Subject: Questions about charges

From: [email-masked] (Charles Martin)
Date: Mon, 26 Sep 1994 14:01:19 -0600 (CDT)

Dear all:
	
	Recently Feng Zhou has asked:

>         We have performed a charge calculation using the program  GAUSSIAN92
>(6-31G, AM1),   the charges calculated seems somewhat larger than the charges
>given in  commerical packages such  as CHARMm.    Can anybody tell me is
>that a convention to rescale the charges given by GAUSSIAN  to compare
>with other programs such as  MOPAC?    What  should be  the scaling factor?
>
I would like some of the experts out there to explain some of these
charge fitting schemes to me as well.   For example, are there studies
which describe in detail how the charges are derived and which  test the
how well the choices of charges reproduce properties as compared with those
computed with high level, correlated calculations and with experiment?  
How sensitive are the computed properties to the choice of the charges?
How sensitive are HF charges to the choice of basis set?  How do the
charges change when using correlated densities (either from DFT or correlated 
ab initio calculations).  

With Best Regards
Chuck
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Charles H. Martin

email: [email-masked]

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