Long-range dynamical matrix correction works for Quantum EPSRESSO force constants, but not for Phonopy force constants

[BogdanRajkov]

The long-range correction method implemented in Phoebe follows the implementation in QE. It is assumed that the force constants (IFCs) are calculated in q-space and then Fourier transformed to real space, as described by Gonze and Lee. IFCs can also be calculated directly in real-space with finite-difference methods, as is done in JDFTx and Phonopy, and detailed in the paper by Wang et al.. In both cases, IFCs are corrected for long-range dipole-dipole interactions. However, the correction is different in the two cases, and currently only the former is implemented in Phoebe. QE includes a subroutine for correcting finite-difference methods as well, and this subroutine needs to be transferred to Phoebe.