CASTEP & phonopy calculation

Examples to use phonopy with CASTEP as the force calculator are found at example/NaCl-castep and example/Cr-castep.

The followings are the copies of README contents in these example directories.

These are contriubted by @ladyteam.

NaCl-castep

This is step-by-step example how to calculate phonon dispertion with CASTEP.

1. Generate supercell based on structrural parameters given in unitcell.cell file by running:

   % phonopy -d --dim="2 2 2" --castep -c unitcell.cell
   

   In this example file unitcell.cell contains initial spin values in positions_frac BLOCK. As well as the value of the U parameter in LDA+U approximation.

2. Use make_displ_dirs.sh bash script to make directories with input files needed to calculate FORCES for supercells.

   % make_displ_dirs.sh supercell.param tail.cell
   

   Please note file supercell.param is the standart CASTEP file with paremeters (convergence criteria, Ecut, functional name etc.). The file with name tail.cell contains k-mesh description, U parameter value, symmetry operation E, and name of pseudopotential.

3. Run CASTEP calculation in displ-001 directory

4. Generate FORCE_SETS file by running:

   % phonopy --castep -f displ-001/supercell.castep displ-002/supercell.castep
   

5. Finally plot phonon bandstructure by running the following command:

   % phonopy --castep -c unitcell.cell -p band.conf
   

Cr-castep

This is step-by-step example how to calculate phonon dispertion with CASTEP. Spin-polarization example.

1. Generate supercell based on structrural parameters given in unitcell.cell file by running:

   % phonopy -d --dim="2 2 2" --castep -c unitcell.cell
   

   In this example file unitcell.cell contains initial spin values in positions_frac BLOCK. As well as the value of the U parameter in LDA+U approximation.

2. Use make_displ_dirs.sh bash script to make directories with input files needed to calculate FORCES for supercells.

   % make_displ_dirs.sh supercell.param tail.cell
   

   Please note file supercell.param is the standart CASTEP file with paremeters (convergence criteria, Ecut, functional name etc.). The file with name tail.cell contains k-mesh description, U parameter value, symmetry operation E, and name of pseudopotential.

3. Run CASTEP calculation in displ-001 directory

4. Generate FORCE_SETS file by running:

   % phonopy --castep -f displ-001/supercell.castep
   

5. Finally plot phonon bandstructure by running the following command:

   % phonopy --dim="2 2 2" --pa="-1/2 1/2 1/2 1/2 -1/2 1/2 1/2 1/2 -1/2" --castep -c unitcell.cell --band="1/2 -1/2 1/2 0 0 0 1/4 1/4 1/4" -p