The DFPT polarizabilities are obtained for the whole supercell, while individual contributions are not accessible, unless modifications are made to the DFPT code. An important advantage compared to the induced dipole method introduced in Section 2.3.1 is that the polarizabilities are directly obtained after a single linear-response calculation, requiring no manual adjustments of field strengths or postprocessing steps. We note that also the DFPT polarizabilities are uniquely defined due to multiplication with the inversion of S nm in Equation ( ), canceling the phase indeterminancy.