[gmx-users] Non-zero system charge

[David van der Spoel]

David Mobley wrote:
> Itamar,
> 
> But if the charge weren't neutralized, the electrostatic energy would
> be infinite, since an infinite lattice of charged unit cells has
> infinite charge and hence infinite interaction energy. (So the trivial
> check, of course, is to see whether the energy is infinite if you run 
> with a charged system. The answer is no).

In PME there are charge and dipole corrections.
With cut-offs it doesn't matter.

> 
> David
> 
> On 3/31/06, Itamar Kass <ikass at cc.huji.ac.il> wrote:
> 
>>Shalom Bob,
>>
>>First GROMACS does not nutrelize the charge it will run the system as is, you
>>have to nutrelzie it manually.
>>
>>I know this was discussed few weeks ago, please search the mailiong list.
>>
>>
>>good work, Itamar.
>>
>>
>>Quoting Bob Johnson <robertjo at physics.upenn.edu>:
>>
>>
>>>Hello everyone,
>>>I am using PME to handle electrostatics. What happens if I run a simulation
>>>with
>>>a non-zero net charge? Does GROMACS automatically provide some sort of
>>>background charge to neutralize the system?
>>>Thanks,
>>>Bob Johnson
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>>
>>
>>
>>
>>===========================================
>>| Itamar Kass
>>| The Alexander Silberman
>>| Institute of Life Sciences
>>| Department of Biological Chemistry
>>| The Hebrew University, Givat-Ram
>>| Jerusalem, 91904, Israel
>>| Tel: +972-(0)2-6585194
>>| Fax: +972-(0)2-6584329
>>| Email: ikass at cc.huji.ac.il
>>| Net: http://www.ls.huji.ac.il/~membranelab/itamar/itamar_homepage.html
>>============================================
>>
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> 
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-- 
David.
________________________________________________________________________
David van der Spoel, PhD, Assoc. Prof., Molecular Biophysics group,
Dept. of Cell and Molecular Biology, Uppsala University.
Husargatan 3, Box 596,  	75124 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://folding.bmc.uu.se
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