[Pw_forum] Problem with constraining an atomic position

[Mahmoud Payami]

Hi again,
To be specific, I include the in and out files:
--------------------------------------------
 &CONTROL
                 calculation = 'relax' ,
                restart_mode = 'from_scratch' ,
                      outdir = '/tmp/' ,
                  pseudo_dir = './' ,
                      prefix = 'al' ,
               forc_conv_thr = 1.d-4 ,
!                     tstress = .true. ,
!                     tprnfor = .true. ,
 /
 &SYSTEM
                       ibrav = 6,
                           A = 0.28567113959937E+01 ,
                           B = 0.28567113959937E+01 ,
                           C = 32.3200000000000 ,
                         nat = 10,
                        ntyp = 1 ,
                     ecutwfc = 70.0 ,
                     ecutrho = 200.0 ,
                 occupations = 'smearing' ,
                     degauss = 0.05 ,
                    smearing = 'methfessel-paxton' ,
 /
 &ELECTRONS
            electron_maxstep = 200,
                    conv_thr = 1.d-7 ,
                 mixing_beta = 0.3 ,
                 mixing_ndim = 5,
 /
 &IONS
  bfgs_ndim         = 3,
 /
ATOMIC_SPECIES
   Al   1.0  Al.pz-vbc.UPF
ATOMIC_POSITIONS angstrom
 Al  0.000000000000000E+000  0.000000000000000E+000  0.000000000000000E+000 
0  0  0
 Al   1.42835569799683        1.42835569799683        2.02000000000000
 Al  0.000000000000000E+000  0.000000000000000E+000   4.04000000000000
 Al   1.42835569799683        1.42835569799683        6.06000000000000
 Al  0.000000000000000E+000  0.000000000000000E+000   8.08000000000000
 Al   1.42835569799683        1.42835569799683        10.1000000000000
 Al  0.000000000000000E+000  0.000000000000000E+000   12.1200000000000
 Al   1.42835569799683        1.42835569799683        14.1400000000000
 Al  0.000000000000000E+000  0.000000000000000E+000   16.1600000000000
 Al   1.42835569799683        1.42835569799683        18.1800000000000
K_POINTS automatic
  10 10 1   1 1 1
-------------------------------------

output:

    convergence has been achieved in  14 iterations

     Forces acting on atoms (Ry/au):

     atom   1 type  1   force =     0.00000000    0.00000000    0.00006914
     atom   2 type  1   force =     0.00000000    0.00000000   -0.00007622
     atom   3 type  1   force =     0.00000000    0.00000000   -0.00000979
     atom   4 type  1   force =     0.00000000    0.00000000    0.00000932
     atom   5 type  1   force =     0.00000000    0.00000000    0.00004949
     atom   6 type  1   force =     0.00000000    0.00000000   -0.00004534
     atom   7 type  1   force =     0.00000000    0.00000000   -0.00001505
     atom   8 type  1   force =     0.00000000    0.00000000    0.00001078
     atom   9 type  1   force =     0.00000000    0.00000000    0.00007297
     atom  10 type  1   force =     0.00000000    0.00000000   -0.00006530

     Total force =     0.000159     Total SCF correction =     0.000092
     SCF correction compared to forces is too large, reduce conv_thr

     bfgs converged in  16 scf cycles and  13 bfgs steps
     (criteria: energy < 0.10E-03, force < 0.10E-03)

     End of BFGS Geometry Optimization

     Final energy   =     -41.8150228286 Ry
Begin final coordinates

ATOMIC_POSITIONS (angstrom)
Al       0.000000000   0.000000000   0.355841193
Al       1.428355698   1.428355698   2.318583884
Al       0.000000000   0.000000000   4.250222911
Al       1.428355698   1.428355698   6.193971098
Al       0.000000000   0.000000000   8.120043965
Al       1.428355698   1.428355698  10.059962875
Al       0.000000000   0.000000000  11.986071843
Al       1.428355698   1.428355698  13.929789648
Al       0.000000000   0.000000000  15.861401102
Al       1.428355698   1.428355698  17.824111471
End final coordinates



Best regards,
mahmoud




> Hi All,
>
> I have performed a simple "relax" job for a few-layered Al slab. The input
> file is similar to that in example03 but with an un(?)important difference
> that all z-coordinates are positive, starting from z=0.0 for the first
> layer:
>
> Al  0.00000   0.0000000   0.0000000    0   0    0
>
> I have also constrined this z=0 atom to stay at that position during the
> relaxation. But, at the end all atoms (including the first one) are moved 
> in
> the positive z direction. How can I handle it?
> Best regards,
> Mahmoud Payami, AEOI, Tehran, Iran
>
>
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