MJR's Castep Notes

This page contains some random information about the use of Castep. It is incomplete, but contributions are welcome. It is provided mostly so that I can remember what I have done, and in the hope that it might be of some use to someone else.

(I also have unmaintained notes on the ancient, Fortran77, pre-commercial version of Castep. In the unlikely event that someone wants these, they can still be found here.)

Utilities

The Castep distribution provides many useful utilities. Some it does not include:

• check2xsf, a converter for Castep's check files, and can extract charge and spin density, wavefuctions, or simply atomic positions. It can also convert between .cell and .pdb files, and other similar tricks.
• cellsym, a simple command-line interface to the spglib crystal symmetry finder which reads Castep .cell files (amongst other formats).

Theory

These notes should mostly apply to plane-wave codes in general, not just Castep, but I make no promises.

• Some notes on Bloch's Theorem.
• Some notes on interpolation and real-space integration of functions expressed in reciprocal space. Titled "Castep and Real Space Integrals" for brevity.

Practice

A simple test of Castep on an ethene molecule.

Over-riding FFT grid selection

I often find myself wanting to do this, for various strange reasons. It seems to be undocumented and unsupported, but, in a .param file, a block such as the following seems to work.

%block devel_code 
STD_GRID=50 50 45 FINE_GRID=60 60 50
%endblock devel_code

Useful Links

• castep.org, including an on-line manual, and instructions for obtaining Castep for UK academics (for whom it is free), and EU academics (for whom it is currently E1800).
• Castep at CCPForge, including a bug tracker.
• JISC hosts a Castep email list
• Commerical Castep, from Accelrys.

Castep in TCM

The check2xsf and cellsym utilities are centrally installed.

Further information about Castep itself in TCM can be found on TCM's internal Castep page.