[Pw_forum] ion problem

[Cyrille Barreteau]

Dear all

I have a question related to this problem.
I am interested in the study of charged clusters.
If I understand well, due to to the periodicity of the plane wave codes
one has to substract the correct "background" in order to keep the
energy from going to infinity..

I would like to compare the energy of clusters with different
charges -e -2e etc... Do you have some advices to do such calculation?
Is it necessary to take even larger supercells than for neutral clusters?

thanks in advance

  cyrille

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Cyrille Barreteau  | phone : +33 (0)1 69 08 29 51
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Stefano de Gironcoli wrote:

>Unless you put some constraint the code will distribute the charge 
>density so as to minimize the total energy. If the atoms behaves as ions 
>in your cluster this will be automatically found by the code.
>A way (one of the many arbitrary ways) to measure this atomic charge is 
>to project the wfc on atomic orbitals and counts how many electrons are 
>projected on each atom... this is done by projwfc.x in the PP directory.
>If you want to force the system to do something else w.r.t. what it 
>would do automatically you need to add some constraint. For instance in 
>a non collinear magnetic calculation one can constraint the size of the 
>atomic magnetization, its direction or one of its commponents. In the 
>cvs version magnetization size can be constrained also in the collinear 
>case.
>Currently there is no constraint on the atomic charge but using the 
>constrained_magnetization part as template should not be too difficult 
>implement such a feature.
>
>Hope this helps,
>
>Don't forget to sign your posts including your affilation.
>
>Stefano de Gironcoli, SISSA and DEMOCRITOS
>
>Rudra Banerjee wrote:
>  
>
>>dear PWSCF users,
>>I am new to pwscf and stuck in a question.......is there any way to 
>>put anion   or cation    as a unit?the total cluster is charge less 
>>but have two different types of ion.......can anyone tell me what to 
>>do in this situation?
>>Regards
>> 
>>-- 
>>Rudra
>>Have a Nice Time
>>http://www.bose.res.in/~rudra <http://www.bose.res.in/%7Erudra>
>>Please, if possible, don't send me MS Word or PowerPoint attachments
>>Why?See: http://www.gnu.org/philosophy/no-word-attachments.html
>>
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