Charge-Transfer Excitation within a Hybrid-(G)KS Framework through Cartesian Grid DFT

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Organic molecules with charge-transfer (CT) excited states are fundamental to electron transfer processes and molecular conductance.
• Accurate characterization of these electronic states is essential for understanding and designing novel molecular systems.

Purpose of the Study:

• To present a straightforward and accurate computational technique for characterizing CT excited states.
• To evaluate the performance of this method using various density functionals and challenging molecular systems.

Main Methods:

• Utilized Becke's excitation theorem to relate singlet-triplet energy splitting to a two-electron integral.
• Developed a novel numerical strategy for evaluating this integral on a Cartesian grid.
• Assessed the method's accuracy with BLYP, B3LYP, and LC-BLYP functionals on CT complexes and challenging molecules.

Main Results:

• The numerical strategy demonstrated consistency with the original Becke's excitation theorem.
• The method accurately described the asymptotic limit of CT excitation energies.
• The hybrid B3LYP functional showed particular accuracy in describing CT excitation energies.

Conclusions:

• The proposed simple technique provides an accurate picture of CT excited states in organic molecules.
• This method is feasible and effective for studying complex molecular systems relevant to electron transfer and molecular electronics.