In practice, we perform three additional single-point calculations for each of the selected MD snapshots. In these calculations, a finite periodic electric field E, which is computed using the Berry phase approach and has a field strength of 0.005 a.u., is applied along the x, y or z direction, i.e., we apply the fields (E, 0, 0), (0, E, 0) or (0, 0, E). After convergence of the electronic structure, we compute the electric dipole moment µ µ µ k , where k indicates the direction in which the field has been applied. The induced dipole moment is then calculated via forward finite differences as: