[Pw_forum] Pw_forum Digest, Vol 63, Issue 8

[Ramesh Kumar]

Dear JISEOK KIM,

Did you check/visualize your geometry ?

The Box is too small and it is far from the Si-H system.




> I'm having a difficulty on a geometry optimization using 'vc-relax'.
> I searched forum threads and followed various suggestions but the 'Total
> force' still does not converge..
> (but the pressures seems to be converged)
>
> The job steps I've taken as follows,
>
> 1. optimized k-point and ecutwfc.
> 2. optimized lattice parameter using Murnaghan fitting.
> 3. 'relax' the geometry using the lattice constant obtained from step2,
>
> ----------------------------------------------
> &control
>   calculation     = 'relax',
>   restart_mode    = 'from_scratch',
>   prefix          = '$NAME',
>   pseudo_dir      = '$PSEUDO_DIR/',
>   outdir          = '$OUT_DIR/',
>   wf_collect      = .TRUE.
>   tstress         = .TRUE.
>   tprnfor         = .TRUE.
>   etot_conv_thr   = 1.d-7
>   forc_conv_thr   = 1.d-6
>   nstep           = 1000
> /
> &system
>   ibrav           = 0,
>   celldm(1)       = 10.3345
>   nat             = 18,
>   ntyp            = 2,
>   ecutwfc         = 80.0,
> /
> &electrons
>   diagonalization = 'cg',
>   mixing_mode     = 'plain',
>   mixing_beta     = 0.7,
>   conv_thr        = 1.0d-10,
> /
> &ions
>   ion_dynamics    = 'bfgs'
>   bfgs_ndim       = 3
> /
> ATOMIC_SPECIES
> Si 28.086  Si.pbe-rrkj.UPF
> H  1.0079  H.pbe-vbc.UPF
> CELL_PARAMETERS
>   ..........
>
      ..........

> K_POINTS automatic
> 1 1 16 0 0 0
> ----------------------------------------------
>
>
> 4. check if 'Total force' is converged -> OK.
> 5. Take the final atomic coordinates from step4.
> 6. Run 'vc-relax' as,
>
> ----------------------------------------------
> &control
>   calculation     = 'vc-relax',
>   restart_mode    = 'from_scratch',
>   prefix          = '$NAME',
>   pseudo_dir      = '$PSEUDO_DIR/',
>   outdir          = '$OUT_DIR/',
>   wf_collect      = .TRUE.
>   tstress         = .TRUE.
>   tprnfor         = .TRUE.
>   etot_conv_thr   = 1.d-6
>   forc_conv_thr   = 1.d-6
>   nstep           = 10000
> /
> &system
>   ibrav           = 0,
>   celldm(1)       = 10.3345
>   nat             = 18,
>   ntyp            = 2,
>   ecutwfc         = 80.0,
>   ecfixed         = 70.0,
>   qcutz           = 150.0,
>   q2sigma         = 4.0,
> /
> &electrons
>   diagonalization = 'cg',
>   mixing_mode     = 'plain',
>   mixing_beta     = 0.7,
>   conv_thr        = 1.0d-10,
> /
> &ions
>   ion_dynamics    = 'bfgs'
>   bfgs_ndim       = 3
> /
> &cell
>   cell_dynamics   = 'bfgs'
>   press_conv_thr  = 0.1d0
>   press           = 0.d0
>   cell_factor     = 2.d0
> /
> ATOMIC_SPECIES
> Si 28.086  Si.pbe-rrkj.UPF
> H  1.0079  H.pbe-vbc.UPF
> ---------
>
   ----------

> K_POINTS automatic
> 1 1 16 0 0 0
> ----------------------------------------------
>
>
>
-- 
*With Best Regards:

*
*CH. Ramesh Kumar
Senior Research Fellow,
Computational Chemistry Lab,
Indian Institute of Chemical Technology(IICT),*
*Tarnaka, **
Hyderabad.
*
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