The NDDO Approximation

The Neglect of Diatomic Differential Overlap is the next level of approximations used in semiempirical quantum chemistry and the basis of most modern semiempirical methods based on the Hartree-Fock method.

NDDO.pdfDownload

Here the most important methods came from the school of Michael Dewar. One should mention the MNDO, AM1, PMx and RM1 as being some of the most influential and used NDDO methods.

MNDO,AM1.pdfDownload

PM3.pdfDownload

RM1.pdfDownload

PM6.pdfDownload

There are other methods worth referencing, even though we do not explore them in further detail.

otherNDDO.pdfDownload

In themselves, semiempirical MO theory is still quite limited in its predictive power. It is however possible to get more information from these methods by adding further extensions. Charge models aim at introducing a better description of partial charges, so that observables like molecular dipole moments are more accurate.

SEcharges.pdfDownload