[MMTK] H+ in water

Konrad Hinsen hinsen at cnrs-orleans.fr
Sat Mar 17 15:10:41 UTC 2007


On 16.03.2007, at 16:45, Davide Ricci wrote:

> a stupid question...Suppose I want to study H+ in water, so that  
> the total charge of the system is +1. Can I do this in a Periodic  
> Universe in MMTK? Or Do I have to use a Finite Universe ?

You can do that in a periodic universe. However, when you start  
calculating energies, you should be aware of the consequences. In  
principle, the energy of a charged periodic system is infinite.  
Depending on the electrostatics method chosen, there may be problems  
due to that, or unexpected effects. Ewald summation, for example,  
adds a uniform charge density to the system that neutralizes the  
total charge. That may or may not be what you want.

Konrad.
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Konrad Hinsen
Centre de Biophysique Moléculaire, CNRS Orléans
Synchrotron Soleil - Division Expériences
Saint Aubin - BP 48
91192 Gif sur Yvette Cedex, France
Tel. +33-1 69 35 97 15
E-Mail: hinsen at cnrs-orleans.fr
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