NaCl phonon dispersions with non-analytical correction

CRYSTAL output file is crystal.o. This is the default file name
for the CRYSTAL interface, so, the -c crystal.o parameter is not needed

CRYSTAL output file crystal.o includes the Born effective
charges and the dielectric tensor
(from FREQCALC-INTENS-INTCPHF, see the input in the beginning of crystal.o)

1) Create displaced supercells:
   phonopy --crystal --dim="4 4 4" -d
   Complete CRYSTAL inputs can be prepared manually
   or with the help of a template (see TEMPLATE)

2) Create BORN file for non-analytical correction:
   phonopy-crystal-born > BORN

3) Run the supercell inputs with CRYSTAL
   Here supercell-001.o and supercell-002.o have been pre-calculated.

4) Collect forces:
   phonopy --crystal -f supercell-*o

5) Calculate phonon dispersion data into band.yaml and save band.pdf
   Take the non-analytical correction into account using --nac (see BORN file):
   phonopy --crystal --dim="4 4 4" -p -s --nac band.conf

   Plot the phonon dispersion in cm^{-1} units:
   (factor = CrystalToTHz * THzToCm = 15.633302 * 33.356410)
   phonopy --crystal --dim="4 4 4" -p -s --nac --factor=521.47083 band.conf

   Create a formatted plot (here band.yaml is in cm^{-1) units):
   phonopy-bandplot --fmin=0 --line --ylabel="Frequency (cm\$^{-1}\$)" --band-labels="`grep BAND_LABELS band.conf | cut -d= -f2-`" -o dispersion.pdf
