Getting the correct band gap from DFT is usually a coincidence due to the approximations made in exchange and correlation potential.
You can try GW calculations on top of the DFT ground state, in QE you can use YAMBO. In addition to the above you also have to consider if your experimental value is a single particle excitation or a two particle (electron hole excitation). In the latter case you might need to solve the BSE. Hth Chris On Fri, Sep 27, 2019, 7:01 PM <users-requ...@lists.quantum-espresso.org> wrote: > Send users mailing list submissions to > users@lists.quantum-espresso.org > > To subscribe or unsubscribe via the World Wide Web, visit > https://lists.quantum-espresso.org/mailman/listinfo/users > or, via email, send a message with subject or body 'help' to > users-requ...@lists.quantum-espresso.org > > You can reach the person managing the list at > users-ow...@lists.quantum-espresso.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of users digest..." > > > Today's Topics: > > 1. What Is Estimated SCF Accuracy (Ben Comer) > 2. Re: What Is Estimated SCF Accuracy (Paolo Giannozzi) > 3. Re: What Is Estimated SCF Accuracy (Ben Comer) > 4. VC-relax in polar materials (Eric Glen Suter) > 5. Convergence of Ecutwfc and Ecutrho for Doublet Occupation > Scheme (Brendan Smith) > 6. Re: What Is Estimated SCF Accuracy (Ben Comer) > 7. Re: What Is Estimated SCF Accuracy (Paolo Giannozzi) > 8. problems in graphene simulation (Haider Abbas) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Thu, 26 Sep 2019 14:51:42 +0000 > From: Ben Comer <bcom...@gatech.edu> > To: "users@lists.quantum-espresso.org" > <users@lists.quantum-espresso.org> > Subject: [QE-users] What Is Estimated SCF Accuracy > Message-ID: <7746af3e-46b8-bfcb-734c-66a97822c...@gatech.edu> > Content-Type: text/plain; charset="utf-8" > > Hello, > > I'm trying to understand what exactly estimated SCF accuracy is. Does > anyone know where I can find a formal definition of what it is and how > it is being calculated? The structure of the output file implies that it > is related to the Harris-Foulkes and the total energy, but it is clearly > not the trivial difference between these two quantities. > > Thanks in advance, > Ben Comer > Georgia Tech > > > ------------------------------ > > Message: 2 > Date: Thu, 26 Sep 2019 16:57:46 +0200 > From: Paolo Giannozzi <p.gianno...@gmail.com> > To: Quantum ESPRESSO users Forum <users@lists.quantum-espresso.org> > Subject: Re: [QE-users] What Is Estimated SCF Accuracy > Message-ID: > <CAPMgbCurAsE9CU_XF7h5jE38p= > u1g8amjtt51-_7scyorg4...@mail.gmail.com> > Content-Type: text/plain; charset="utf-8" > > If I remember correctly: Eq.A6 of J.Phys.: Condens. Matter 21, 395502 > (2009) > > Paolo > > On Thu, Sep 26, 2019 at 4:52 PM Ben Comer <bcom...@gatech.edu> wrote: > > > Hello, > > > > I'm trying to understand what exactly estimated SCF accuracy is. Does > > anyone know where I can find a formal definition of what it is and how > > it is being calculated? The structure of the output file implies that it > > is related to the Harris-Foulkes and the total energy, but it is clearly > > not the trivial difference between these two quantities. > > > > Thanks in advance, > > Ben Comer > > Georgia Tech > > > > _______________________________________________ > > Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso > ) > > users mailing list users@lists.quantum-espresso.org > > https://lists.quantum-espresso.org/mailman/listinfo/users > > > > > -- > Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, > Univ. Udine, via delle Scienze 208, 33100 Udine, Italy > Phone +39-0432-558216, fax +39-0432-558222 > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://lists.quantum-espresso.org/pipermail/users/attachments/20190926/981cb548/attachment-0001.html > > > > ------------------------------ > > Message: 3 > Date: Thu, 26 Sep 2019 15:22:44 +0000 > From: Ben Comer <bcom...