CASTEP

Both CASTEP 7 and CASTEP 8 are installed and available on ARCHER. We also have serial versions of the program compiled. The different versions can be accessed by loading the correct module.

Licensing and Access

CASTEP is licensed software. Please see the CASTEP web page for details. Users who wish to access the CASTEP package should submit a request via SAFE.

Running CASTEP

To run CASTEP you need to add the correct module:

module add castep

The current default CASTEP module will load CASTEP 8.0.0, but there are modules available for CASTEP 7.0.3, for previous versions of CASTEP 7, and for serial versions of CASTEP.

Once the module has been added the main CASTEP executable is available as castep.mpi. Executables for the tools distributed with CASTEP will also be available.

An example CASTEP job submission script is shown below.

#!/bin/bash --login
#PBS -N castep_job
#PBS -V

# Select 128 nodes (maximum of 3072 cores)
#PBS -l select=128
#PBS -l walltime=03:00:00

# Make sure you change this to your budget code
#PBS -A budget

# Make sure any symbolic links are resolved to absolute path
export PBS_O_WORKDIR=$(readlink -f $PBS_O_WORKDIR)

# Change to the directory that the job was submitted from
cd $PBS_O_WORKDIR

# Load the CASTEP module
module add castep

# This line sets the temporary directory - without it CASTEP will fail
export GFORTRAN_TMPDIR=$PBS_O_WORKDIR

# Change the name of the input file to match your own job
aprun -n 3072 castep.mpi my_job

Compiling

Hints and Tips

When setting the $GFORTRAN_TMPDIR environment variable you must use the absolute /work path rather than a symbolic link to /work from the /home filesystem otherwise your calculation will fail. This is done in the example above by resetting the PBS_O_WORKDIR environment variable using the readlink command.

CASTEP has an option to optimise its run between speed and memory saving. This is controlled either by parameter:

OPT_STRATEGY_BIAS [=-3..3]

or equivalently

OPT_STRATEGY=MEMORY/DEFAULT/SPEED

Normally it should be recommended that users choose OPT_STRATEGY=SPEED/OPT_STRATEGY_BIAS=+3 unless the run attempts to use more memory than available. (Even in that case the first choice should be to increase the number of processors used and distribute the memory if possible.)