Software for pictures
There are a number of free software packages for creating crystallographic diagrams. They have their strengths and weaknesses and its worth trying different ones to find out what they can do, and what you are comfortable with.
The website www.ccp14.ac.uk contains links to a myriad of different packages, some of which are discussed here. All programs output files in a format suitable for journals (TIFF and EPS are the most common ones). Others permit output for the POV-RAY ray-tracer (www.pov-ray.org), producing visually stunning pictures. All programs are available from the X-ray Facility, and training in their use can easily be provided - contact Gary Nichol.
XP CAMERON
PLUTON
ORTEP
Gretep
Mercury
XP is the structure-plotting program which comes as part of the SHELXTL commercial package. We have a site licence and so the software is available to anyone on campus. It outputs files in Postscript and HPGL formats.
XP is often used for producing displacement ellipsoid plots (see right) and standard ball-and-stick plots. It's packing diagrams can quickly look cluttered and are not recommended. The diagrams are more functional than visually impressive and would not look particularly good on a poster, although it is often used to produce diagrams for papers, probably because of the popularity of SHELXTL. It is a rather old program, with output originally designed to be printed on pen-plotters. It is entirely keyboard and text-based command driven, which can make it seem impossible to use if you're used to a GUI and a mouse. Nevertheless it is a versatile program and people often learn to use it as part of learning to use SHELXTL.
CAMERON is the structure-plotting part of the CRYSTALS refinement and analysis package. This is written by Dr David Watkin, University of Oxford (www.xtl.oc.ac.uk), and is free for academic use. It tends to be used by users of CRYSTALS for producing molecular diagrams.
Like XP, CAMERON is a rather old program written many years ago when computer memory was tight. It is GUI-driven, but not interactive (in the sense that you can't use the mouse to drag the structure around), instead you have to select which direction you would like to rotate the structure, and by how many degrees.
CAMERON produces both molecular and packing diagrams. They tend to be rather colourful, although the choice of colour scheme (green for carbon!) is not considered to be standard (grey would be more conventional).
PLUTON is the graphical drawing arm of the multi-functional crystallographic software package PLATON. This free for academic use. UNIX versions are available from Professor Ton Spek, Utrecht University (www.cryst.chem.uu.nl) and the Windows implementation is available from Dr Louis Farrugia, University of Glasgow (www.chem.gla.ac.uk/~louis).
PLUTON produces a variety of different styles of diagram (ball & stick, packing diagrams, spacefill diagrams etc, but NOT ellipsoid plots) and has many options. It is worth spending some time trying them out to see which works best for you. As with CAMERON it is not interactive and the structure is rotated by selecting the direction of rotation and the degree of rotation from a menu.
One of the strengths of PLUTON is the variety of files it will output. Simple EPS files look like the picture at the top to the right, and are suitable for publications. However the program has a powerful range of options for exporting to POV-RAY with a variety of possibilities for styles and colours. The lower picture was traced with POV-RAY
ORTEP is the original ellipsoid-plotting program (although it plots other styles too), written some 40 years ago. The original code can be obtained from Dr Carroll Johnson, Oak Ridge National Laboratory (www.ornl.gov; ORTEP is Oak Ridge Thermal Ellipsoid Plotter) and the Windows implementaion is available from Dr Louis Farrugia, University of Glasgow (www.chem.gla.ac.uk/~louis).
As with PLUTON and CAMERON, ORTEP is not an interactive piece of software but again this is a result of the technology available when the program was written. It works on the same basis as CAMERON; the structure is rotated by a specified number of degrees in a specific direction. The EPS plots produced are rather functional, as opposed to eye-catching, and are mostly found in reports and papers not permitting colour. They are very similar in style to those produced by XP.
The most common use of ORTEP is in combination with POV-RAY to produce some truly stunning pictures for posters and presentations. The Windows version of ORTEP contains many options for custom-designing a plot for POV-RAY, including changing the background, lighting, shadows, atom colours, bond thickness and colours etc etc etc. The results are impressive, and one can easily spend most of a day experimenting with the different settings and options...
GRETEP is an interactive program combining the ellipsoid drawing of ORTEP with the colour scheme of CAMERON. GRETEP was written by researchers at the European Synchrotron Radiation Facility in Grenoble, France (hence GREnoble Thermal Ellipsoid Plotter) and is available from www.ccp14.ac.uk
Gretep is interactive in that the mouse is used to rotate and orient the structure, making positioning the molecules somewhat easier than other programs. There is also a function to output a file to POV-RAY although it is less powerful than the equivalent function in ORTEP. It's pictures are better suited to electronic papers, reports and presentations rather than posters.
Mercury is a program distributed along with the Cambridge Structural Database, but is also available free from the CCDC (www.ccdc.cam.ac.uk). It is a truely interactive program in that no use of the keyboard is needed and everything is mouse-driven.
Mercury's strengths lie in producing hydrogen-bonding diagrams and packing diagrams. It will create ball-and-stick, spacefill and ellipsoid plots too but the capped stick representation is the most effective. It allows the user to 'grow' the structure according to hydrogen bonding, or short contacts between molecules. Additionally it allows for the calculation of inter-atomic planes and inter-atomic distances and angles. If you're interested at all in examining crystal packing and hydrogen bonding in your compounds, learning how to use Mercury is a good idea.
