Modified ZDO methods

This helped to build a robust tool for modeling thermochemistry and molecular structure of organic molecules yet in the 70s. The MINDO/3 parametrization covers H, B, C, N, O, F, Si, P, S, and Cl atoms, although for some atomic pairs the q.ab and 

The MNDO (modified NDDO) parametrization [64] involves the core-core repulsion in the form  

The methods of the NDDO family were further developed, which resulted in two quite successful parametrizations for organic species [68,69] known as the Austin Model (AMI) and Parametrized Model (PM3) and further, PM5 and SAMI (semi-ab initio model) parametrizations [74,75]. 

The AMI and PM3 parametrizations can be characterized as the MNDO ones with the core-core energy terms further modified  

and At. However, due to the automatism in some cases, the values of the fitted parameters do not follow the intuitive monotonous series along the rows of the Periodic Table. E.g. the parameters for phosphorus fall out from the monotonous sequence along the row. More recent analysis indicates that this happens due to the fact that experimental values for phosphorus compounds used in the parametrization turned out to be wrong by 140 kcal/mole. 

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