Improving Excited-State Potential Energy Surfaces via Optimal Orbital Shapes

Area of Science:

• Quantum chemistry
• Computational chemistry
• Theoretical chemistry

Background:

• Excited-state potential energy surfaces (PES) are crucial for understanding photochemical reactions.
• Traditional methods for excited-state PES calculations often involve high computational costs or approximations.
• Qualitative failures in predicting excited-state PES can limit the accuracy of reaction mechanism studies.

Purpose of the Study:

• To demonstrate a cost-effective method for improving excited-state potential energy surface predictions.
• To show that using state-specific orbitals can remedy qualitative failures in PES calculations.
• To avoid the need for expensive dynamic correlation methods and wave function response calculations.

Main Methods:

• Employing optimal molecular orbitals tailored for each individual excited state.
• Utilizing a single-state approach for excited-state geometry relaxation.
• Applying the method to systems including double bond dissociation, amino hydrogen dissociation, and intramolecular charge transfer.

Main Results:

• Qualitative improvements in excited-state PES predictions were achieved without additional computational cost.
• The state-specific orbital approach eliminated the need for state-averaging or dynamic weighting choices.
• The method obviated the requirement for expensive wave function response calculations for geometry relaxation.

Conclusions:

• Optimal single-state molecular orbitals provide a computationally inexpensive yet accurate alternative for excited-state PES calculations.
• This approach offers significant benefits for various features of excited-state PES, particularly away from conical intersections.
• The findings suggest a paradigm shift towards more efficient and accurate computational studies of excited-state dynamics.