[QE-users] Error in scf calculation of large number of atoms

[Matic]

Dear Pooja,
> Inspite of multiplying the lattice constant by 2, I get the same error.

You have to think about what ibrav=2 means and then which supercell you 
obtain by the procedure you described in xcrysden. A small hint try 
googling: primitive vs conventional fcc crystal unit cell, for 
convenience here is the description of the ibrav parameter in QE:

https://www.quantum-espresso.org/Doc/INPUT_PW.html#idm200

Best Regards,

Matic Poberznik

-- 
Matic Poberznik
CNR-IOM, Trieste, Italy

> On Thu, 4 Mar 2021, 7:00 pm 박민규, <minkyupark at ulsan.ac.kr 
> <mailto:minkyupark at ulsan.ac.kr>> wrote:
>
>     Dear Pooja,
>
>     Try to check your structure again.
>     It does not look like a supercell,
>     because you did not change the lattice constant accordingly.
>
>     Best,
>     ==================================================
>     Minkyu Park
>     Research Institute of Basic Sciences, University of Ulsan,
>     93, Daehak-ro, Nam-gu, Ulsan, 44610 Republic of Korea
>     minkyupark at ulsan.ac.kr <mailto:minkyupark at ulsan.ac.kr>
>     +82-52-259-1473
>     ==================================================
>
>>     On 4 Mar 2021, at 6:16 PM, Pooja Vyas <poojavyas595 at gmail.com
>>     <mailto:poojavyas595 at gmail.com>> wrote:
>>
>>     All details are in input files. How do I solve this problem?
>>
>>     On Thu, Mar 4, 2021 at 2:44 PM sally issa
>>     <sally.issa1 at outlook.com <mailto:sally.issa1 at outlook.com>> wrote:
>>
>>         I have the same calcul with 128 atoms, sometimes it appears
>>         this error but I change the K mesh or the periodic condition
>>         are not good one.
>>         What you use for k point?
>>
>>>         On 4 Mar 2021, at 09:57, Pooja Vyas <poojavyas595 at gmail.com
>>>         <mailto:poojavyas595 at gmail.com>> wrote:
>>>
>>>         
>>>         Dear users,
>>>         I have an input script (scf1.in <http://scf1.in/> attached
>>>         below) of CaO with 2 atoms. It runs fine for scf calculation.
>>>         I want to compute the energy of CaO with 64 atoms. So I
>>>         opened scf1.in <http://scf1.in/> file in XCrysden so it
>>>         displayed 27 atoms and then I followed the below steps:
>>>         1) Display->Unit of repetition -> translational asymmetric unit
>>>         2) Above step reduced 27 atoms to 4 Ca and 4 O atoms
>>>         totalling 8.
>>>         3) Then I followed Modify->number of units drawn and
>>>         selected 2,2,2 in it. So, it displayed 8 atoms*(2*2*2)= 64
>>>         atoms.
>>>
>>>         I took these atomic positions and made the file scf2.in
>>>         <http://scf2.in/> attached below. But on running that script
>>>         for scf calculation, it shows me the following error:
>>>
>>>          %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>>>              task #         1
>>>              from check_atoms : error #       1
>>>              atoms #   1 and #   2 differ by lattice vector (-1, 1,
>>>         0) in crystal axis
>>>          %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>>>
>>>         The error is due to overlapping of atoms. But can anyone let
>>>         me know how I can compute the energy of 64 atoms? How do I
>>>         figure out the equivalent atomic positions which causes this
>>>         error?
>>>
>>>
>>>         <scf1.in <http://scf1.in/>>
>>>         <scf2.in <http://scf2.in/>>
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