[gmx-users] PME question

David van der Spoel spoel at xray.bmc.uu.se
Wed Jun 19 13:34:30 CEST 2002

On Wed, 19 Jun 2002, Marc Baaden wrote:

>Hi Erik (and all others on this thread),
>lindahl at stanford.edu said:
>>> Well, imagine you have a charge -1 in the center of the box, and +1
>>> next  to one of the box sides. This will give you a net dipole in the
>>> system. Now, if the +1 charge moves across the box boundary and
>>> reappears on the other side the dipole will suddenly have the opposite
>>> direction after a discrete instantaneous jump. 
Actually it is not even true I think... It is just a dipole which moves
slowly in  an infinite system (well, as many k-vectors as you have). The
dipole of the box will change, but not the interaction with the other

>I think that's a very interesting point, although I guess that as the dipole
>depends on the distance between the charges, the effect should be quite small
>if the box is 'reasonably sized' (maybe >3 nm ?).
>Is there any more systematic analysis of that kind of problem/artefact ?
>  Marc
> Dr. Marc Baaden - Laboratory of Molecular Biophysics, Oxford University
> mailto:baaden at smplinux.de  - ICQ# 11466242 -  http://www.marc-baaden.de
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Groeten, David.
Dr. David van der Spoel, 	Biomedical center, Dept. of Biochemistry
Husargatan 3, Box 576,  	75123 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://zorn.bmc.uu.se/~spoel

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