[QE-users] Is there any problem if I use less ecutwfc and ecutrho than the suggested value in the pp file?
Andrii Shyichuk
andrii.shyichuk at chem.uni.wroc.pl
Mon Oct 19 12:55:44 CEST 2020
Dear Endale,
The GBRV paper says, "Both the AE calculations and the pseudopotential
constructions were scalar-relativistic, i.e., without spin–orbit
interactions.".
Hence, no.
You might try making your own SO PPs using GBRV input files for
Vanderbilt code, but as long as they optimized the recipes for SO-free
calculations, the result might not be good.
Best regards.
Andrii
W dniu 2020-10-20 05:12, ENDALE ABEBE napisał:
> 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.shyichuk at 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 napisał:
>
> 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.giannozzi at 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 <endtse at 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 [1], 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 [2])
> users mailing list users at 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 [2])
> users mailing list users at 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 [2])
users mailing list users at lists.quantum-espresso.org
https://lists.quantum-espresso.org/mailman/listinfo/users
_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu [2])
users mailing list users at 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 [2])
users mailing list users at lists.quantum-espresso.org
https://lists.quantum-espresso.org/mailman/listinfo/users
Links:
------
[1]
https://www.quantum-espresso.org/upf_files/Bi.pbe-dn-kjpaw_psl.1.0.0.UPF
[2] http://www.max-centre.eu
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