[gmx-users] PME correction term

[Jason DeJoannis]

Sowmi,

  Imagine a system with only one charge, and it has
periodic boundaries. Therefore if you compute the 
energy of the ion due to all of its images, you 
will find that it diverges to infinity (similar to
the harmonic series). That is why it is necessary
to include a uniform compensating background charge
in non-neutral periodic systems. Because the 
background is uniform it does not give any net 
force to the charges.

  The only derivation I know of which includes
the neutralization is 

D. M. Heyes, JCP, v74, p1924 (1981).

which happens to be an interesting paper. Heyes
also mentions a paper by Bertaut which I have
not read.

  If you are interested only in application
of this method there is probably a more accessible
paper somewhere...

 Regards,

  -Jason

---
Jason de Joannis, Ph.D.
Chemistry Department, Emory University
1515 Pierce Dr. NE, Atlanta, GA 30322
Phone: (404) 712-2983
Email: jdejoan at emory.edu
http://userwww.service.emory.edu/~jdejoan



Quoting sowmianarayanan  r <sowmi80 at rediffmail.com>:

> Hi all,
> 
> I use PME to simulate an ion solvated in water to study the 
> hydration free energies. Hence typically I let my system be 
> charged. I understand that PME uses a correction term to account 
> for the charged system; but I do not know how exactly it is done. 
> Can anyone please help me find a reference probably where the 
> correction is explained...
> 
> ( I think, in EWALD summation an equal background compensating 
> charge is distributed...)
> 
> Thanks in advance
> Sowmi Rajamani
> Graduate STudent
> Rensselaer Polytechnic Institute
> 110 8th Street
> Troy NY 12180
> 
> 
> 
> 
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