[Pw_forum] How can vc-relax nanosheet that will fall apart or would be bulk?

[Duy Le]

You should try to do a normal relaxation to see if your structure is
stable. Then use the relaxed one to start vc-relax.

Duy Le
University of Central Florida

On Sat, Sep 30, 2017 at 11:34 AM, khadije alvani <khadijealvani at gmail.com>
wrote:

> Dear Q-E users,
> I try to  get vc-relax with setting ( using q-e 6.1):
>
> &CONTROL
>                  calculation = 'vc-relax' ,
>                 restart_mode = 'from_scratch' ,
>                 etot_conv_thr = 1.0E-5  ,
>                forc_conv_thr = 1.0D-4 ,
>                outdir=
>                 pseudo_dir =
>                 tprnfor   = .true.
>                 tstress = .true.
>  /
>  &SYSTEM
>                         ibrav = 4,
>                    celldm(1)=7.3509958804,
>                    celldm(3)=3.8560411311,
>                      nbnd =16,
>                          nat =2,
>                         ntyp = 2,
>                      ecutwfc = 185 ,
>                      ecutrho = 740,
>  /
>  &ELECTRONS
>           conv_thr = 1.D-8 ,
>                   electron_maxstep = 5000
>                   mixing_beta = 0.7,
> /
> &IONS
>                   ion_dynamics= 'bfgs',
>                   upscale  = 100.d0,
>
>
> /
>  &CELL
>    cell_dynamics = 'bfgs' ,
>    cell_factor = 2
>   /
> ATOMIC_SPECIES
> Zn    65.380    Zn.pbe-d-hgh.UPF
> S    32.065    S.pbe-hgh.UPF
> ATOMIC_POSITIONS (angstrom)
> Zn    0.0    2.248    7.5
> S    1.9468251077    1.124    7.5
> K_POINTS {automatic}
> 8 8 1   0 0 0
>
> but when I set  'Z=7.5 ‘ and ' cell _dofree=2Dxy ‘,  the structure of the
> nano sheet fell apart and when I relax in 3 directions , Z direction is
> decreased and would be bulk structure, so the nano sheet structure will
> lose.
> Of course it has already been done with gasp,win2k,.. .
>
> I will sincerely appreciate any comment that can help me proceed with my
> calculations.
> thank you.
> with regards
> khadije alvani
> student of university of IRAN.
> tel:  +98  916 813 4896 <+98%20916%20813%204896>
>
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