Performance assessment of density-functional methods for study of charge-transfer complexes

Area of Science:

• Computational Chemistry
• Quantum Chemistry

Background:

• Intermolecular pi-pi interactions are crucial in various chemical systems.
• Accurate theoretical prediction of charge-transfer (CT) complex properties is challenging.

Purpose of the Study:

• To evaluate the performance of various density functionals in describing weakly bound intermolecular pi-pi CT complexes.
• To identify functionals that accurately predict excitation energies, intermolecular distances, and binding energies.

Main Methods:

• Application of various density functionals, including mPWPW91, mPW1PW91, PW91PW91, and BH&HLYP.
• Comparison of calculated properties with experimental data for excitation energies, intermolecular distances, and binding energies.

Main Results:

• Most density functionals significantly underestimate experimental excitation energies.
• The BH&HLYP functional shows good agreement with experimental excitation energies.
• PW91PW91 provides accurate intermolecular distances compared to crystal data.
• Hybrid functionals with nonlocal exchange correction yield favorable binding energies.

Conclusions:

• The BH&HLYP functional is recommended for accurate prediction of excitation energies in pi-pi CT complexes.
• Density functional theory performance varies significantly for different properties of these complexes.
• Further development of functionals is needed for precise theoretical descriptions.