[gmx-users] Question PME+charged groups

Erik Lindahl lindahl at stanford.edu
Thu May 16 20:51:58 CEST 2002

David van der Spoel wrote:

>On Wed, 15 May 2002 ehab at biof.ufrj.br wrote:
>>Sorry if this question sounds trivial, but there is any sense in using charged
>>groups with PME calculations?
>Yes, that's when you need it most. Preferably your system should be
>overall neutral
I'm not quite sure how you're thinking here David; Of course the total 
system should be neutral, but it isn't actually necessary to group atoms 
into neutral (or nearly neutral) charge groups. The reason we do it is 
that that it makes the neighborsearching faster - we only need to search 
charge group centers! Unless you have extremely large charge groups it 
won't affect the result, so it's a win-win.



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