Semiempirical Molecular Orbital Models based on the Neglect of Diatomic Differential Overlap Approximation

TL;DR

This paper reviews semiempirical molecular orbital models based on the NDDO approximation, analyzing their formalism, electron correlation treatment, and limitations through benchmark studies and sensitivity analysis.

Contribution

It provides a comprehensive, self-contained review of NDDO-SEMO models, including recent developments, correlation approaches, and systematic limitations analysis.

Findings

Benchmark studies reveal strengths and weaknesses of NDDO-SEMO models.

Sensitivity analysis identifies key parameters affecting model accuracy.

Systematic limitations are characterized by analogy to DFT methods.

Abstract

Semiempirical molecular orbital (SEMO) models based on the neglect of diatomic differential overlap (NDDO) approximation efficiently solve the self-consistent field equations by rather drastic approximations. The computational efficiency comes at the cost of an error in the electron-electron repulsion integrals. The error may be compensated by the introduction of parametric expressions to evaluate the electron-electron repulsion integrals, the one-electron integrals, and the core-core repulsion. We review the resulting formalisms of popular NDDO-SEMO models (such as the MNDO(/d), AM1, PMx, and OMx models) in a concise and self-contained manner. We discuss the approaches to implicitly and explicitly describe electron correlation effects within NDDO-SEMO models and we dissect strengths and weaknesses of the different approaches in a detailed analysis. For this purpose, we consider the results of recent benchmark studies. Furthermore, we apply bootstrapping to perform a sensitivity analysis for a selection of parameters in the MNDO model. We also identify systematic limitations of NDDO-SEMO models by drawing on an analogy to Kohn--Sham density functional theory.