phelel_params.hdf5
The phelel_params.hdf5 file is used to calculate electron-phonon interactions via ELPH_RUN = True.
It contains information related to the interatomic force constants and the derivative of the Kohn-Sham potential.
To generate the phelel_params.hdf5 file, you can either use the VASP internal driver via ELPH_POT_GENERATE = True or use VASP in combination with phelel.