Time-Dependent Extension of the Long-Range Corrected Density Functional Based Tight-Binding Method.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Time-dependent density functional theory (TD-DFT) struggles with certain systems, like polyacenes and nucleobases.
• Accurate calculation of electronic excited states is crucial for understanding molecular properties.
• Conventional TD-DFT often fails for large molecules due to artificial low-energy states.

Purpose of the Study:

• To introduce a consistent linear response formulation for long-range corrected density functional based tight-binding (LC-DFTB).
• To address the limitations of conventional TD-DFT for specific challenging systems.
• To provide a computationally efficient method for studying electronic excited states in large molecules.

Main Methods:

• Developed a linear response formulation for LC-DFTB.
• Implemented the new LC-DFTB scheme.
• Tested the method on polyacenes, nucleobases, and molecular dimers with charge transfer excited states.

Main Results:

• The LC-DFTB method shows similar accuracy to range-separated DFT methods for the tested systems.
• It reproduces general trends observed in problematic systems for conventional TD-DFT.
• Achieved these results at a significantly reduced computational cost.

Conclusions:

• LC-DFTB offers a viable and efficient alternative to conventional TD-DFT for electronic excited state calculations.
• The method is particularly promising for large molecules where TD-DFT typically fails.
• This advancement facilitates the study of complex molecular systems and their optical properties.