[QE-users] Local charge

[Robert Molt]

Without knowing your system, it is impossible to comment on whether the 
concept of local charge exists, meaningfully. Can you specify your system?

For example, there is no such thing as a widely-accepted method to 
calculate local charge because the concept of local charge does not 
exist, rigorously. No law of physics demands that electrons are "owned" 
by a certain atom (Coulomb's law neither knows nor cares about the human 
concept of atoms). In some cases, electrons' positions happen to be 
relatively localized (like, say average organic molecules), and the term 
has more meaning. If we are talking about a highly delocalized system, 
the term has no meaning (because the electrons don't "belong" to anyone).


On 8/11/18 3:25 PM, Comer, Benjamin M wrote:
>
> Mr. Hosseini,
>
> I am not sure what type the local charges and magnetizations QE prints 
> by default, but you should use a widely accepted method to calculate 
> local charges, such as Bader analysis. I should note that there is no 
> “correct” way to calculate a local charge. However, there are many 
> ways to calculate charges developed by the community, each with it’s 
> own drawbacks (see Wikipedia link below.) I’d recommend using Bader 
> charges, DDEC6, or the lowden charges printed out from the projwfc.x 
> code in the quantum espresso suite(links below.)
>
> https://en.wikipedia.org/wiki/Partial_charge
>
> http://theory.cm.utexas.edu/henkelman/code/bader/
>
> https://sourceforge.net/projects/ddec/files/
>
> http://phya.snu.ac.kr/~nmcuong/board/physics/INPUT_PROJWFC.html 
> <http://phya.snu.ac.kr/%7Enmcuong/board/physics/INPUT_PROJWFC.html>
>
> Hope it helps,
>
> Ben Comer
>
> Georgia Tech
>
> >Dear All
>
> >
>
> >I need to compute local charge of atoms in my unit cell. As I checked, the 
> output of SCF provides local charge with the corresponding 
> >magnetization. The numbers are confusing. How can I compute the local 
> charge?
>
> >
>
> >M.R.Hosseini
>
> >Tarbiat Modares University, Department of Chemistry, Iran
>
>
>
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-- 
Dr. Robert Molt Jr.
r.molt.chemical.physics at gmail.com

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