Orbital Analysis and Excited-State Calculations in an Energy-Based Fragmentation Method

Area of Science:

• Computational Chemistry
• Materials Science
• Photonic Devices

Background:

• Porphyrin-based molecular arrays are key for artificial light-harvesting and photonic devices.
• Investigating large molecular arrays with traditional quantum chemistry methods is computationally prohibitive.

Purpose of the Study:

• Introduce a novel Energy-based fragmentation molecular orbital (EBF-MO) approach.
• Enable theoretical investigation of large molecular systems, including porphyrin arrays.
• Assess the accuracy and applicability of EBF-MO for ground- and excited-state calculations.

Main Methods:

• Developed and implemented the EBF-MO approach into the parallel program JETT.
• Performed benchmark calculations to validate EBF-MO accuracy for systems with transition metals and extended π-conjugation.
• Applied EBF-MO with Density Functional Theory (DFT) and Time-Dependent DFT (TDDFT) to a large porphyrin-based molecular photonic wire.

Main Results:

• EBF-MO accurately calculates orbitals, energies, and properties for large molecular systems.
• TDDFT calculations revealed excited-state characteristics and unidirectional energy transfer in the porphyrin wire.
• Demonstrated the method's suitability for systems with hundreds of atoms and complex electronic structures.

Conclusions:

• The EBF-MO method significantly expands the scope of ab initio and DFT calculations for extended systems.
• This approach facilitates the study of natural and artificial light-harvesting systems and molecular photonic devices.
• Provides a powerful tool for understanding energy transfer mechanisms in complex molecular architectures.