[QE-users] VACUUM POTENTIAL NOT ZERO CALULATION

[Lorenzo Paulatto]

> *_What I did:_*
> 1) scf with pw.x
> 2) pp.in <http://pp.in> with pp.x
> 3) using a code to find the planar average electrostatic potential in 
> the z (vacuum) direction. As I could not figure out how to use the 
> average.x tool.
Which code, and what is wrong with average.x in your case?
> 4) identify the vacuum potential, which in my case is not zero (should 
> be zero as written in literature 
> https://doi.org/10.1016/j.ijhydene.2022.09.249).

It is not zero, it is taken to be zero, that's the entire point of this 
calculation: to find the zero.

More specifically, when you do a calculation in periodic boundary 
conditions, you set the zero so that the average of the local potentials 
is zero, which is not the same as setting the vacuum (i.e. infinite 
distance) potential to zero.

>
> all the files are attached.
>
> *_My question is that:_*
> 1) is my method correct ?
> 2) if yes then why is the vacuum potential non zero? What can I do to 
> make it zero ?
> 3) I am trying to find the vacuum potential so that I can calculate 
> work function and vbm cbm values with respect to vacuum potential for 
> photocatalytic application.

You found it, that is your zero

hth


>
> Kindly help me. I have been stuck at this for a long time.
>
>
> google drive link 
> <https://drive.google.com/drive/folders/1knK2PNlKFH26ri84sLJGKM2LVRN789BC?usp=sharing> . 
> I have attached all the files in the google drive link. If you can't 
> read it I'll send in whichever manner needed.
>
>
> Ashley Cooper
> Phd
> Assam University Silchar
> Assam, India
>
>
>
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-- 
Dr. Lorenzo Paulatto
IR IMPMC - CNRS UMR 7590 / Sorbonne Université / MNHN
phone: +33 (0)1 442 79822 / telegram: lpaulatto
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