My Community

Dear VASP developers and users,

I encounter a problem on the post processing of phonon calculation. I have finished a finite difference based phonon frequency calculation by using VASP (i.e., IBRION=6 and NFREE=2. NOT by using phonopy!), obtaining the frequencies at the Gamma point as well as a series of output files such as OUTCAR and DYNMAT. Now I want to change the masses of several atoms, and obtain the corresponding phonon frequencies. I am wondering if there are any programs or software could derive the phonon frequencies based on the output files (such as OUTCAR or DYNMAT) directly, without re-performing the phonon calculation with different atomic masses?

Sincerely
Hua Tian

Yes, this should be possible.

If you are familiar with phonopy you can use it to read in the hessian matrix produced by VASP using this procedure:
http://phonopy.github.io/phonopy/vasp-dfpt.html

Note that this page seems to indicate that this is only possible when using the DFPT driver in VASP ( IBRION=7 or 8 ) but from my testing, it also works with (IBRION=5 or 6) since VASP produces the same entries in the vasprun.xml file.

Dear Dr. Miranda,

Thank you very much for your guidance! Indeed, I am familiar with phonopy, and this procedure works very well.

Sincerely，
Tian Hua

henrique_miranda wrote: ↑Wed Jul 27, 2022 9:09 am Yes, this should be possible.

If you are familiar with phonopy you can use it to read in the hessian matrix produced by VASP using this procedure:
http://phonopy.github.io/phonopy/vasp-dfpt.html

Note that this page seems to indicate that this is only possible when using the DFPT driver in VASP ( IBRION=7 or 8 ) but from my testing, it also works with (IBRION=5 or 6) since VASP produces the same entries in the vasprun.xml file.