@gatech.edu> > To: "users@lists.quantum-espresso.org" > <users@lists.quantum-espresso.org> > Subject: Re: [QE-users] What Is Estimated SCF Accuracy > Message-ID: <ef6ec918-7a31-bda6-54d2-fb77941b3...@gatech.edu> > Content-Type: text/plain; charset="utf-8" > > Thanks this answered my question, the responses are much appreciated! > > On 9/26/19 10:58 AM, Stefano de Gironcoli wrote: > > In the simplest case it is the electrostatic self energy of the > > difference between rho_in and rho_out and as such it is an estimate of > > the energy error. in more complex cases (magnetic systems, lda+u, ...) > > it is modified in the same spirit. > > > > stefano > > > > On 26/09/19 16:51, Ben Comer wrote: > >> Hello, > >> > >> I'm trying to understand what exactly estimated SCF accuracy is. Does > >> anyone know where I can find a formal definition of what it is and how > >> it is being calculated? The structure of the output file implies that it > >> is related to the Harris-Foulkes and the total energy, but it is clearly > >> not the trivial difference between these two quantities. > >> > >> Thanks in advance, > >> Ben Comer > >> Georgia Tech > >> > >> _______________________________________________ > >> Quantum ESPRESSO is supported by MaX > >> (www.max-centre.eu/quantum-espresso) > >> users mailing list users@lists.quantum-espresso.org > >> https://lists.quantum-espresso.org/mailman/listinfo/users > > ------------------------------ > > Message: 4 > Date: Thu, 26 Sep 2019 16:02:08 +0000 > From: Eric Glen Suter <esu...@uga.edu> > To: "users@lists.quantum-espresso.org" > <users@lists.quantum-espresso.org> > Subject: [QE-users] VC-relax in polar materials > Message-ID: > < > sn4pr0201mb34227cbf8d88b6f581a9c4dbd3...@sn4pr0201mb3422.namprd02.prod.outlook.com > > > > Content-Type: text/plain; charset="iso-8859-1" > > Hello all, > > I'm attempting to apply DFT calculations to a ferroelectric phase of a > material. Are there special considerations to pay attention to when doing > structural calculations on system like this? For instance, do we expect > that a standard vc-relax will find a ferroelectric state of the material? > > I've seen some discussion on the use of the Berry phase options to > calculate the polarization of the material, but is that necessary to > include in order to get a satisfactory structure? > > Thanks in advance for any insights you can offer. > > Best regards, > > Eric Suter > > ---------------------------- > > PhD Candidate, Dept. of Physics and Astronomy > > Center for Simulational Physics > > University of Georgia > > ---------------------------- > > email: esu...@uga.edu > > phone: 912-856-3071 > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://lists.quantum-espresso.org/pipermail/users/attachments/20190926/91682b89/attachment-0001.html > > > > ------------------------------ > > Message: 5 > Date: Thu, 26 Sep 2019 13:33:34 -0400 > From: Brendan Smith <bsmit...@buffalo.edu> > To: users@lists.quantum-espresso.org > Subject: [QE-users] Convergence of Ecutwfc and Ecutrho for Doublet > Occupation Scheme > Message-ID: > <CAOnTLZTsqhvhNncFqxxHg0_YT= > 6evbza9vh4wj8rg4uljxy...@mail.gmail.com> > Content-Type: text/plain; charset="utf-8" > > Hi QE Experts, > > I have a system whose ground state is a doublet ( 1 spin up electron, in > this case ). I am using ultrasoft PPs. The system is a 3x3x3 super cell of > diamond with a single NV center. > > My strategy for converging Ecutwfc and Ecutrho follows the prescription > laid out by Stephano in previous exchanges on the forum. It involves two > steps: > > 1) Using the default Ecutrho = 4*Ecutwfc, I converge the total force of my > cell w.r.t Ecutwfc. > > 2) Then, using the converged value of Ecutho, I scale back Ecutwfc to see > how low I can get it without coming out of my tolerance window, which is > 1mRy in the total force computed using the converged parameters. > > When I make my unit cell charged (therefore