Description of intermolecular charge transfer with subsystem density-functional theory

Area of Science:

• Computational Chemistry
• Materials Science
• Quantum Chemistry

Background:

• Accurate modeling of organic semiconductors requires methods that describe intermolecular charge transfer.
• Density-functional theory (DFT) struggles with charge transfer due to fractional charge errors in exchange-correlation (xc) functionals.
• Conventional supermolecular DFT fails for systems like tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ).

Purpose of the Study:

• To develop and validate an enhanced subsystem DFT approach for modeling intermolecular charge transfer.
• To address the fractional charge error inherent in approximate xc functionals.
• To enable accurate and efficient simulations of organic semiconductor materials.

Main Methods:

• Extension of subsystem DFT to handle subsystems with fractional electron numbers.
• Enforcement of correct energy dependence on fractional charge for each subsystem.
• Investigation of charge transfer in a TTF-TCNQ complex under an external electric field.

Main Results:

• The extended subsystem DFT successfully overcomes the fractional charge error.
• Accurate description of intermolecular charge transfer in the TTF-TCNQ model system is achieved.
• The method demonstrates potential for accurate modeling of larger molecular aggregates.

Conclusions:

• The presented subsystem DFT framework accurately captures intermolecular charge transfer.
• This approach provides a pathway for efficient and reliable modeling of organic semiconductors.
• The generalization of this method is crucial for advancing materials science simulations.