Hydrogen bond parametric treatment

Such specialized semiempirical treatments exist (see Ref. [42] for a review on early work), many of which are based on the MNDO model in one of its standard implementations. For example, there are several early MNDO and AMI variants with a special treatment of hydrogen bonds [42], which have recently been supplemented with an elaborate PM3-based parametrization for water-water interactions named PM3-PIF (pair interaction function) [69]. These special approaches exploit the flexibility offered in MNDO-type methods by the presence of the effective core-core repulsion term which can be modified for fine tuning. 

Finally, several special MNDO parametrizations are available for certain classes of compounds or for specific properties. These treatments retain the original MNDO approach (a)-(c), but use parameters (d) that have been optimized for the intended applications. It is obvious that such specialized methods ought to be more accurate in their area of applicability than the original general-purpose MNDO method. Samples of this kind include the special MNDO variants for small carbon clusters, fullerenes, and hydrogen-bonded systems as well as special parametrizations for electrostatic potentials. ... 

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