Wavefunction frozen-density embedding with one-dimensional periodicity: Electronic polarization effects from local perturbations

We report an approach to treat polarization effects in a one-dimensional (1D) environment using frozen-density embedding (FDE), suitable to compute response to electron loss or attachment as occurring in organic semiconductors during charge migration. The present work provides two key developments: (a) Local perturbations are computed avoiding an infinite repetition thereof and (b) a first-order equation-of-motion ansatz is used to compute polarization effects due to electron loss and attachment, ensuring an efficient calculation by avoiding open-shell calculations. In a first step, an unperturbed 1D molecular chain is equilibrated using FDE by translation of the center molecule. In a subsequent second step, long-range contributions are frozen and a local perturbation is introduced in the center subsystem. Freeze–thaw iterations are used to relax the electronic wavefunction of both the center subsystem and subsystems in an active region around the center subsystem, avoiding the need to translate the perturbation. The proposed scheme proves to be very efficient and allows for the calculation of charged tetraazaperopyrenes in 1D chains. ... mehrDue to its efficiency, the new method is capable of providing wavefunction-based reference data relevant for electronic couplings in complex environments.