Site-Specific Ionization Potentials and Electron Affinities in Large Molecular Systems at Coupled Cluster Level

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Accurately predicting ionization potentials (IPs) and electron affinities (EAs) is crucial for understanding chemical reactivity and material properties.
• Environmental effects significantly influence molecular electronic properties, posing a challenge for theoretical calculations.
• Existing methods often struggle to efficiently incorporate nonlocal environmental contributions.

Purpose of the Study:

• To develop a many-body expansion method for calculating IPs and EAs.
• To incorporate nonlocal environmental effects using equation-of-motion coupled-cluster (EOM-CC) theory.
• To assess the method's accuracy for diverse chemical systems.

Main Methods:

• A many-body expansion approach was combined with the fragment molecular orbital (FMO) method.
• Equation-of-motion coupled-cluster (EOM-CC) calculations were used to determine pair and triple corrections.
• The method was applied to carboxylic acids, alkyl cations, ubiquitin protein, and a graphene nanoribbon.

Main Results:

• The developed method successfully calculated site-specific IPs and EAs.
• Pair and triple corrections effectively accounted for environmental influences.
• Significant environmental effects on IPs and EAs were observed for all studied systems.

Conclusions:

• The combined FMO-EOM-CC method provides an accurate and efficient way to study environmental effects on IPs and EAs.
• This approach is applicable to a wide range of systems, from small molecules to large biomolecules and materials.
• The findings highlight the importance of considering the molecular environment in electronic property predictions.