[Pw_forum] a question

[Jess Kondor]

 Dear espresso community,

  I have a question. I relaxed a surface (periodic in x and y direction)
with criteria for forces 4.0d-4. I wanted to calculate a polarization via
Berry phase in x-direction, however the code (berry phase) works in parallel
only for z-direction ( I need to use a parallel version due to large number
of atoms). So, I had to exchange the axes (z-> x , x->z) for both atomic
coordinates and for cell parameters:

before:
CELL_PARAMETERS cubic
   5.65402582   0.00000000   0.00000000
   0.00000000   5.65402582   0.00000000
   0.00000000   0.00000000  30.74000000

and after:
CELL_PARAMETERS cubic
 30.74000000    0.00000000   0.00000000
   0.00000000   5.65402582   0.00000000
   0.00000000   0.00000000   5.65402582

The code found 4 symmetry operations as before. The strange thing - after
those operations I performed scf calculations with the same parameters and
output forces are huge ~ 0.02 Ry/au. So, it looks like a system is not
relaxed. Did I do something wrong?

cheers,
 jess


-- 
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Jess Kondor

PICYT, Av. Venustiano Carranza 2425-A,
San Luis Potosí 78210, México
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