Excited states using the simplified Tamm-Dancoff-Approach for range-separated hybrid density functionals: development...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Accurate computation of electronic excitation spectra is crucial for understanding molecular properties.
• Existing methods struggle with large molecular systems and specific types of electronic transitions.
• Range-separated hybrid (RSH) density functionals offer improved accuracy for certain electronic properties.

Purpose of the Study:

• To extend the screened Tamm-Dancoff Approximation (sTDA) methodology to range-separated hybrid (RSH) functionals.
• To enable accurate computation of excitation spectra for large molecular systems.
• To assess the performance of the new sTDA-RSH method against theoretical benchmarks.

Main Methods:

• Empirical parameters for screened two-electron interaction were fitted for common RSH functionals (e.g., CAM-B3LYP, ωB97 family).
• Method was validated using theoretical SCS-CC2 reference vertical excitation energies.
• Cross-validation performed on charge transfer states and valence transitions in various molecular systems.

Main Results:

• The sTDA-RSH method achieved small deviations (0.2-0.4 eV) from reference data.
• CAM-B3LYP and ωB97X-D3 functionals showed the best performance.
• Successfully computed 11,000+ excited states for a 330-atom system, demonstrating scalability.

Conclusions:

• The extended sTDA-RSH methodology provides accurate excitation spectra for large molecules.
• This approach offers superior results compared to global hybrid functionals for excited states.
• Opens new avenues for computational studies in materials science and biomolecular systems.