Semiempirical Quantum-Chemical Orthogonalization-Corrected Methods: Benchmarks of Electronically Excited States

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Semiempirical OMx methods are effective for ground-state calculations.
• These methods can be extended to excited states using multireference configuration interaction (MRCI).

Purpose of the Study:

• To comprehensively evaluate the performance of OMx/MRCI methods for electronically excited states.
• To benchmark against other computational methods like TDDFT/B3LYP, CC2, MRCISD, and CASPT2.

Main Methods:

• Application of OMx/MRCI methods to compute excited-state properties.
• Benchmarking included vertical excitation energies, geometries, conical intersections, and transition energies.
• Evaluated 520 molecular structures and 412 excited states.

Main Results:

• OMx/MRCI methods demonstrate reasonable performance for various excited-state properties.
• Identified specific shortcomings when compared to ab initio methods.
• Analysis of geometry changes between ground and excited states was performed.

Conclusions:

• OMx/MRCI methods offer a viable approach for excited-state calculations.
• Further refinement is necessary to match the accuracy of first-principles methods.
• The study provides valuable data for future method development in computational chemistry.