[QE-users] Supercell relaxation

[Giovanni Cantele]

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
>
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