[gpaw-users] How can the vacuum potential be found out

[Georg Kastlunger]

Dear Jens Jørgen,

Thank you very much for your help.

Now everything seems to be clear!

Best regards,
Georg Kastlunger



On 02/07/2012 08:11 AM, Jens Jørgen Mortensen wrote:
> On 06-02-2012 17:30, Georg Kastlunger wrote:
>>
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>> Thanks again for your help,
>> but unfortunately we are primarily interested in the case of periodic
>> boundary conditions.
>>
>> Is there maybe anybody else who might know how the zero energy is
>> defined in periodic cells?
>
> For that case, the average of the Coulomb potential is zero, where the 
> Coulomb potential is the potential we get from solving the Poisson 
> equation "nabla v_coulomb=4 pi rho", where rho is the pseudo charge 
> density.  The total effective potential is the v_coulomb+v_XC.
>
> Jens Jørgen
>
>> Regards,
>> Georg
>>
>>
>> On 02/06/2012 05:22 PM, Ask Hjorth Larsen wrote:
>> >  Hi
>> >
>> >  On Mon, 6 Feb 2012, Georg Kastlunger wrote:
>> >
>> >>  Which boundary do you mean?
>> >>  Is it the value at one certain point in the cell or an average of an
>> >>  interface between unit cells?
>> >>
>> >>  Best regards,
>> >>  Georg
>> >
>> >  The potential is zero at all the non-periodic cell boundaries.  This
>> >  means one cannot shift the potential arbitrarily - it is unique, and
>> >  so are the eigenvalues.
>> >
>> >  Each eigenvalue equals the derivative of the total energy with respect
>> >  to the occupation of the corresponding state (keeping wavefunctions
>> >  and density constant).
>> >
>> >  (The same is not true if the cell is fully periodic; then I'm not sure
>> >  what determines the potential and eigenvalues)
>> >
>> >  Regards
>> >  Ask
>> >
>> >
>>
>
>
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