diffraction of a polymer mapped into reciprocal space.
Branton Campbell, John Evans, Francesca Perselli and Harold Stokes describe the method of Rietveld refinement of structural distortion-mode amplitudes using the Isotropy program and the Topas software. A tutorial is included based on Tungsten Trioxide. It describes the “minimum ‘four clicks’ required [in Topas Academic] to prepare and perform a distortion-mode refinement” where one uses “just 5 structural degrees of freedom rather than the 24 parameters of a conventional refinement.” Jim Britten and Weiguang Guan showcase the MS-Windows and Linux based MAX3D software for the Visualization of Reciprocal Space Volumes. The images displayed in the article reminds one of images from the Hubble Space Telescope. The MAX3D article gives impressive examples of what most users of single crystal apparatus are missing in potentially understanding their data and consequent structural implications. A number of reciprocal space volumes generated by MAX3D are included in figure 2.

As an addendum, a variety of historical software reports, with original source code, are included courtesy of ORNL as a separate PDF file. These include the reports on crystallographic programs for the IBM 704, plus ORABS, ORFLS, ORFFE, ORTEP-I and ORTEP-II.

The next edition of the newsletter is expected to be in mid to late 2009 (not 2008 due to it being an IUCr congress year). Articles of interest to the crystallographic computing community are very welcome and can be sent to the newsletter editor at lachlan.cranswick@nrc.gc.ca. Previous editions of the newsletter are also available via the Computing Commission website at www.iucr.org/iucr-top/comm/ccom/.

Lachlan Cranswick


[1] Pepinsky, R., (1952b). Computing Methods and the Phase Problem in X-ray Crystal Analysis, edited by R. Pepinsky, Foreward, State College, PA, USA: Dept. of Physics, The Pennsylvania State College.