[CPMD-list] partial charges

[Axel Kohlmeyer]

On Wed, 30 May 2007, Robert fiske wrote:

robert,

RF> We are currently looking to do QM/MM free energy calculations using CPMD and 
RF> gromacs.  For these calculations we wish to vary the charge of the quantum 
RF> system.  Searching the list I read that CPMD does support partial charges, 
RF> but that problems can arise for optimization, CPMD is not used to optimize 
RF> the system when used with Gromacs but just to compute single point 
RF> calculations.

can you please be a bit more specific about _where_ you want
to use partial charges. also if you refer to previous messages
or threads in the mailing list archive, can you please
give the URL, so that we don't have dig/guess them for ourselves.
thanks.

in general you should always keep in mind that, the easier you make 
it for people to help you, the more likely you are to get help.

with CPMD you can use pseudopotentials with partial valence 
charge, but the total charge of the system has to be integer.

does that answer your question?

axel.

RF> Is using partial charges valid for this type of calculation?
RF> 
RF> Thank you for any assistance you can provide.
RF> 
RF> Robert Fiske
RF> Gogonea Group
RF> Cleveland State University
RF> 
RF> _________________________________________________________________
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RF> 
RF> 

-- 
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Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
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