XCrysDen

XCrysDen (X-Window Crystalline Structures and Densities) is a crystalline and molecular structure visualisation program, which displays isosurfaces and contours that can be superimposed on crystalline structures and interactively rotated and manipulated.

XCrySDen can run on most UNIX platforms, without any special hardware requirements and has been also ported to MAC OSX (requires X11) and Windows (requires CYGWIN).

References

1. Anton Kokalj "XCrySDen—a new program for displaying crystalline structures and electron densities", Journal of Molecular Graphics and Modelling 17 pp. 176-179 (1999)
2. Anton Kokalj "Computer graphics and graphical user interfaces as tools in simulations of matter at the atomic scale", Computational Materials Science 28 pp. 155-168 (2003)