[QE-users] Supercell relaxation

[Daniel Rothchild]

Hi Vishva,

As the CRASH file says, the first and second atoms in your input file
differ by exactly one lattice vector. In fact, there are several such pairs
of atoms in your input file that differ by exactly one lattice vector -- in
other words, those pairs of atoms are directly on top of each other. How
are you generating your input structure? If you're familiar with Python,
you might try using ase's structure building tools. Something like:

from ase.build import bulk, make_supercell
atoms = make_supercell(bulk("Fe"), [[2, 0, 0], [0, 2, 0], [0, 0, 2]])

This won't make the simple cubic unit cell in your original input file, but
it will make a 2x2x2 BCC supercell of Fe that you can use to write out the
cell and positions for use with quantum espresso.

Daniel Rothchild
Unaffiliated (recent UC Berkeley PhD grad)

On Mon, May 13, 2024 at 5:58 AM VISHVA JEET ANAND via users <
users at lists.quantum-espresso.org> wrote:

> Thank you for your answer.  When I put the atomic position in angstrom, I
> got a crash report that is attached here.
>
> On Mon, May 13, 2024 at 4:38 PM Giovanni Cantele <
> giovanni.cantele at spin.cnr.it> wrote:
>
>> Dear Vishva,
>>
>> before running any calculation it is a good practice to visualize your
>> input structure, because many times convergence issues derive
>> from errors in the input geometry.
>>
>> If you do so with yours, you see atoms at extremely small distances from
>> each other, which prevents pw.x from reasonably converging
>> in an acceptable number of steps.
>>
>> The second step is to understand why the structure is wrong. In your case
>> my guess is that you tell pw.x that you're providing positions in alat
>> units,
>> whereas those units are Angstrom.
>>
>> The number of atoms depends on what you want to do. If you what to use a
>> simple cubic unit cell (as in your input file) and the bcc unit cell is
>> composed by N atoms,
>> then the 1x1x1 CONVENTIONAL unit cell will contain 2N atoms. If, on top
>> of that, you want also build a 2x2x2 unit cell, than that number has to be
>> multiplied by 2x2x2.
>>
>> Giovanmi
>> --
>>
>> Giovanni Cantele, PhD
>> CNR-SPIN
>> c/o Dipartimento di Fisica
>> Universita' di Napoli "Federico II"
>> Complesso Universitario M. S. Angelo - Ed. 6
>> Via Cintia, I-80126, Napoli, Italy
>> e-mail: giovanni.cantele at spin.cnr.it <giovanni.cantele at spin.cnr.it>
>> Phone: +39 081 676910
>> Skype contact: giocan74
>>
>> ResearcherID: http://www.researcherid.com/rid/A-1951-2009
>> Web page: https://sites.google.com/view/giovanni-cantele/home
>>
>>
>> Il giorno lun 13 mag 2024 alle ore 12:08 VISHVA JEET ANAND via users <
>> users at lists.quantum-espresso.org> ha scritto:
>>
>>> Dear Users
>>> I try to run Fe (bcc) structure 2x2x2 supercell for relaxation
>>> calculation but scf does not converge in 1000 iterations. Secondally how
>>> many no. of atoms in Fe (bcc) structure. Here I attached my input file.
>>>
>>> --
>>> With Regards
>>> Vishva Jeet Anand
>>> Research Scholar
>>> Department of Chemistry
>>>
>>> _______________________________________________
>>> 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
>>
>>
>
> --
> With Regards
> Vishva Jeet Anand
> Research Scholar
> Department of Chemistry
>
> _______________________________________________
> 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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20240513/4bd99b3a/attachment.html>