[Pw_forum] Graphene Structural Relaxation

[Gabriele Sclauzero]

In my opinion your input structure is wrong. It's very curious that it 
still looks good when visualized with xcrysden.

If you run pw.x with verbosity='high', you will get the atomic positions 
in crystal coordinates, as follows

    Crystallographic axes

      site n.     atom                  positions (cryst. coord.)
          1           C   tau(  1) = ( -0.5001249 -0.3326688  0.0000000  )
          2           C   tau(  2) = ( -0.7501874 -0.2499829  0.0000000  )
          3           C   tau(  3) = ( -0.7501874 -0.0826851  0.0000000  )
          4           C   tau(  4) = (  0.0000000 -0.3326688  0.0000000  )
          5           C   tau(  5) = ( -0.2500625 -0.2499829  0.0000000  )
          6           C   tau(  6) = ( -0.2500625 -0.0826851  0.0000000  )
          7           C   tau(  7) = ( -0.5001249  0.0000000  0.0000000  )
          8           C   tau(  8) = ( -0.5001249  0.1672981  0.0000000  )
          9           C   tau(  9) = ( -0.7501874  0.2499829  0.0000000  )
         10           C   tau( 10) = ( -0.7501874  0.4172810  0.0000000  )
         11           C   tau( 11) = (  0.5001249 -0.3326688  0.0000000  )
         12           C   tau( 12) = (  0.2500625 -0.2499829  0.0000000  )
         13           C   tau( 13) = (  0.2500625 -0.0826851  0.0000000  )
         14           C   tau( 14) = (  0.0000000  0.0000000  0.0000000  )
         15           C   tau( 15) = (  0.0000000  0.1672981  0.0000000  )
         16           C   tau( 16) = ( -0.2500625  0.2499829  0.0000000  )
         17           C   tau( 17) = ( -0.2500625  0.4172810  0.0000000  )
         18           C   tau( 18) = ( -0.5001249  0.4999669  0.0000000  )
         19           C   tau( 19) = (  0.5001249  0.0000000  0.0000000  )
         20           C   tau( 20) = (  0.5001249  0.1672981  0.0000000  )
         21           C   tau( 21) = (  0.2500625  0.2499829  0.0000000  )
         22           C   tau( 22) = (  0.2500625  0.4172810  0.0000000  )
         23           C   tau( 23) = (  0.0000000  0.4999669  0.0000000  )
         24           C   tau( 24) = (  0.5001249  0.4999669  0.0000000  )

To me it seems that some atoms are almost overlapping. For instance, the 
positions of atom 1 and atom 11 differ by a vector nearly equal to the 
first lattice vector. I think that you have included also some atoms not 
belonging to the cell centered in the orgin when building your cell. Try 
to remove the extra atoms.

HTH

GS

On 08/19/2010 11:10 AM, meysam pazoki wrote:
>
>
>
> Dear pwscf users
> Thanks for the answers.As I said,I See the honeycomb structure in 
> xcrysden.
> I dont know what is wrong, I have attached the .in file.
> Thanks  for considering my question
> Regards
> meysam Pazoki
> PhD. student of physics
> sharif university of technology
>
>
>
> _______________________________________________
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> Pw_forum at pwscf.org
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>    


-- 

Gabriele Sclauzero, EPFL SB ITP CSEA
PH H2 462, Station 3, CH-1015 Lausanne

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