[QE-users] changing cell size 1x1 to 3x3 does not provide same DOS & BS

[wenusaras]

On 2024-02-24 20:43, wenusaras wrote:
> On 2024-02-24 02:00, Lorenzo Paulatto wrote:
>> Dear Wenusara,
>> 
>> the 3x3 supercell has a much larger amount of vacuum, this is a
>> typical source of problems with graphene, as one electron may like to
>> wonder out in the vacuum.  Sticking to 5-10Å of vacuum is enough and
>> should work fine, i.e. when you multiply celldm(1) by 3, you should
>> also divide celldm(3) by the same amount to keep vacuum constant.
>> Also, your plane wave cutoff seems a bit low, I assume you have tested
>> convergence properly.
>> 
>> kind regards
>> On 23/02/2024 17:48, wenusaras wrote:
>> 
>>> hi,
>>> 
>>> I am new to QE.
>>> I start with the simple pw scf code of graphene 1x1 unit cell (i.e.
>>> nat=2) then the DOS and BS was obtained.
>>> After that pw scf code was changed to 3x3 cell (i.e. nat =18) then
>>> the obtained DOS and BS was not similar to 1x1 (changing the number
>>> of kpoints was not make two BS (or DOS) similar).
>>> 
>>> Herewith I have attached the both pw scf & nscf files.
>>> 
>>> I am curious to know what is the reason for this?
>>> Is there a way to make this both DOS and BS for both 1x1 and 3x3 to
>>> similar?
>>> 
>>> _______________________________________________
>>> The Quantum ESPRESSO community stands by the Ukrainian
>>> people and expresses its concerns about the devastating
>>> effects that the Russian military offensive has on their
>>> country and on the free and peaceful scientific, cultural,
>>> and economic cooperation amongst peoples
>>> _______________________________________________
>>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu [1])
>>> users mailing list users at lists.quantum-espresso.org
>>> https://lists.quantum-espresso.org/mailman/listinfo/users
>> 
>> --
>> Dr. Lorenzo Paulatto
>> IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université
>> phone: +33 (0)1 442 79822 / skype: paulatz
>> http://www.impmc.upmc.fr/~paulatto/ - https://anharmonic.github.io/
>> 23-24/423 B115, 4 place Jussieu 75252 Paris CX 05
>> 
>> Links:
>> ------
>> [1] http://www.max-centre.eu
>> _______________________________________________
>> The Quantum ESPRESSO community stands by the Ukrainian
>> people and expresses its concerns about the devastating
>> effects that the Russian military offensive has on their
>> country and on the free and peaceful scientific, cultural,
>> and economic cooperation amongst peoples
>> _______________________________________________
>> 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
> 
> ____________________________________________________________________________________________________________
> 
> Dear Dr.Lorenzo,
> 
> Thank you very much for your explanatory suggestions.
> As you pointed out, of course there was a bit convergence issue in
> both 1x1 & 3x3 systems.
> After correcting ecutwfc and maintaining a same amount to keep vacuum
> constant (i.e.,30A for 1x1 system and 10A for 3x3 syetem), the
> resulting DOS was reasonably same for both systems.
> Feel free to comment.
> Not only that, for the both cases the equal fermi energy was obtained.
> 
> Then the Band Structures were obtained for the both systems.
> It would be a great if you could provide suggestions on, how to obtain
> more similar Band Structures for 1x1 & 3x3 systems?
> 
> Thank you for being helpful during my learning curve of QE computing.
> _______________________________________________
> The Quantum ESPRESSO community stands by the Ukrainian
> people and expresses its concerns about the devastating
> effects that the Russian military offensive has on their
> country and on the free and peaceful scientific, cultural,
> and economic cooperation amongst peoples
> _______________________________________________
> 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
______________________________________________________________________________________________
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Hi

I have attached the pngs of obtained sphegatti via the link fallowing.

https://drive.google.com/drive/folders/1pMbB8ymyWsuRpf4xOc-rFD4mYL_BHoIK?usp=drive_link

I truly appreciate your kind reviewing of the images in the link; it's 
incredibly beneficial to me.

-- 
Thank You
Wenusara Satheekshana