a triplet ground state [2 spin > up electrons] ) - I get a great convergence. > > However, when doing step1 using my charge neutral (doublet) ground state, I > obtain the following for step 1 in the convergence procedure: > > 20.0000 0.238517 > 30.0000 0.273459 > 40.0000 0.272399 > 50.0000 0.270205 > 60.0000 0.269809 > 70.0000 0.269807 > 80.0000 0.274589 > 90.0000 0.274698 > 100.0000 0.270163 > 110.0000 0.270168 > 120.0000 0.270176 > 130.0000 0.270245 > 140.0000 0.274755 > 150.0000 0.270246 > > The left column is Ecut (Ry), the right column is Total Force (Ry/Bohr). > One can notice "spikes", for example, at Ecut = 140, and E cut = 80-90 Ry. > > Can such a thing happen for a particular difficult occupation scheme? I > suspect that I am oscillating between two solutions, and that using Ecut 50 > (therefore Ecutrho = 200 Ry) works here. Then, using Ecutrho = 200, I can > most likely get the Ecutwfc back to ~ 35 or so. > > Thank you for your time, > Best, > Brendan A. Smith > > 4th year graduate student studying computational chemistry at the State > University of New York at Buffalo > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://lists.quantum-espresso.org/pipermail/users/attachments/20190926/14cd768e/attachment-0001.html > > > > ------------------------------ > > Message: 6 > Date: Thu, 26 Sep 2019 19:43:57 +0000 > From: Ben Comer <bcom...@gatech.edu> > To: "users@lists.quantum-espresso.org" > <users@lists.quantum-espresso.org> > Subject: Re: [QE-users] What Is Estimated SCF Accuracy > Message-ID: <83376ab5-076f-7abe-ad6c-269d40a53...@gatech.edu> > Content-Type: text/plain; charset="utf-8" > > Just a quick follow up, the text seems to imply that A7 is used rather > than A6. do you know where this is defined in the source code? > > On 9/26/19 10:57 AM, Paolo Giannozzi wrote: > If I remember correctly: Eq.A6 of J.Phys.: Condens. Matter 21, 395502 > (2009) > > Paolo > > On Thu, Sep 26, 2019 at 4:52 PM Ben Comer <bcom...@gatech.edu<mailto: > bcom...@gatech.edu>> wrote: > Hello, > > I'm trying to understand what exactly estimated SCF accuracy is. Does > anyone know where I can find a formal definition of what it is and how > it is being calculated? The structure of the output file implies that it > is related to the Harris-Foulkes and the total energy, but it is clearly > not the trivial difference between these two quantities. > > Thanks in advance, > Ben Comer > Georgia Tech > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso< > http://www.max-centre.eu/quantum-espresso>) > users mailing list users@lists.quantum-espresso.org<mailto: > users@lists.quantum-espresso.org> > https://lists.quantum-espresso.org/mailman/listinfo/users > > > -- > Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, > Univ. Udine, via delle Scienze 208, 33100 Udine, Italy > Phone +39-0432-558216, fax +39-0432-558222 > > > > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso< > http://www.max-centre.eu/quantum-espresso>) > users mailing list users@lists.quantum-espresso.org<mailto: > users@lists.quantum-espresso.org> > https://lists.quantum-espresso.org/mailman/listinfo/users > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://lists.quantum-espresso.org/pipermail/users/attachments/20190926/00591978/attachment-0001.html > > > > ------------------------------ > > Message: 7 > Date: Thu, 26 Sep 2019 21:57:25 +0200 > From: Paolo Giannozzi <p.gianno...@gmail.com> > To: Quantum ESPRESSO users Forum <users@lists.quantum-espresso.org> > Subject: Re: [QE-users] What Is Estimated SCF Accuracy > Message-ID: > <CAPMgbCssnkbb= > vagor55dkugkouv8wg6wyt8u2vmrw_nctz...@mail.gmail.com> > Content-Type: text/plain; charset="utf-8" > > On Thu, Sep 26, 2019 at 9:44 PM Ben Comer <bcom...