CHARMM MOPAC

Table 3 lists chemists who have been most cited in chapters of prior volumes of our book series. Not surprisingly, all those listed are computational chemists, and many have written a chapter for Reviews in Computational Chemistry. It is interesting to notice how frequently the listed individuals are associated with developing a computer program that is well known in the lexicon of computational chemistry AMBER, CHARMM, Gaussian, UHBD, GROMOS, MM2/MM3, ECEPP, BOSS, DGEOM, MOPAC, DOCK, and so forth. 

Field et al. use for the QM part semiempirical MNDO and AM 1 methods drawn from the MOPAC package,and for the MM part of the force field provided by CHARMM. Dummy atoms are hydrogens they experience forces from other QM atoms and exert forces on them. MNDO and AM 1 parameters are a little adjusted, and the MM force field is modified to allow electrostatic interactions between QM and MM atoms which are at a distance of less than three bonds. CHARMM is an integrated package, also allowing MD simulations to be performed ( s20 ps on 2000 MM atoms plus 50 QM atoms, in the first version of this program). 

The partial charges were derived from semi-empirical quantum - mechanical calculations using MOPAC 6.0 with the AMI Hamiltonian [12]. Due to computational limitations, the partial charges of the macrocyclic core and of the ester substituents were calculated separately. The final charge set is shown in fig. 1. The benzene of crystallisation was included using CHARMM 22 parameters [13]. A full list of the parameters will be published elsewhere. 

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