[Pw_forum] Problem with pseudopotential

[Stefano Baroni]

On Mar 29, 2011, at 1:44 AM, Izaak Williamson wrote:

> Dear all,
> I was trying to calculate the workfunction for Cu(100) surface. When I plotted the planar average of Vbare+VH as a function of z, I found that Vbare+VH at some points is higher than Vbare+VH at the vacuum level. I have attached the file (planar-average-pbedrrkjus.pdf). I am also attaching the input file Cu100.in. Does this mean that the pseudopotential (Cu.pbe-d-rrkjus.UPF) is wrong?

No. (I mean, not necessarily)

> Why does it behave like this? 

Why not?

> When I do the same calculation with Cu.pbe-n-van_ak.UPF pseudopotential, then I get a reasonable graph (planar-average-pbevanak.pdf). Any suggestions/explanations would be greatly appreciated. 

the value of the bare potential at any atomic core is to a large extent arbitrary, and depends on many (unphysical) details of the pp construction, such as the choice of the core radius, the pseudization algorithm, the choice of the angular-momentum channel to be selected as reference ("local") potential ...

> Thank you.

you are most welcome
Stefano B

---
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

Please, if possible, don't  send me MS Word or PowerPoint attachments
Why? See:  http://www.gnu.org/philosophy/no-word-attachments.html



-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20110329/579ee27f/attachment.html>