@gatech.edu> wrote: > > > Just a quick follow up, the text seems to imply that A7 is used rather > > than A6. do you know where this is defined in the source code? > > > Variable dr2 in PW/src/mix_tho.f90, routine rho_ddot in PW/src/scf_mix.f90 > > Paolo > > > On 9/26/19 10:57 AM, Paolo Giannozzi wrote: > > > > If I remember correctly: Eq.A6 of J.Phys.: Condens. Matter 21, 395502 > > (2009) > > > > Paolo > > > > On Thu, Sep 26, 2019 at 4:52 PM Ben Comer <bcom...@gatech.edu> wrote: > > > >> Hello, > >> > >> I'm trying to understand what exactly estimated SCF accuracy is. Does > >> anyone know where I can find a formal definition of what it is and how > >> it is being calculated? The structure of the output file implies that it > >> is related to the Harris-Foulkes and the total energy, but it is clearly > >> not the trivial difference between these two quantities. > >> > >> Thanks in advance, > >> Ben Comer > >> Georgia Tech > >> > >> _______________________________________________ > >> Quantum ESPRESSO is supported by MaX ( > www.max-centre.eu/quantum-espresso) > >> users mailing list users@lists.quantum-espresso.org > >> https://lists.quantum-espresso.org/mailman/listinfo/users > >> > > > > > > -- > > Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, > > Univ. Udine, via delle Scienze 208, 33100 Udine, Italy > > Phone +39-0432-558216, fax +39-0432-558222 > > > > > > _______________________________________________ > > Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso > ) > > users mailing list users@lists.quantum-espresso.orghttps:// > lists.quantum-espresso.org/mailman/listinfo/users > > > > _______________________________________________ > > Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso > ) > > users mailing list users@lists.quantum-espresso.org > > https://lists.quantum-espresso.org/mailman/listinfo/users > > > > -- > Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, > Univ. Udine, via delle Scienze 208, 33100 Udine, Italy > Phone +39-0432-558216, fax +39-0432-558222 > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://lists.quantum-espresso.org/pipermail/users/attachments/20190926/a05be498/attachment-0001.html > > > > ------------------------------ > > Message: 8 > Date: Fri, 27 Sep 2019 13:32:39 +0530 > From: Haider Abbas <haiderabbas...@gmail.com> > To: users@lists.quantum-espresso.org > Subject: [QE-users] problems in graphene simulation > Message-ID: > <CAO+nntgthf6D0wOp2fPjg=wpfrndxK9= > yrojmgezfdc47uk...@mail.gmail.com> > Content-Type: text/plain; charset="utf-8" > > Dear all, > > I am trying to simulate a modified structure of graphene. I have > successfully obtained the desired results for band-structure and the > bandgap match closely with the experimental value (2.7 eV). But I have some > problems. > > 1- when I calculate the density of states with the combination of different > k point, results are approximately the same, attached is the file. > But the main problem is that the gap does not match with the bandgap, > The density of states plot gives a gap of approx. 2 eV. > > 2- When I extract the PDOS, I have the contribution of 1S and 2P of carbon > atoms and 1 S contribution of hydrogen atoms only. > 2 S contribution of carbon is missing. > > with regards > > Haider Abbas > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://lists.quantum-espresso.org/pipermail/users/attachments/20190927/d5d6b9c5/attachment-0001.html > > > -------------- next part -------------- > A non-text attachment was scrubbed... > Name: density.pbe.pdos.pdos_tot > Type: application/octet-stream > Size: 3958 bytes > Desc: not available > URL: < > http://lists.quantum-espresso.org/pipermail/users/attachments/20190927/d5d6b9c5/attachment-0001.obj > > > > ------------------------------ > > Subject: Digest Footer > > _______________________________________________ > users mailing list > users@lists.quantum-espresso.org > https://lists.quantum-espresso.org/mailman/listinfo/users > > ------------------------------ > > End of users Digest, Vol 146, Issue 19 > ************************************** >
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