# [Pw_forum] Doubt about dipole correction in ZnO

Giovanni Cantele giovanni.cantele at spin.cnr.it
Mon Apr 27 11:24:31 CEST 2015

```the emaxpos corresponds to the position of the maximum of the saw-like potential, so basically the position where the potential discontinuity occurs
(see in your plot for the 12 DL system, the discontinuity around ~ 52 A).

Now, if you do carefully see the last input you sent (for 8 DL), such a discontinuity occurs at ~ 0.8081 * 16.035 * 6.141 * 0.529177 A ~ 42.1 A. From the plot such a position
corresponds to the metallic Au layer, so your setting is wrong. The way in which you could figure out that there is something wrong (and not that there is a minimum ZnO width for obtaining the correct result) is that you cannot see any discontinuity in the potential plot (black line), even though you set it up in the input.

The cell size is 16.035 * 6.141 * 0.529177 A ~ 51.1 A, atoms go from ~ 14 to ~ 45 A, for a total width 45-14 A = 31 A. Being the vacuum space ~ 20 A, you can put the discontinuity at about z = 4 A (see 10 A far a way from the two closest Au and ZnO layers) => emaxpos = 4 / 51.1 ~ 0.08, if I did non mistakes.

Please check if this setting solve you problem.

Giovanni

> On 27 Apr 2015, at 10:13, Bipul Rakshit <bipulrr at gmail.com> wrote:
>
> Dear Giovanni,
> Here is the input file for the 8DL ZnO
>
> On Mon, Apr 27, 2015 at 1:32 PM, Giovanni Cantele <giovanni.cantele at spin.cnr.it <mailto:giovanni.cantele at spin.cnr.it>> wrote:
> Dear Bipul,
>
> it seems to me that you attached the input for the 12 ZnO double layer run, that is the one that works! Could you please send the one for 8 DL?
>
> Giovanni
>
>
>> On 27 Apr 2015, at 07:24, Bipul Rakshit <bipulrr at gmail.com <mailto:bipulrr at gmail.com>> wrote:
>>
>>
>> Dear PWscf Users,
>> I have one doubt on dipole correction applied. My case is Au-ZnO slab (6Au layer and 8/12 Double Layer of ZnO and 20 Angstrom Vacuum). With this mail I am sending pdf in which I ploted the potential vs Layers for 8 double layer (DL) and 12DL of ZnO. In both cases I applied dipole correction. But for 8 DL I didn't get the constant potential in vacuum. But for 12 DL i got it which is expected.
>> So is there any criteria that we have to choose some minimum Double Layer of ZnO to get the correct result. Or I am doing some mistake in calculation for 8 DL of ZnO because of which I am not getting the constant potential in vacuum. With this mail I am also sending my input file for dipole correction.
>> I am using experimental lattice constant and At first i relax the calculation till forces reaches to 0.001 Ry/au.
>> I am using GGA+U.
>> So if possible can you please tell me the reason for this.
>> regards
>>
>>
>> --
>> Dr. Bipul Rakshit
>> Research Associate,
>> Institute of Physics (IOP),
>> Bhubaneswar- 751 005
>> Orissa
>> India
>> <Dipole-ZnO.pdf><scf-dipole.in <http://scf-dipole.in/>>_______________________________________________
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> --
>
> Giovanni Cantele, PhD
> CNR-SPIN
> c/o Dipartimento di Fisica
> Universita' di Napoli "Federico II"
> Complesso Universitario M. S. Angelo - Ed. 6
> Via Cintia, I-80126, Napoli, Italy
> e-mail: giovanni.cantele at spin.cnr.it <mailto:giovanni.cantele at spin.cnr.it>
> Phone: +39 081 676910
> Skype contact: giocan74
>
> ResearcherID: http://www.researcherid.com/rid/A-1951-2009 <http://www.researcherid.com/rid/A-1951-2009>
> Web page: http://people.na.infn.it/~cantele <http://people.na.infn.it/~cantele>
>
>
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>
>
> --
> Dr. Bipul Rakshit
> Research Associate,
> Institute of Physics (IOP),
> Bhubaneswar- 751 005
> Orissa
> India
> <scf-dipole.in>_______________________________________________
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--

Giovanni Cantele, PhD
CNR-SPIN
c/o Dipartimento di Fisica
Universita' di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
e-mail: giovanni.cantele at spin.cnr.it
Phone: +39 081 676910
Skype contact: giocan74

ResearcherID: http://www.researcherid.com/rid/A-1951-2009
Web page: http://people.na.infn.it/~cantele

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