The following guides are available:

On-line Documentation and Downloadable User Guide

The complete online CASTEP Documentation and the downloadable CASTEP User Guide (200+ page PDF) from Materials Studio - created by Dassault Systèmes BIOVIA.


CASTEP has a built-in keyword help system. To get more information on CASTEP use:
castep -help
Alternatively you can search for help on a particular topic
castep -help search keyword
or list all of the input parameters
castep -help all

Full lists of all input parameters can be found in the Dassault Systèmes BIOVIA documentation