[Pw_forum] Zero of the electrostatic potential ?

[Stefano de Gironcoli]

The zero of the potential energy is the average electrostatic potential; 
as such the eigenvalues in different systems cannot be  directly compared.
what you need yo do is to calculate the (electrostatic) potential energy 
in the vacuum region where it should, at least for neutral systems,  be 
constant and take that as the zero of the energy.
In order to calculate the potential in the vacuum region one could adapt 
the example for the calculation of the Work Function in directory 
examples/WorkFct_example.

stefano
 
Vladan Stevanovic wrote:
> Dear Quantum-ESPRESSO users,
>
> I am using QE for simulations of transition metal clusters. My question 
> is where the code places the vacuum level in such calculations 
> (nonperiodic systems in a big cell) ? To formulate differently, is it 
> possible to compare directly KS eigenvalues from different calculations ?
>   

> Thanks,
> Vladan Stevanovic
>
> ---------------------------------------------
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> Station 3
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> e-mail : vladan.stevanovic at epfl.ch
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