SiO2 high pressure phase of Stishovite. The unit cell was relaxed using VASP with 'PSTRESS = 400' in INCAR. In BORN file, Born effective charges of atom 1 and 3 are written. Dielectric and Born effetive charge tensors were calculated using VASP with 'LEPSILON = .TRUE.' in INCAR. Band structure with LO-TO splitting is plotted by

% phonopy -p --nac band.conf

Small imaginary acoustic mode may appear due to the shortage of supercell size. FORCE_SETS file can be re-created by

% phonopy -f vasprun.xml-00{1..3}

An animation file for the v_sim viewer is created by

% phonopy anime.conf

INCAR file in this directory gives an example of setting for calculating Born effective charge and dielectric constant.
