This document describes the use of check2xsf for visualising charge densities etc. from CASTEP without the use of Materials Studio. CASTEP itself is not free code, and is available commercially from Accelrys, and to UK academics under a UKCP agreement. CASTEP itself is described on the castep.org WWW site. Unlike Materials Studio, the software described here all works under UNIX.
Especially if you are from outside Cambridge, do not ask the author of this document about Castep itself. Others are employed to answer such questions.
This document was originally written around XCrysDen, but Jmol is now a good choice as well.
(All the XCrysDen and Jmol screenshots were taken from copies run on an Alpha under Tru64, in order to demonstrate that this software really is portable.)
Also, a further page on cell manipulation using check2xsf.
All the examples use a program called check2xsf to convert the Castep .check file into something else. Version 1.04 (January 2012) can be downloaded as check2xsf.tgz, or one can browse an SVN repository and download the most recent tar file from the check2xsf SVN repository.
Although check2xsf was originally written to convert CASTEP .check files into XCrysDen .xsf files, it should be remembered that it can actually read .cell and .pdb files too, and write .cell, .cml, .pdb, .xyz and .cube files. So it can be used simply as a format converter for structures with no densities. It also reads .castep_bin and .orbitals files from CASTEP.
There is a separate page indexing other software by the same author, particularly involving manipulating EPS, PDFs and bitmaps images.