[QE-users] Is there any problem if I use less ecutwfc and ecutrho than the suggested value in the pp file?

[ENDALE ABEBE]

Thank you very much

On Mon, Oct 19, 2020 at 3:56 AM Andrii Shyichuk <
andrii.shyichuk at chem.uni.wroc.pl> wrote:

> 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
>>>> <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 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)
>>> 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)
>> users mailing list users at 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 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)
> users mailing list users at 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 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
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