phonopy/example/Cr/README.md

Cr with collinear magnetic moments

This is an example to calculate phonon with magnetic symmetry by collinear magnetic moments. Supercells with displacements can be created by running following command:

% phonopy -d --dim 2 2 2 --pa "-1/2 1/2 1/2 1/2 -1/2 1/2 1/2 1/2 -1/2" --magmom "1 -1" -c POSCAR-unitcell

--magmom option has to be specified to correctly recognize the magnetic symmetry. --pa option is added because this system has the type-4 magnetic space group and this choice of the unit cell. Currently, --pa auto cannot be used for magnetic space groups.

A file named MAGMOM is created together with supercell POSCARs. In the MAGMOM file, a line of MAGMOM is written, which can be used in VASP INCAR. Running force calculation (350 eV, 0.1 eV smearing, 20x20x20 k-points for unit cell), we obtain vasprun.xml. With this, FORCE_SETS is created by

% phonopy -f vasprun.xml.xz

Then phonon calculation is achieved by, e.g.,

% phonopy-load --band "1/2 -1/2 1/2 0 0 0 1/4 1/4 1/4" -p