[gmx-users] CHARMM forcefield

[simon sham]

Hi,
I have two questions about using the charmm force field. 
1. Do we still need to use the two perl scripts, convert_charmm_ to_gromacs.pl and fix_top_for_charmm.pl?
2. I got the following note when I tried to do energy minim. with grompp:

NOTE 1 [file topol.top]:
  The largest charge group contains 12 atoms.
  Since atoms only see each other when the centers of geometry of the charge
  groups they belong to are within the cut-off distance, too large charge
  groups can lead to serious cut-off artifacts.
  For efficiency and accuracy, charge group should consist of a few atoms.
  For all-atom force fields use: CH3, CH2, CH, NH2, NH, OH, CO2, CO, etc.

Is this a problem?

Thanks for your insight!

Simon
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