A computationally efficient and reliable bond order measure

Area of Science:

• Computational chemistry
• Quantum chemistry
• Chemical bonding theory

Background:

• Bond order indexes bridge quantum mechanics and chemical intuition.
• Natural bond order (NBO) index is reliable but computationally intensive for large systems.
• NBO calculations scale poorly with basis set size and system delocalization.

Purpose of the Study:

• Introduce a new, computationally efficient bond order index.
• Develop a reliable alternative to the NBO index for large molecular systems.
• Assess the accuracy and applicability of the new index.

Main Methods:

• Developed the first order perturbation theory bond order (fopBO) index.
• Utilized natural bond orbital (NBO) analysis tools as a foundation.
• Performed test calculations on various molecular systems.

Main Results:

• The fopBO index demonstrates reliability comparable to the NBO index.
• fopBO shows weak sensitivity to common basis set variations.
• fopBO is computationally feasible for large, biologically relevant molecules.

Conclusions:

• The fopBO index provides a reliable and computationally tractable method for bond order analysis.
• fopBO overcomes the scalability limitations of NBO for large systems.
• This new index facilitates the study of complex chemical systems in biology and beyond.