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CD-ROM review - Crystallographic Space Group Diagrams and Tables'
CD-ROM compiled by Jeremy K. Cockcroft, Dept of Crystallography, Birkbeck College.
Written in html and conforms to the ISO9660 format.
Release date 5th August 1999. Price £9.95. Sales info.
I have always dreamed of owning a full set of Encyclopaedia Britannica. However, just as this seemed to be within my grasp, thirty two expensive volumes of gold-embossed leather were replaced by a thin (considerably cheaper) plastic box containing a couple of CDs. If there is any printed medium that has been revolutionised by the advent of the CD it is reference books such as encyclopaedias and dictionaries. And our community's equivalent - the spacegroup symmetry Tables - is no exception. The Tables were a prime candidate for transfer to CD, and Jeremy Cockcroft of Birkbeck College is to be congratulated for compiling this exceptional product at the extremely attractive price of £9.95.
The CD is written in html and will run on many different platforms via a web browser such as Netscape or Internet Explorer. A screen resolution of 1280x1024 or 1024x768 is required. Starting the CD is as simple as inserting it into your computer and opening the menu file using the browser. A list of known errata is published at http://img.cryst.bbk.ac.uk/sgp/ERRATA/ERRATA.HTM. Mounting instructions for Unix systems can be found at http://img.cryst.bbk.ac.uk/sgp/MOUNT.HTM
The CD contains the diagrams of the standard settings of all 230 spacegroups, as well as their symmetry operators and general reflection conditions. However, and extremely usefully for those of us who have struggled with this in the past, the CD also contains the same information for all possible alternative settings of axes, different choices of origin (10 are given for spacegroup I41/a!), enlarged C- and F-centred tetragonal cells, and R- and H- settings for trigonal systems. In addition, a simple click on the monoclinic spacegroup diagrams allows one to view them perpendicular to the unique axis. Each spacegroup diagram can be used (without permission) to other documents as high-resolution bitmaps, and the symmetry operators can be easily cut and pasted into other crystallographic software. A price reduction is available for bulk orders.
Despite the great deal of information contained on this CD, it would appear to still have a considerable amount of free space. The scope for adding additional information is thus huge. The equivalent Schoeflies symbols for each spacegroup would be useful, as would the subgroup/supergroup information contained in the current printed Tables. In a CD version, hyperlinks would enable one to move directly between the equivalently oriented spacegroups. For each spacegroup it would be extremely useful to have the special positions in each spacegroup setting, their Wyckoff symbols, multiplicities and the additional systematic absences they produce. And there is scope for reintroducing the structure factor equations omitted the most recent printed version of the Tables. However, I am sure the authors have thought of these and many other additions, and their omission in this version takes nothing from it.
So do I use this CD? Well, for spacegroup determination via systematic absences, and for finding simple information on standard settings of frequently used spacegroups I still instinctively reach for my battered printed version of the Tables. However, for any work involving non-standard settings or different origin choices, as frequently encountered when looking at subgroup/supergroup relationships, or for instructing students on the intricacies of origin shifts and axis permutations, this CD is a clear first choice. And in the future, with the CD's almost infinite capacity for holding additional information, I can see my printed Tables spending much more time in the bookcase. I recommend this CD to everyone without reservation.
M.I. McMahon, Dept. of Physics and Astronomy, The University of Edinburgh
Editor's Note
Full details are available on the World Wide Web at the
Guide book to the Space
group Diagrams and Tables, where a few of the diagrams can be freely seen.
Insstitutions can buy a site license for on-line access to all the diagrams.
Click here for
Sales information, including an order form and instructions for payment by credit card. A few
ERRATA are listed. You an also see
Instructions for
mounting the CD-ROM on a Linux system
Contact address for further information:
Dr Jeremy K. Cockcroft, Department of Crystallography, Birkbeck College,
Malet Street, London WC1E 7HX, United Kingdom.
Email: [email protected]
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