Local Molecular Orbitals from a Projection onto Localized Centers

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Molecular Modeling

Background:

• Canonical molecular orbitals often exhibit delocalized characteristics, complicating the interpretation of chemical bonding and electronic properties.
• Developing methods for localizing molecular orbitals is crucial for understanding electronic structure and chemical reactivity.

Purpose of the Study:

• To present a novel localization method for molecular orbitals.
• To investigate the effectiveness of this method for both occupied and virtual molecular orbitals.
• To assess the method's performance across different molecular systems and conformations.

Main Methods:

• Exploiting the locality of eigenfunctions corresponding to the largest eigenvalues of spatially localized functions.
• Projecting canonical orbitals onto eigenvectors derived from localized functions (smooth-step and Hirshfeld partitioning).
• Testing the method on polypeptide molecules in helical and β-sheet conformations.

Main Results:

• The method successfully produces fairly localized occupied molecular orbitals when local functions are centered at molecular bond centers.
• Reasonably well-localized virtual molecular orbitals are achieved with atomic site localization, dependent on the shape of the local functions.
• Adequate localization is demonstrated even for highly delocalized systems, including polypeptides.

Conclusions:

• The presented localization method offers an effective way to obtain localized occupied and virtual molecular orbitals.
• The choice of localization function type and positioning is critical for achieving desired localization characteristics.
• This technique provides valuable insights into the electronic structure of complex molecular systems.