[Pw_forum] ecutwfc

[Axel Kohlmeyer]

On Wed, Feb 26, 2014 at 7:09 AM, raha khalili <khadije.khalili at gmail.com> wrote:
>
> Firstly, i have to say thank you very much for your helps.
> So sorry for too many questions. I changed the pseudopotentials to
> nonrelativistic, except Au: H.pz-rrkjus.UPF, ... . Therefore, my first
> ecutwfc and ectrho will be 27 and 378, respectively. I am in right way?

you seem to be new to the subject of electronic structure calculations
with a plane wave pseudopotential DFT code, thus a word of warning is
in place:
do not start with your (complex) research project right away. you
*have* to practice with (simple) materials, where the results of
calculations are known and you can gain experience how to obtain the
kind of results you are looking for. if you do this with a "new" or
"complex" system  (or one that is both), you will never know, if
something is the correct answer or the result of a typo or a
misconception or just plain wrong. working with simple problems with
know results takes away this insecurity and you can verify, if you are
doing your calculations correctly.

you should not guess and then ask a mailing list for confirmation, you
have to know by yourself based on tests. those tests, again, are much
easier to do with simple systems.

axel.

> Raha
>
>
> On Wed, Feb 26, 2014 at 2:50 PM, Bertrand SITAMTZE <siyouber at yahoo.fr>
> wrote:
>>
>> Dear Khadije,
>>
>> Usually, for US pseudopotentials, the charge density cutoff is 6 to 12
>> times the wavefunctions cutoff.
>> The final value to be considered being dictated by the hardest
>> pseudopotential in your list. For your Au pseudopotential, you should use
>> something like ecutrho=14*ecutwfc which will be CPU consuming because the
>> other pseudopotentials require less.
>> Therefore, either you use such value for ecutrho, or you search for
>> another pseudopotentials for C and Au. Whatever the case, a convergence test
>> is welcomed!
>>
>> Bertrand
>>
>> ******CURRENT ADDRESS
>> IMMM, UMR CNRS 6283
>>  Université du Maine
>> Le Mans, France
>> Tél: +33 6 67 61 52 15
>> e-mail: siyouber at yahoo.fr
>>               Bertrand.Sitamtze at univ-lemans.fr
>> ****************************************
>>
>>
>> Le Mercredi 26 février 2014 12h00, raha khalili
>> <khadije.khalili at gmail.com> a écrit :
>> Daer PW users
>>
>> I'm doing calculations on a system consist of 5 atoms. In their ultrasoft
>> pseudopotential files are suggested different minimum ecutwfc and ecutrho.
>> S: Suggested minimum cutoff for wavefunctions:  18. Ry
>>     Suggested minimum cutoff for charge density:  77. Ry
>>
>> N: Suggested minimum cutoff for wavefunctions:  39. Ry
>>     Suggested minimum cutoff for charge density: 263. Ry
>>
>> H: Suggested minimum cutoff for wavefunctions:  46. Ry
>>     Suggested minimum cutoff for charge density: 221. Ry
>>
>> C: Suggested minimum cutoff for wavefunctions:  37. Ry
>>     Suggested minimum cutoff for charge density: 317. Ry
>>
>> Au: Suggested minimum cutoff for wavefunctions:  27. Ry
>>     Suggested minimum cutoff for charge density: 391. Ry
>>
>> What is the best ecutwfc and ecutrho for such system?
>> Best Regards
>> --
>> Khadije Khalili
>> Ph.D Student of Solid-State Physics
>> Department of Physics
>> University of Mazandaran
>> Babolsar, Iran
>> kh.khalili at stu.umz.ac.ir
>>
>>
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>
>
>
> --
> Khadije Khalili
> Ph.D Student of Solid-State Physics
> Department of Physics
> University of Mazandaran
> Babolsar, Iran
> kh.khalili at stu.umz.ac.ir
>
>
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-- 
Dr. Axel Kohlmeyer  akohlmey at gmail.com  http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.