Method for Calculating Excited Electronic States Using Density Functionals and Direct Orbital Optimization with Real...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Accurate calculation of excited electronic states is crucial for understanding photochemistry and photophysics.
• Traditional methods often struggle with convergence for complex systems and specific excitation types.

Purpose of the Study:

• To present a direct orbital optimization method for calculating excited electronic states.
• To enable accurate computation of atomic forces in excited states.
• To apply the method to various challenging chemical systems.

Main Methods:

• A variational direct orbital optimization approach using real space grids or plane-wave basis sets.
• Implementation involves nested loops for Kohn-Sham (KS) and orbital-density-dependent (ODD) functionals.
• Combines with the maximum overlap method for improved convergence.

Main Results:

• Demonstrates convergence in challenging cases where conventional methods fail.
• Successfully calculates charge-transfer excitations, excitations to degenerate orbitals, and metal-centered excited states.
• Analyzes the impact of self-interaction correction on excited states.

Conclusions:

• The developed method offers a robust and accurate approach for excited state calculations.
• It provides reliable atomic forces, crucial for dynamics simulations.
• Applicable to a wide range of systems, including photosensitizers and molecules with self-interaction errors.