[Phonopy-users] [help] Query for translation imaginary modes taken into account by phonopy

[BHATTI A. <Asi...@ls...>]

Hello,

I have a disordered structure and want to know the stability and thermal properties of the structure and this can be obtained through vibrational analysis.

I optimized my structure with VASP until the forces were E=-1E-4. I used DFPT to obtain the Hessian matrix (for this aproach we don't need to build larger supercells). When I checked the OUTCAR there were three imaginary modes (the last three can be ignored because they are translationary modes). Now when I generate the FORCE_CONSTANTS using phonopy it takes into account these modes which can be seen in the DOS and BAND structure.

Should I remove these imaginary translationary modes before submitting them to Phonopy? vasprun.xml doesn't display any imaginary modes only OUTCAR does.

Is this the right procedure? The acoustic soft modes are flat near the Gamma point.

NB: I am attaching a file so you can see where the problem is.

Regards,
Asif