[QE-users] Regarding bands

[Giovanni Cantele]

Dipole correction might certainly being a point, also given that you are considering a polar system. 

So you could try to share in/out files including dipole correction.

Moreover, you should also try to understand whether or not the metallicity you find is a spurious effect or not. 
Try, for example, to make a plot of the averaged potential along direction orthogonal to the heterostructure, to see if it looks reasonable. 
Also you could make charge transfer plots, again to guess if they provide at least reasonable results or unphysical patterns.
Another point: are you SURE that you have correctly matched the Si surface to the ZnO? Indeed, you said that after removing the ZnO, you find a gap. Could it be that metallicity is induced by “surface” (in this case “interface”) states of Si(100)? Depending on its reconstruction, Si(100) can show surface states with different or no gap between occupied and unoccupied states, as far as I remember.

Giovanni

> On 28 Apr 2022, at 13:38, Satyasiban Dash ph19d005 <ph19d005 at smail.iitm.ac.in> wrote:
> 
> Yes . Thank you for the clarification. I am trying to match (0001) surface. But I have observed upon relaxing ZnO loosing its symmetry and this may be due to the polar surfaces but experimentally we do observe a band gap. I have also tried dipole correction but results are same. But if I remove Si its giving a gap. Is there anyway to reproduce it with Si (001).
> 
> On Thu, 28 Apr, 2022, 4:55 pm Giovanni Cantele, <giovanni.cantele at spin.cnr.it <mailto:giovanni.cantele at spin.cnr.it>> wrote:
> Dear Satya,
> 
> it is not that easy (at least for me) to provide an answer to your question using the data you have provided. Maybe the output files (of scf and bands) and a plot of your band structure might help to infer if there is any issue in your calculation.
> 
> However, before wondering whether you get a metal whereas experiments measure a gap, you should also check that you are simulating a system that is as close as possible to the experimental one (in terms of thickness and/or surface orientation of both ZnO and Si, and so on). As far as the atomic positions are concerned, they look reasonable. It seems (if I’m not wrong) that you are trying to match a Si(100) surface with a ZnO(0001) surface, aren’t you? Is this what you expect?
> 
> Giovanni
> 
> -- 
> 
> 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: https://sites.google.com/view/giovanni-cantele/home <https://sites.google.com/view/giovanni-cantele/home>
> 
> 
>> On 28 Apr 2022, at 07:09, Satyasiban Dash ph19d005 <ph19d005 at smail.iitm.ac.in <mailto:ph19d005 at smail.iitm.ac.in>> wrote:
>> 
>> Dear Users
>>  I have been trying to calculate a heterostructure with a slab model. I have followed most of the examples given in the forum and tried it still I am getting a metallic band structure. I have used the K-path generation tool provided in "material project" website  to generate k-path. I have given the scf and bands.in <http://bands.in/> file as attached files. Please have a look. Experimentally this system has a wide band gap.
>> 
>> 
>> Thanks.
>> Satya
>> Research Scholar
>> IIT Madras.
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