Running CASTEP

CASTEP has two main input files, called the cell file and the param file. The cell file defines the structure of the material (or molecule) you wish to study, and the param file defines the kind of simulation CASTEP should perform.

The cell and param files should be named using the same prefix, which CASTEP calls the "seedname", with the extensions .cell and .param, respectively. For example, for a calculation called mytest, you need the input files

mytest.cell
mytest.param

and the calculation is run with the command

castep mytest

The main CASTEP output file will be names using the same seedname and the .castep extension, i.e. in the above example it would be called mytest.castep. If this file already exists, CASTEP will append its output to it.

When CASTEP completes successfully, it writes additional files such as the .bib file, which contains references to key papers for the theory and methods CASTEP used.

If CASTEP encounters a serious problem, it will stop and write an error message to a .err file. If you are using the parallel version of CASTEP on many cores, you may see error files from each of these cores. They are named using the same seedname, but with the numeric process ID added, e.g. if CASTEP is run on 2 cores and a serious problem occurs, you might see the files

mytest.0001.err
mytest.0002.err

These files contain useful information about what went wrong, so it is always worth looking at them. See the Troubleshooting Guide for details of how to find and fix common problems.