Why Computational Photochemistry Is Challenging and Will Probably Remain So: A Quantum Chemist's Perspective

Area of Science:

• Computational Chemistry
• Theoretical Chemistry
• Photochemistry

Background:

• Molecular photochemistry involves electronically excited states, making theoretical descriptions complex.
• Accurate computation of multiple electronic states and their potential energy surfaces (PES) is crucial.

Purpose of the Study:

• To discuss the challenges in computational photochemistry from an electronic structure theory perspective.
• To highlight the trade-off between accuracy and computational cost for larger molecules.

Main Methods:

• Electronic structure theory calculations.
• Analysis of potential energy surfaces (PES) for excited states.

Main Results:

• Theoretical description of photochemistry is fundamentally more complex than ground-state chemistry.
• Accuracy requirements increase with molecular size, challenging common electronic structure methods.
• Excitation energies decrease and more states fall within error margins for larger systems.

Conclusions:

• Computational photochemistry faces significant size limitations due to accuracy and computational cost.
• A compromise between accuracy and effort is inherent in computational photochemistry.
• Accurate theoretical investigations transition to estimations for larger molecular systems.