[Pw_forum] Applying sawtooth filed parallel to a system

[Thomas Brumme]

Dear Ghadiyali Mohammed Kader,


the paper by Meyer and Vanderbilt does include a discussion about the 
"dipole correction".

The whole story (why a dipole correction is needed) is actually a little 
bit more involved and

not so important - you just need to know, that if you want to simulate a 
system in an electric

field, you also need to switch on the dipole correction in most cases.


Irrelevant details:


- Neugebauer and Scheffler wanted to simulate the adsorption of Na and K 
on Ag(111)

   (paper: Phys. Rev. B 46, 16067 (1992))

- to compensate the dipole within the system (to be able to use a 
3D-periodic boundary code)

   they introduced an external electric field (the sawtooth potential)

- Bengtsson showed that in this case it is actually not "external" but 
has an "internal" origin

   and that's why you have to multiply it by a factor of 1/2

   (paper: Phys. Rev. B 59, 12301 (1999))

- the paper by Meyer and Vanderbilt is more or less a summary of these 
details, i.e., that

   for the internal dipole (also the one induced by the external field) 
you have a slightly different

   equation (the prefactor and the internal dipole needs to be 
recalculated each scf step as the

   density changes)

- in VASP they actually don't cite the paper by Bengtsson but only state 
that a more general

   approach is chosen which does not include the mistake of the 
Neugebauer/Scheffler paper


Regards


Thomas


On 08.01.2018 13:36, Mohammed Ghadiyali wrote:
>
> Respected Sir,
>
>
> Thank you for the inputs.
>
> Can you suggest any paper/s where the dipole interaction is explained?
>
> The paper by Meyer and Vanderbilt do not cover it.
>
>
> Regards,
>
> Ghadiyali Mohammed Kader,
>
> Research Scholar,
>
> Dept. of Physics,
>
> University of Mumbai.
>

-- 
Dr. rer. nat. Thomas Brumme
Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry
Leipzig University
Phillipp-Rosenthal-Strasse 31
04103 Leipzig

Tel:  +49 (0)341 97 36456

email: thomas.brumme at uni-leipzig.de

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