XCrySDen is a crystalline and molecular structure visualisation program,
which aims at display of isosurfaces and contours, which can be
superimposed on crystalline structures and interactively rotated and
manipulated. It can run on most UNIX platforms, without any special hardware requirements.
Here is the simplest installation procedure for xcrysden installation.
The general method for Ubuntu has been given in this post.
Here is the simplest method of all.
