Questaal & phonopy calculation#
This is a tutorial for the interface between phonopy and Questaal https://www.questaal.org/.
The interface uses the site files. Such files have only a small amount of information within them relating to the calculation. Extention to support ctrl files is planned.
How to run#
The following is a walkthrough for a phonopy calculation with LM:
Setup an
lmf
calculation with external site file instead of asite
section in the ctrl file. Both relative and cartesian coordinates are supported. Remember to setforces=1
in sectionham
of the ctrl file.Read the LM site file and create supercells with a command of the form,
phonopy --qlm -d --dim='2 2 2' -c site.lm
In this example, 2x2x2 supercells are created.
supercell.lm
andsupercell-{id}.lm
correspond to the perfect supercell and supercells with displacements, respectively. These supercell files are LM site files ready to be used inctrl.lm
. The originalalat
present in site.lm is preserved. A file namedphonopy_disp.yaml
is also created in the current directory. This file contains information pertaining to displacements.Next, run the calculations for the generated displacements and be sure to use the
--wforce=force
flag. This will write a file containing forces. Phonopy will require this file to be read in the next step.Create
FORCE_SETS
by:phonopy --qlm -f supercell-001/force.lm supercell-002/force.lm ...
To run this command,
phonopy_disp.yaml
has to be located in the current directory because the atomic displacements are written into theFORCE_SETS
file.Run post-process of phonopy with the LM site file for the unit cell used in the first step
phonopy --qlm -c site.lm -p band.conf
or
phonopy --qlm -c site.lm --dim="2 2 2" [other-OPTIONS] [setting-file]