[Pw_forum] super cell

[Vinícius Bertuzzo Lima]

Greetings!
Before anything, thank you!

I'm trying to optimize a super-cell of Pt-Sn intermetallic, but when I
determine the atomic positions of the crystal, there is overlapping of
atoms, which determine the species as the source.

For example, if I determine how the platinum atom (0,0,0), the whole basis
of the crystal will, in its vertices of platinum atoms, as my only two
intermetallic is Pt3Sn
vertices of the base would be two platinum and tin.

I understand the system, which would by ibrav = 0, but still is not working.
How would an input on which to determine the position of only two atoms of
the base and not the whole basis?

Down my input:

*&CONTROL*
*                 calculation = 'vc-relax' ,*
*                restart_mode = 'from_scratch' ,*
*                      outdir = '/home/vinicius/tmp' ,*
*                  pseudo_dir = '/home/vinicius/espresso-4.1.**3/pseudo' ,*
* /*
* &SYSTEM*
*                       ibrav = 0,*
*                   celldm(1) = 7.10082033,*
*                         nat = 5,*
*                        ntyp = 2,*
*                     ecutwfc = 30 ,*
*                     ecutrho = 300 ,*
*                 occupations = 'smearing' ,*
*                     degauss = 0.05 ,*
*                    smearing = 'methfessel-paxton' ,*
* /*
* &ELECTRONS*
*                    conv_thr = 1.D-8 ,*
*                 mixing_beta = 0.7D0 ,*
* /*
* &IONS*
*                ion_dynamics = 'bfgs' ,*
*                   bfgs_ndim = 3 ,*
* /*
* &CELL*
*               cell_dynamics = 'bfgs' ,*
*                 cell_dofree = 'xyz' ,*
* /*
*CELL_PARAMETERS cubic *
*     0.000000000    0.000000000    4.200000000 *
*     0.000000000    1.000000000    0.000000000 *
*      1.000000000    0.000000000    0.000000000 *
*ATOMIC_SPECIES*
*   Pt  195.08400  Pt.pw91-n-van.UPF *
*   Sn  118.71070  Sn.pw91-n-van.UPF *
*ATOMIC_POSITIONS alat *
*   Pt      0.000000000    0.000000000    0.000000000    0  0  0 *
*   Sn      1.000000000    0.000000000    0.000000000    0  0  0 *
*   Pt      0.500000000    0.500000000    0.707100000    0  0  0 *
*   Pt      0.500000000    0.500000000   -0.707100000    0  0  0 *
*   Sn      0.000000000    1.000000000    0.000000000    *
*K_POINTS automatic *
*  4 4 1   0 0 0 *

Thanks again. And have a great day!
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