[Phonopy-users] Calculating force sets to get force constants vs calculating force constants directly using DFPT

[Appleton, R. J <ra...@ca...>]

Hello,

I am curious about the similarities and differences of the methods one can use VASP along with phonopy to calculate the force constants. It seems you can either calculate the force sets by doing vasp calculations on each of the displacement poscars and then use the force sets to write a file containing the force constants, or you can calculate the force constants directly using vasp-DFPT on the supercell. I saw that for the Si example there is no difference in the phonon dispersion or density of states using either of these methods. Are they the same or is there slight differences?

Thanks,

Robert Appleton