WHAT IS DMM

In the previous sections we performed a sequence of moves intended to bridge the gap between an approximate QM description of molecular electronic structure and a classical representation of the PES of organic molecules suitable for further parametriza-tion and simplifications in order to reach a scheme similar to molecular mechanics i.e. classical force fields. This construct can be qualified as deductive molecular mechanics (DMM) as each of its components has a transparent counterpart in the underlying 

The importance of the transferability of the geminals has been pointed out in [62], It was stated that the assumption of the transferability of the geminal amplitudes is a prerequisite for that of the bond energy. However, in [62] geminal transferability has not been proven and the authors concentrate on the statements equivalent to the transferability of the MM bond stretching force fields. Our proof of course strongly relies on the SLG form of the trial wave function. This may seem to be a very strong restriction on the proposed derivation scheme. However, it is not a restriction at all if 

The local character of the orbitals used throughout the derivation is inherent for the suggested approach and the specific form of the orbitals of interest appears as a result of energy minimization procedure, which allows us to avoid a posteriori localizations complemented by poorly defined tail cutting . The locality of the orbitals used in the SLG picture is in sharp contrast to the standard HFR treatment leading to delocalized orbitals. 

It remains to find out whether a similar treatment can be developed for the torsion force fields habitually indexed by quadruples of atomic types and thus posing most problems in the prescription of parametrization. One can also think about following problem setting, namely of designing a set of MINDO/3 or NDDO parameters selected for using with the formulae of either of the approximations of the DMM family. In this case, the entire parameter set can be indexed by the only atomic types as no parameters indexed by pairs and even more by triples or quadruples of atomic types are previewed in a semiempirical setting. 

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