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. > > -Justin >
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