[Pw_forum] About ZnO Slab

[Bipul Rakshit]

Dear Reza,
The vacuum is between the slab,  in c-axis,
while the a & b axis are infinite.

On Sun, May 10, 2015 at 11:12 PM, reza vatan <rezavatan64 at gmail.com> wrote:

> Hi Bipul,
>
> Just a question, How do you use 20 Angstrom vacuum in your calculation?
>
> Best,
> Reza
>
> On Fri, May 8, 2015 at 3:43 AM, Bipul Rakshit <bipulrr at gmail.com> wrote:
>
>> 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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>>>    Giuseppe Mattioli
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>>
>>
>>
>> --
>> Dr. Bipul Rakshit
>> Research Associate,
>> Institute of Physics (IOP),
>> Bhubaneswar- 751 005
>> Orissa
>> India
>>
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-- 
Dr. Bipul Rakshit
Research Associate,
Institute of Physics (IOP),
Bhubaneswar- 751 005
Orissa
India
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