Phonon Calculations with Phonopy

Install Phonopy

How to use Phonopy

1) Optimize your unit cell geometry using VASP

2) Create your supercells using Phonopy

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

This creates 2x2x2 supercells. SPOSCAR is the perfect supercell, and symmetry-nonequivalent atomic distortions in POSCAR-001, POSCAR-002, etc.

3) Create subfolders for the distortions (POSCAR-001 and so on) and run force calculations on the supercells. Note, do not relax the structures. Use IBRION = -1 and ISIF = default. These calculations are very memory intensive so choose your submission queue wisely

3) Once you have calculated the forces create FORCE_SETS

phonopy -f <folder_001>/vasprun.xml <folder_002>/vasprun.xml

Post processing

1) Create 'mesh.conf'. See example below:

ATOM_NAME = Si O

DIM = 2 2 2

MP = 8 8 8

MP is the setting for uniform meshes in each direction

2) To create density of states:

phonopy -p mesh.conf

3) To calculate thermal properties:

phonopy -t mesh.conf

4) To plot thermal properties:

phonopy -t -p mesh.conf

5) To create band structure create 'band.conf':

ATOM_NAME = Si O

DIM =  2 2 3

BAND = 0.5 0.5 0.5  0.0 0.0 0.0  0.5 0.5 0.0  0.0 0.5 0.0

where BAND indicates the band structure path (reciprocal lattice vectors)

Print the band structure with:

phonopy -p band.conf

6) If wanted, the tag '-s' prints the results to a PDF. For more functions of Phonopy checkout their tutorials page