This is the README file for NaCl phonon calculation with DFPT functional of VASP code.

POSCAR in this directory is created as SPOSCAR using the unit cell POSCAR by

% phonopy -d --dim="2 2 2"

This command may be ran in the other directory. Be careful that POSCAR in this direcotry is the supercell, not a unit cell.

To obtain FORCE_CONSTANTS

% phonopy --fc vasprun.xml

Phonon analysis is done such as

% phonopy -c POSCAR-unitcell -p band.conf

Here you can not use POSCAR in this directory. Instead you have to use POSCAR-unitcell that is the original unit cell POSCAR used to create supercell POSCAR at the first step.