Hi,
I am able to calculate the phonon band structure, using VASP and harmonic force constants generated by Phonopy. But I would like to calculate this at a given temperature, for example 300K, using anharmonic force constants. I think I may need to use phonopy-qha or SCAILD, but am unsure how to do so.
The method I am currently using:
phonopy -d --dim="2 2 2" -c POSCAR-unitcell
cp SPOSCAR POSCAR
Run VASP using: PREC = Accurate ENCUT = 500 IBRION = 8 EDIFF = 1.0e-08 IALGO = 38 ISMEAR = 0; SIGMA = 0.1 LREAL = .FALSE. ADDGRID = .TRUE. LWAVE = .FALSE. LCHARG = .FALSE.
phonopy --fc vasprun.xml
phonopy -p --dim="2 2 2" -c POSCAR-unitcell band.conf
sumo-phonon-bandplot --poscar POSCAR-unitcell --dim 2 2 2 -f FORCE_CONSTANTS --dos --width 8 --kpoints "0 0 0, 0 0.5 0, 0 0.5 0.5, 0 0 0.5, 0 0 0" --labels "$\Gamma$, F, Q, Z, $\Gamma$"
Dear Cameron C. L. Underwood
If you use Phonopy, QHA is the simplest approach that helps you to calculate the T-dependence of phonons. For this however, you need at least five volume points, meaning that you must run both VASP and Phonopy for several lattice constants. For more info, please refer to the Phonopy manual: Article Temperature-dependent phonon spectrum of transition metal di...
I also recommend you to have a look at this paper (Article Temperature dependence of phonons in FeGe 2
), in which the authors use both QHA and so-called stochastically initialized temperature-dependent effective potential method to study the effect of temperature on phonons.
Dear Cameron C. L. Underwood,
Unfortunately, phonopy can not calculate phonon band structure at finite temperature (only at 0K). Phonopy-qha is used only for quasiharmonic approximation (i.e. phonopy-qha uses phonons at 0K to calculate thermal properties). To calculate phonon band structure (phonon dispersion curves) at the finite temperature you need programs like "phono3py" or "alamode".
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