[Pw_forum] About ZnO Slab

[Bipul Rakshit]

Thanks Giuseppe for your reply.
Yes I do agree that there is a large dipole. But I also tried to apply the
dipole correction (input attached ), but still it is not converging. This
time I am using 20 Angstrom vacuum. But still its not converging.

On Fri, May 8, 2015 at 2:23 PM, Giuseppe Mattioli <
giuseppe.mattioli at ism.cnr.it> wrote:

>
> Dear Bipul
> I've tried to run your input file, and I suppose that your calculation
> does not converge because of the strong vertical dipole related to the 0001
> wurtzite slab, which you could try to visualize by calculating the planar
> average of the KS potential. My suggestion is to increase the vacuum to
> decouple the images, but it could be not sufficient, because the dipole
> should be quite strong. This is also a good reason for strange work-function
> numbers. AFAIK the polar ZnO surfaces are rarely exposed in real systems.
> The most stable and common surface is the nonpolar (10-10) one, which does
> not usually show any convergence problem. Buy you know what surface you
> need...
> HTH
> Giuseppe
>
> On Friday, May 08, 2015 12:29:25 AM Bipul Rakshit wrote:
> > Dear users,
> > I am doing ZnO slab calculation with 12 Double layer of ZnO. Since ZnO
> is a
> > wide band-gap material, so I am using occupation=fixed. I attached my
> input
> > also.
> > But why the calculation is not converging?
> >
> > But when I am using occupation=smearing, it do converge. But it gives a
> > work function of 3.47 eV after applying the dipole correction.
> >
> > So what mistake I am doing?
> >
> > Please help me in this regards
>
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-- 
Dr. Bipul Rakshit
Research Associate,
Institute of Physics (IOP),
Bhubaneswar- 751 005
Orissa
India
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