Comprehensive Analysis of the Neglect of Diatomic Differential Overlap Approximation

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Modern semiempirical molecular orbital models rely on the neglect of diatomic differential overlap (NDDO) approximation.
• A deep understanding of NDDO is crucial for explaining the efficacy of these models and for future advancements.

Purpose of the Study:

• To analyze the NDDO approximation by comparing electron-electron repulsion integrals (ERIs) in different bases.
• To investigate methods for correcting NDDO-induced errors.
• To propose a strategy for direct error correction within the Fock operator's two-electron matrices.

Main Methods:

• Comparison of ERIs in symmetrically and locally orthogonalized bases for various molecules and basis sets.
• Analysis of error propagation in Hartree-Fock and second-order Møller-Plesset perturbation theory energies.
• Examination of error correction strategies for NDDO approximation.

Main Results:

• Errors in Hartree-Fock and Møller-Plesset energies scale approximately linearly with the number of basis functions.
• The study identifies and analyzes sources of error stemming from the NDDO approximation.
• A novel strategy for direct correction of NDDO errors is proposed.

Conclusions:

• The NDDO approximation's impact on computational accuracy is quantifiable and linked to basis set size.
• The proposed direct correction strategy offers a pathway to enhance the reliability of semiempirical molecular orbital calculations.
• Further development of NDDO-based methods can benefit from understanding and mitigating approximation-induced errors.