Thank you for your response. On Thu, 28 Apr, 2022, 5:57 pm Giuseppe Mattioli, < [email protected]> wrote:
> > Dear Satya > > Like Giovanni, I also don't know why you don't obtain what you expect. > But I want to offer my own penny to the discussion. > > 1) Due to the well known effect of delocalization errors in GGA-DFT, > the band gap of Si is generally reduced to around 0.6 eV. The > reduction involves both the lowering of the conduction band potential > and the raising of the valence band potential. In the case of ZnO you > have a strongly curved conduction band around the minimum at Gamma, > which is not affected by delocalization errors, and a very problematic > valence band, in which the interaction between the narrow O 2p and Zn > 3d contributions may raise the valence band maximum by more than 2 eV, > shrinking the band gap to less than 1 eV in bulk ZnO. > > 2) First of all, therefore, I would check *in the same supercell* if > isolated Si and isolated ZnO slabs envisage a metallic character of > the junction due to the unsymmetrical band gap underestimation of the > two parts. > > 3) The most stable ZnO surface is (10-10), not 0001 (or its 000-1 > counterpart having reverse polarity). The polar surfaces of ZnO are > tricky to simulate as slabs due to the strong polarity of the Zn-O > bond. In the past, I obtained some weird layered hexagonal structure > similar to BN! I suppose that the choice of (0001) is purposeful. If > it is not, try to reconsider your choice. > > 4) Such a strongly polar surface in contact with a non-polar Si > surface may induce a huge interfacial charge transfer, even enhanced > by delocalization errors mentioned above, or can lead to significant > shifts of band edges, yielding a metallic character of the > semiconductor junction. > > HTH > Giuseppe > > Quoting Satyasiban Dash ph19d005 <[email protected]>: > > > 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, < > > [email protected]> 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: [email protected] <[email protected]> > >> Phone: +39 081 676910 > >> Skype contact: giocan74 > >> > >> ResearcherID: http://www.researcherid.com/rid/A-1951-2009 > >> Web page: https://sites.google.com/view/giovanni-cantele/home > >> > >> > >> On 28 Apr 2022, at 07:09, Satyasiban Dash ph19d005 < > >> [email protected]> 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 file as attached files. Please have a look. > >> Experimentally this system has a wide band gap. > >> > >> > >> Thanks. > >> Satya > >> Research Scholar > >> IIT Madras. > >> <scf.in><job576185.pw.in > >_______________________________________________ > >> The Quantum ESPRESSO community stands by the Ukrainian > >> people and expresses its concerns about the devastating > >> effects that the Russian military offensive has on their > >> country and on the free and peaceful scientific, cultural, > >> and economic cooperation amongst peoples > >> _______________________________________________ > >> Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > >> users mailing list [email protected] > >> https://lists.quantum-espresso.org/mailman/listinfo/users > >> > >> > >> _______________________________________________ > >> The Quantum ESPRESSO community stands by the Ukrainian > >> people and expresses its concerns about the devastating > >> effects that the Russian military offensive has on their > >> country and on the free and peaceful scientific, cultural, > >> and economic cooperation amongst peoples > >> _______________________________________________ > >> Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > >> users mailing list [email protected] > >> https://lists.quantum-espresso.org/mailman/listinfo/users > > > > GIUSEPPE MATTIOLI > CNR - ISTITUTO DI STRUTTURA DELLA MATERIA > Via Salaria Km 29,300 - C.P. 10 > I-00015 - Monterotondo Scalo (RM) > Mob (*preferred*) +39 373 7305625 > Tel + 39 06 90672342 - Fax +39 06 90672316 > E-mail: <[email protected]> > > _______________________________________________ > The Quantum ESPRESSO community stands by the Ukrainian > people and expresses its concerns about the devastating > effects that the Russian military offensive has on their > country and on the free and peaceful scientific, cultural, > and economic cooperation amongst peoples > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users
_______________________________________________ The Quantum ESPRESSO community stands by the Ukrainian people and expresses its concerns about the devastating effects that the Russian military offensive has on their country and on the free and peaceful scientific, cultural, and economic cooperation amongst peoples _______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
