Link atom bond length effect in ONIOM excited state calculations

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• The N-layer integrated molecular orbital molecular mechanics (ONIOM) hybrid method is a powerful tool for approximating electronic transition energies.
• Previous work demonstrated ONIOM's accuracy in approximating high-level electronic transition energies, such as those from equation of motion coupled cluster singles and doubles (EOM-CCSD) calculations.
• Understanding the influence of system definition parameters is crucial for reliable ONIOM applications.

Purpose of the Study:

• To investigate the effect of link atom bond length on electronic transition energy calculations using the ONIOM hybrid method.
• To determine if guidelines for ONIOM ground state calculations are applicable to excited state calculations.
• To propose new guidelines for optimizing excited state ONIOM calculations and assessing model system effectiveness.

Main Methods:

• Utilized the ONIOM hybrid method for electronic transition energy calculations.
• Performed calculations by varying the link atom bond length within the ONIOM framework.
• Compared results with high-level theoretical methods like EOM-CCSD.

Main Results:

• The choice of link atom bond length has a minimal effect on the ONIOM electronic transition energy when an appropriate model system is employed.
• Established that guidelines for ONIOM ground state calculations can be effectively applied to excited state calculations.
• Identified the robustness of ONIOM for excited state energy approximations, irrespective of minor variations in link atom bond length.

Conclusions:

• The ONIOM method provides reliable electronic transition energies for excited states, with link atom bond length being a non-critical parameter for well-defined model systems.
• The study validates the transferability of ONIOM parameterization guidelines from ground state to excited state calculations.
• Further guidelines are suggested for enhancing the reliability and interpretability of excited state ONIOM calculations.