[QE-users] POSCAR to QE input

[Giovanni Cantele]

Dear Poonam,

this POSCAR section
>    1.0000000000000000     
>      5.9487492159093023   -0.0000000000000000   -0.0000000000000000
>     -2.9743746079546511    5.1517679417117126    0.0000000000000000
>     -0.0000000000000000    0.0000000000000000   11.7211034581915818
means that the cell parameters are in Angstrom.
So, it can be translated into QE input directives as:
CELL_PARAMETERS { angstrom }
     5.9487492159093023   -0.0000000000000000   -0.0000000000000000
    -2.9743746079546511    5.1517679417117126    0.0000000000000000
    -0.0000000000000000    0.0000000000000000   11.7211034581915818

You can explore whether it is better to use, in place of the CELL_PARAMETERS card,
the variables designed to build up the crystal unit cell, that is, ibrav, a, b, c, cosAB, cosAC, cosBC .

As far as the atomic positions are concerned, POSCAR “Direct” means crystal coordinates,
as such you should add to the QE input file a card
ATOMIC_POSITIONS { crystal }

followed by the list of the atomic coordinates, as in the POSCAR. However, QE requires each atomic coordinate 
triplet (xat, yat, zat) be preceded by its atomic symbol. In your POSCAR the first 12 atoms are Fe, the next 12 S,
so you will have 12 lines looking like
Fe     x  y  z
and 12 lines looking like
S      x  y  z


Of course, this is the “translation” of the only POSCAR file. You then need to build up all the rest of the QE input file,
concerning the CONTROL, SYSTEM and ELECTRONS name lists, as well as the ATOMIC_SPECIES card. For these,
you might refer to the QE user guide and to the many examples included therein.

Giovanni
-- 

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
            gcantele at gmail.com
Phone: +39 081 676910
Skype contact: giocan74
Web page: https://sites.google.com/view/giovanni-cantele

> On 6 May 2020, at 07:13, Poonam Kaushik <poonamkaushik40 at gmail.com> wrote:
> 
> Dear all,
> I want to convert a POSCAR file into the QE input file. I would be very grateful if somebody helps or give suggestions.
> Fe1 S1                                  
>    1.0000000000000000     
>      5.9487492159093023   -0.0000000000000000   -0.0000000000000000
>     -2.9743746079546511    5.1517679417117126    0.0000000000000000
>     -0.0000000000000000    0.0000000000000000   11.7211034581915818
>    Fe   S 
>     12    12
> Direct
>   0.3954866316692124  0.0721204949184797  0.1217724210678790
>   0.9278795160815250  0.3233661487507409  0.1217724210678790
>   0.6766338512492591  0.6045133683307876  0.1217724210678790
>   0.3954866316692124  0.0721204949184797  0.3782275859321179
>   0.9278795160815250  0.3233661487507409  0.3782275859321179
>   0.6766338512492591  0.6045133683307876  0.3782275859321179
>   0.0721204949184797  0.3954866316692124  0.8782275859321180
>   0.3233661487507409  0.9278795160815250  0.8782275859321180
>   0.6045133683307876  0.6766338512492591  0.8782275859321180
>   0.0721204949184797  0.3954866316692124  0.6217724140678820
>   0.3233661487507409  0.9278795160815250  0.6217724140678820
>   0.6045133683307876  0.6766338512492591  0.6217724140678820
>  -0.0000000000000000 -0.0000000000000000  0.0000000000000000
>  -0.0000000000000000 -0.0000000000000000  0.5000000000000000
>   0.3333333429999996  0.6666666870000029  0.0251416953082458
>   0.3333333429999996  0.6666666870000029  0.4748582936917498
>   0.6666666870000029  0.3333333429999996  0.9748582936917498
>   0.6666666870000029  0.3333333429999996  0.5251417063082502
>   0.6643064194527374  0.9999477489745914  0.2500000000000000
>   0.0000522750254107  0.6643586704781460  0.2500000000000000
>   0.3356412995218515  0.3356935805472627  0.2500000000000000
>   0.9999477489745914  0.6643064194527374  0.7500000000000000
>   0.6643586704781460  0.0000522750254107  0.7500000000000000
>   0.3356935805472627  0.3356412995218515  0.7500000000000000
> Thanks,
> Poonam S
> 
> 
> 
> -------------------------------------------------------------------------------------------------
> Poonam Sharma
> Research Scholar 
> Department of Physics
> Indian Institute of Technology Bombay
> Mumbai - 400076
> India.
> 
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