Hi Archna, you can follow the steps given as https://phonopy.github.io/phonopy/vasp.html

I am not pretty sure about the symmetry option you concerned. Anyway you can have a try. As I am not aware about the material you are studying so difficult to suggest. As you are aware that phonon calculation is quite time consuming process so an excercize of similar crystal symmetry with less number of atom in unit cell can be tested.

Dear Archana Sharma,

1) You can use the default value of ISYM (i.e. just delete the ISYM tag from INCAR).

2) Unfortunately, calculations with IBRION=5,6,7,8 could not be resumed. If there is a problem with the limit of time, I would advise you to calculate phonons using the finite displacement method (There are two approaches to calculate the phonon spectra: first using supercell and IBRION=5,6,7,8; second using POSCARS with displacements generated by phonopy)

Please see https://www.researchgate.net/post/How_to_perform_phonon_dispersion_calculations_using_VASP

(The supercell with 64 atoms is not so large, and the phonon calculation should not take long (but of course it all depends on the number of cores)).

3) The ISMEAR and SIGMA have almost no effect on the calculation speed.

A smaller k-point mesh could help to make your calculations faster, but the too-small k-point mesh can lead to the appearance of imaginary modes in the phonon spectrum.

Hope it will be helpful

Hi,

if you are using phonopy, then you can use DFPT method with SPOSCAR. The details are provided on the link given below.

http://phonopy.github.io/phonopy/vasp-dfpt.html

Also, you can find similar procedure at many other websites for free.

I hope this helps.

Khagesh

hello

In this paper you find how to calculate the phonon in materials

best regards