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

Abstract

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 semi conductors 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 (EOM) 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 renders to be very efficient and allows for the calculation charged tetraazaperopyrenes in 1D chains. Due to the efficiency, the new method can provide wavefunction-based reference data relevant for electronic couplings in complex environments.

Subsystem density‐functional theory (update)

“…This has been applied to calculate electron attachment and ionization as well as excitation energies in one-dimensional stacks of organic semiconductors. 194,195 3D quasi-periodic calculations have been achieved in terms of so-called relax-and-copy-cycles for molecular crystals. 35 During the relax step in these cycles, the orbitals of the molecules in an inner unit cell are determined, embedded in a guess electron density for the molecules in surrounding unit cells.…”

“…To this end, an embedding potential is generated by periodically repeating the electron density of the active molecular subsystem, which is in turn used to embed this active subsystem into the environment of its own periodic images. This has been applied to calculate electron attachment and ionization as well as excitation energies in one‐dimensional stacks of organic semiconductors 194,195 …”

Subsystem Density-Functional Theory (Update)

“…To this end, an embedding potential is generated by periodically repeating the electron density of the active molecular subsystem, which is in turn used to embed this active subsystem into the environment of its own periodic images. This has been applied to calculate electron attachment and ionization as well as excitation energies in one-dimensional stacks of organic semiconductors [194,195]. 3D quasi-periodic calculations have been achieved in terms of so-called relax-copy-cycles for molecular crystals [35].…”

Subsystem Density-Functional Theory (Update)

“…To this end, an embedding potential is generated by periodically repeating the electron density of the active molecular subsystem, which is in turn used to embed this active subsystem into the environment of its own periodic images. This has been applied to calculate electron attachment and ionization as well as excitation energies in one-dimensional stacks of organic semiconductors [192,193].…”