Dear Members,
I'm relatively new to Amber8. I am trying to detemine charges for small
molecules (less than 50 atoms) using resp that are conformation independent. I
used a systematic torsion angle serach for my molecue using Insight II. From
this search I kept only the 10 lowest energy conformations according Insgith II
force field. For each one of this conformations I used Gaussion to calculate
the ESP charges in two steps. First I did an optimisation using "STO-3G" and
"opt pop=none geom(nodistance,noangle)" as keywordks. With the output file I
made the ESP calculation using "6-31G*" and "iop(6/33=2) pop=mk" as keywords.
After that I used resp with all my molecules to calculate the RESP charges. At
the end of the calculation, I saw that the results of RESP did not gave the
mean values for 10 conformations, but charges for each conformation. My
questions are:
1. If I use 10 conformations for charges determinantion, after using RESP for
the 10 conformations, do I have to take the mean value of the 10 molecules or
is there a specific command in resp that allows it to do that directly?
2. When I am working with enantiomers in Amber8, should we used the same
charges for both enantiomers or have we to calculate the charges for
(R)-enantiomers AND for (S)-enantiomers? (my molecules have only one chiral
centre).
Thank you very much for your help.
..
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Received on Thu Jan 26 2006 - 06:10:06 PST
