Available from: Crystal Impact, K. Brandenburg & M. Berndt GbR, Postfach 1251, D-53002 Bonn, Germany (tel. +49 228 73 5825; e-mail: sales@crystalimpact.de; WWW: http://www.crystalimpact.de). Current version: 2.1b. Price: Single license 998.00 or US $1100.00. Additional users: 498.00 or US $550.00. Site licence (per department): 1998.00 or US $2200.00. In all cases there is a 50% academic discount.

DIAMOND - Visual Crystal Structure Information System is a Windows-based graphics program (Windows 95 or higher required) for drawing crystal structures. Installation of the program is simple and straightforward. Although no written manual is provided in either hard-copy or electronic form (a minor drawback), a tutorial is available that is quite helpful in getting started. An online manual is also available, and provides ready answers to most questions that arise. Additional support is provided through the Internet (http://www.crystalimpact.de/diamond/support.htm) or through direct electronic correspondence (support@crystalimpact.de). A database of 40 mineral structures provides numerous examples of the capabilities of the program.

DIAMOND features a split-screen format with the left portion of the screen serving as the structure window and the right portion being a `data sheet' containing useful crystallographic information such as crystal system and space group, lattice dimensions, atomic coordinates, vibrational displacement parameters and selected geometric parameters. The relative sizes of these two windows can be readily adjusted through mouse repositioning of a `splitter'. Numerous options for structure construction and manipulation are available. On-screen buttons, supplemented by balloon help messages, contain intuitive symbols to indicate their function, and more advanced operations can be accomplished through a variety of pull-down menus. The structure and data-sheet windows are coupled, and selections or adjustments made in one are immediately reflected in the other.

Data can be input manually, but the program also reads a variety of standard formats. Expansion of this list, for example to all commercially available packages that are typically used, would be a welcome addition, but availability of a free format read allows for adequate interaction with most. Structure development is accomplished through functions to expand molecular fragments, fill unit cells, display multiple unit cells, complete user-defined coordination spheres and delete nonbonded atoms or whole fragments.

Structure representation can be toggled between a stick diagram, stick and ball, space-filling spheres and thermal ellipsoids. Presentation can be made in either a draft-quality flat mode or a more realistic render mode. Rotation and orientation of the structure are easily accomplished with menu buttons for `X/Y rotation', `Z rotation', `center of rotation definition', and `shift' for structure repositioning within the window. Analysis of structural detail is facilitated by a `zoom' function. On the very low-end Pentium system used for this review (120 MHz), rotation function on all but the stick diagram was rather slow and jerky; however, dramatic improvement would be expected with even moderate system enhancement.

DIAMOND was specifically written for inorganic structures and its features for displaying these in polyhedral format are a strength of the program. Various polyhedron formats are available, and the definition and design of these, based on the central atom, is straightforward and easy. The definition and inclusion of `dummy atoms' provides a particularly useful tool for many of these types of structures. Combined with the structure-development features described above, nice quality packing diagrams of even very complicated inorganic structures can be produced with a minimum of input. Once constructed, the structure can be examined from various directions through a pull-down menu for this purpose.

Although written for inorganic structures, DIAMOND is equally useful for viewing molecular compounds or even proteins, and is especially good for those involving significant intermolecular interactions, such as hydrogen bonding. Connectivities can be defined for a variety of criteria, in order to distinguish between types of interactions present in a structure. A fragment selection feature is especially useful, as whole supramolecular features can be highlighted.

The wide variety of functions available in DIAMOND make it a powerful tool for both teaching and research. Its modest price and substantial academic discount warrant its consideration for any crystallographic teaching laboratory, and the planned release of a `student' edition will make it even more attractive.