Hi Alex,
I have followed your suggestion to use a very tight relaxed structure and also a tight energy convergence for the DFPT. I also checked OSZICAR to see if every step is converged. But the problem is not solved.
It seems that this forum doesn’t allow to upload any files except pictures. I have to upload the INCAR/KPOINTS/POSCAR/OSZICAR and OUTCAR of my DFPT calculation to the original post on Github.
I only used VASP DFPT funtion for several times, and this is quite new and confusing to my. I’m really appreciated that you can help me solve this problem.
Thanks,
Zhi