[gmx-users] RE: Neutralising charge distribution

[Georgios Patargias]

Hi Jeroen

Thank you for your reply. I just wanted to know whether the correction 
term for the 'uniform background charge' is included in the code;  I didn't 
meant to to take it out.

Another thing is about the dipole correction that is applied for conducting 
boundary conditions. Is it switched off in PME when epsilon-surface is 0?

Regards 
George



-----Original Message-----
From: gmx-users-bounces at gromacs.org on behalf of van Bemmelen
Sent: Tue 9/18/2007 11:14 AM
To: gmx-users at gromacs.org
Subject: [gmx-users] RE: Neutralising charge distribution
 
Hi George,

Yes, such a correction term exists, but it's a divergent term. This term
is IMPLICITLY included in the energy, since it compensates for the
divergent part in the reciprocal space term, leaving a constant term.
This constant term is included explicitly in the code.

You could take this constant term out. But be very aware that this
constant term not only represents the 'uniform background charge' (or
'neutralising charge distribution', if you will) but also the divergent
part of reciprocal space term. So simply leaving it out would be highly
unphysical, at least in my opinion.

If you really want to know more, I suggest digging into the formulas
yourself. :-)

Greetz,
Jeroen


>Date: Mon, 17 Sep 2007 16:17:17 +0100
>From: "Georgios Patargias" <G.N.Patargias at leeds.ac.uk>
>Subject: [gmx-users] Neutralising charge distribution
>To: <gmx-users at gromacs.org>
>Message-ID:
>	<468DD857FE1E044DAE50E1D62FB57E70155D34 at HERMES4.ds.leeds.ac.uk>
>Content-Type: text/plain;	charset="iso-8859-1"
>
>Hello 
>
>I would like to ask what is the functional form of the uniform 
>neutralising charge distribution applied in Gromacs when doing 
>PME on a charged system. 
>
>Is there a correction term for this charge distribution that 
>is included in the calculation of energies?
>
>Thanks
>George
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