[gmx-users] Error note
gmelaugh01 at qub.ac.uk
Thu Feb 23 15:10:15 CET 2012
I am using 4.5.5
Justin A. Lemkul wrote:
> Gavin Melaugh wrote:
>> Hi Justin
>> I saw this and had a question.
>> How important is it for a charge group to be neutral?
> It isn't. Conventional use dictates that the charge group bear an
> integral charge. With PME, this is not necessary. Many force fields
> do not use charge groups at all (i.e., single-atom charge groups).
>> In one of my systems I model a solvent of crown ethers using an all atom
>> model. The smallest neutral unit comprises a CH2-O-CH2 (7 atoms). I have
>> used this as a charge group to and get no warnings.
> The only implication I can think of would be in neighbor searching.
> If the group is large, then short-range forces may not be calculated
> accurately. The warning from grompp was a recent addition to the
> code; if you're using an older version you may not have triggered it.
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