[Pw_forum] Relaxed Structure: Reg

[Suresh A]

Respected Sirs/Friends,
                                I have optimised the anatase
structure(vc-relax) by default bfgs controlling parameters and with
changed  controlling parameters. Now I got two different lattice parameters
and forces as shown below.
For default values:
Total force =     0.000082     Total SCF correction =     0.000002
...................................................

CELL_PARAMETERS (alat=  6.97686888)
   1.016725684  -0.000000000   0.000000000
  -0.000000000   1.016725684   0.000000000
   0.000000000   0.000000000   2.490647736

For Changed parameters:

The changed parameters are

 &IONS

            ion_dynamics = 'bfgs' ,
            trust_radius_max = 0.2D0 ,
            trust_radius_min = 0.5D0 ,
            trust_radius_ini = 0.1D0 ,

Total force =     0.014421     Total SCF correction =     0.000014
......................................................

CELL_PARAMETERS (alat=  6.97686888)
   1.011136738   0.000000000   0.000000000
   0.000000000   1.011136738   0.000000000
   0.000000000   0.000000000   2.543455379

Which Lattice parameters I have to take for further calculations? And there
is a big difference in final force value for the structure where bfgs
controlling parameters are changed. In the input file I actually given high
convergence thresold value (conv_thr = 1.D-8) and default forc_convr_thr
values.
Is there any general procedure for doing optimization? If there please
direct me towards the solution.
                  With Regards,
A.Suresh,
Research Scholar,
Madurai Kamaraj University,
Madurai.
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