Dear Andrii Shyichuk Thank you for this clear explanation. I remember, I did two EOS calculations: one with pseudopotential from http://physics.rutgers.edu/gbrv the other from QE website; the later did not give me a smooth curve Now thanks to you I have come to understand the reason.
By the way, is it possible to use the pseudopotential obtained from http://physics.rutgers.edu/gbrv for a calculation that includes spin-orbit-coupling? With Kind Regards On Mon, Oct 19, 2020 at 1:19 AM Andrii Shyichuk < andrii.shyic...@chem.uni.wroc.pl> wrote: > Dear Endale, > > Using values smaller than recommended might result in errors going > unpredictably high. > In your case, using e.g. 40/400 instead of 45/455 could happen to be fine > (or not), but 30/300 is most likely bad. > > In order to check it, try a few calculations with different cutoffs. As > the cutoff goes up, band gap should approach some value. > As the cutoff goes down, the point of rapid change in the values is where > things get bad. > Same goes for DOS, if it starts to change at lower cutoffs - bad. > > Another thing to check is energy-volume curve (equation of state, EOS), > which should be smooth. > If it's not - the basis is probably too low. > And, it's minimum should converge with the increasing cutoffs. > > I recommend looking into GBRV pseudopotentials (optimized for about 40 Ry > cutoff) http://dx.doi.org/10.1016/j.commatsci.2013.08.053. > > Finally, check your basis on some known materials that contain the same > elements as your material of interest. > > Best regards. > Andrii Shyichuk > > W dniu 2020-10-20 02:10, ENDALE ABEBE napisaĆ: > > Dear Expertise > > Let me say I am calculating the energy bandgap of a semiconductor, which > doesn't have reported value in literature. > What is the parameter that I need to check to say the ecutwfc/ecutrho is > sufficient and the value ot energy bandgap is correct? > > Thank you for your support > > With Best Regards > > > On Tue, Oct 13, 2020 at 1:06 AM Paolo Giannozzi <p.gianno...@gmail.com> > wrote: > >> As long as your cutoffs are sufficiently good to get the desired accuracy >> on the targeted properties, there is no problem. The cutoffs suggested in >> the PP file are on the safe side and thus quite high, if I remember >> correctly. >> >> Paolo >> >> On Mon, Oct 12, 2020 at 2:56 PM ENDALE ABEBE <end...@gmail.com> wrote: >> >>> Dear Expertise >>> >>> The suggested values of the ecutrho and ecutwfc are making my >>> calculation expensive. For instance, in the pseudo potential file of Bi, >>> Bi.pbe-dn-kjpaw_psl.1.0.0.UPF >>> <https://www.quantum-espresso.org/upf_files/Bi.pbe-dn-kjpaw_psl.1.0.0.UPF>, >>> these are: >>> >>> Suggested minimum cutoff for wavefunctions: 45. Ry >>> Suggested minimum cutoff for charge density: 455. Ry >>> >>> Is there any problem if I use less values than these as much as the >>> total energy of the system converges? >>> >>> Thank you in advance for your response. >>> >>> With Regards >>> >>> -- >>> Endale Abebe >>> Program coordinator and Lecturer >>> Faculty of Materials Science and Engineering >>> Jimma Institute of Technology >>> Jimma University >>> P.O.Box 378, Jimma, Ethiopia >>> Mobile: +251921381598 >>> _______________________________________________ >>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu) >>> 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) >> users mailing list users@lists.quantum-espresso.org >> https://lists.quantum-espresso.org/mailman/listinfo/users > > > > -- > Endale Abebe > Program coordinator and Lecturer > Faculty of Materials Science and Engineering > Jimma Institute of Technology > Jimma University > P.O.Box 378, Jimma, Ethiopia > Mobile: +251921381598 > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > 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) > users mailing list users@lists.quantum-espresso.org > https://lists.quantum-espresso.org/mailman/listinfo/users -- Endale Abebe Program coordinator and Lecturer Faculty of Materials Science and Engineering Jimma Institute of Technology Jimma University P.O.Box 378, Jimma, Ethiopia Mobile: +251921381598
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