[Pw_forum] About ZnO Slab

[reza vatan]

Dear Bipul,

Thanks for replying.

On Sun, May 10, 2015 at 12:04 PM, Bipul Rakshit <bipulrr at gmail.com> wrote:

> 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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>>
>>
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>
>
> --
> Dr. Bipul Rakshit
> Research Associate,
> Institute of Physics (IOP),
> Bhubaneswar- 751 005
> Orissa
> India
>
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