[Pw_forum] Work function calculation

[Stefano Baroni]

On May 6, 2012, at 6:01 AM, vasudevan m.v wrote:

> Dear all
>                           I was trying to calculate work function of Au(111) surface using Quantum Espresso 4.2.1. I used a 9 layer slab along with 22Å vacuum. I first did a relax calculation and then post processing to extract potential (sum of Coulomb potential and Hartree part ) . Then took the planar average of this potential. I got a strange graph which I have attached with this mail. 
> 
> 1 Why shape of graph is coming like this ?

why shouldn't it? what is wrong with that, according to your expectations?
 
> 2 What is the need of excluding exchange correlation potential in calculating Work function ?

because the exchange potential converges more slowly to the vacuum limit, due to its \rho^{1/3} behavior ...

> I changed the pseudo potential and obtained same pattern of graph.

I would be surprised if you didn't

SB


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Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center - Trieste
http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)

La morale est une logique de l'action comme la logique est une morale de la pensée - Jean Piaget

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