Simplified Tuning of Long-Range Corrected Time-Dependent Density Functional Theory.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Range-separated hybrid functionals enhance charge-transfer excitation descriptions in time-dependent density functional theory (TD-DFT).
• Optimal tuning via the ionization energy (IE) criterion (ε_HOMO = -IE) improves TD-DFT accuracy but is computationally demanding and system-specific.

Purpose of the Study:

• To introduce and evaluate global density-dependent (GDD) tuning as an automated, efficient alternative to IE tuning for TD-DFT.
• To compare the performance of GDD and IE tuning for describing valence and charge-transfer excitations.

Main Methods:

• Implementation of global density-dependent (GDD) tuning for range-separated hybrid functionals.
• Calculation of excitation energies using TD-DFT with both GDD and IE tuning.
• Assessment of computational efficiency and applicability to various system sizes.

Main Results:

• GDD and IE tuning produce comparable excitation energies for small molecules, including charge-transfer excitations.
• GDD tuning demonstrates superior efficiency and scalability for larger systems.
• GDD tuning functions as a robust, automated 'black-box' method.

Conclusions:

• GDD tuning provides a practical and efficient alternative to IE tuning for TD-DFT applications.
• This automated approach simplifies the accurate calculation of excitation energies, particularly for large and extended systems.