On the applicability of fragmentation methods to conjugated pi systems within density functional framework

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Linear scaling methods (LSMs) enable accurate ab initio treatment of large molecular systems.
• Existing LSMs are effective for covalently bonded and weakly interacting systems.
• Limited research exists on applying LSMs to highly conjugated, especially 2D, systems.

Purpose of the Study:

• To investigate the applicability of the molecular tailoring approach (MTA), a type of LSM, to pi-conjugated systems within density functional theory.
• To evaluate MTA's accuracy and efficiency for 1D and 2D pi-conjugated molecules.
• To explore MTA's potential for large-scale 2D and 3D conjugated systems.

Main Methods:

• Application of the molecular tailoring approach (MTA) within density functional theory.
• Testing MTA on 1D pi-conjugated molecules and comparing energies with actual values.
• Extending MTA to small/medium 2D pi-conjugated systems using a systematic algorithm.
• Performing geometry optimization for 2D systems using MTA and comparing results with actual calculations.

Main Results:

• For 1D pi-conjugated molecules, MTA energy differences were less than 1 mhartree, with reduced computation time and hardware requirements.
• For 2D pi-conjugated systems, MTA energies had errors of a few millihartrees, but gradients matched actual counterparts well.
• Geometry optimization using MTA yielded results in good agreement with actual calculations, with single-point energies matching within 1 mhartree.

Conclusions:

• MTA is a viable and efficient method for treating 1D pi-conjugated systems with high accuracy.
• MTA shows promise for the geometry optimization of 2D pi-conjugated systems, despite minor energy discrepancies.
• The findings suggest MTA's potential applicability to large-scale 2D and 3D pi-conjugated systems, offering significant computational advantages.