Other Changes in Functional Form

Two modifications to the fundamental forms of modem NDDQ functions have been reported recently that merit particular attention. First, Weber and Thiel (2000) have reconsidered the 

A second modification recently described by Repasky, Chandrasekhar, and Jorgensen (2002) focuses on improving the core-repulsion functions in MNDO and PM3. In particular, they define a pairwise distance directed Gaussian function (PDDG) to compute a contribution to the nuclear repulsion energy between atoms A and B as 

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