[Pw_forum] Relaxation of AlN surface

[Gabriele Sclauzero]

On top of all other suggestions, I just want to add that it is not sage to ask for an 
energy convergence threshold (for relaxation) as strict as etot_conv_thr = 1.d-8, while 
you use only conv_thr = 1.D-6 for the self consistency threshold.
My suggestion is to choose conv_thr = 1.D-8 and leave etot_conv_thr to the default (unless 
you have some specific needing). Also consider increasing upscale from its default value.

GS

lan haiping wrote:
> Hi, Somesh ,
> How do you think about the thread for electron scf : conv_thr = 1.D-6 ?
> And only gamma k-point sampling for your cell
> seems not enough .
> 
> regards,
> 
> On Tue, Feb 17, 2009 at 6:08 AM, Somesh Kumar Bhattacharya 
> <somesh.kb at gmail.com <mailto:somesh.kb at gmail.com>> wrote:
> 
>     Dear All,
> 
>     I am a new to PWSCF.
> 
>     I am trying to relax a surface slab of AlN which has 32 atoms.
>     However, the system is not achieving convergence.
> 
>     The input file is  :
> 
>     &control
>        calculation = 'relax'
>        restart_mode='from_scratch',
>        prefix='AlN',
>        nstep = 100,
>        tprnfor = .true.,
>        etot_conv_thr = 1.d-8,
>        pseudo_dir = '~/QE/espresso-4.0.3/pseudo/',
>        outdir='.'
>     /
>      &system
>        ibrav=  4, celldm(1) = 11.71623992919922,
>        celldm(3) = 4.513,nat=32, ntyp= 2,
>        ecutwfc =30.0, ecutrho = 400, nspin =1,
>      /
>      &electrons
>        electron_maxstep=150,
>        conv_thr = 1.D-6,
>        mixing_mode = 'local-TF',
>        mixing_beta = 0.2,
>     /
>      &ions
>         ion_dynamics='bfgs',
>         phase_space = 'full'
>     /
-- 


o ------------------------------------------------ o
| Gabriele Sclauzero, PhD Student                  |
| c/o:   SISSA & CNR-INFM Democritos,              |
|        via Beirut 2-4, 34014 Trieste (Italy)     |
| email: sclauzer at sissa.it                         |
| phone: +39 040 3787 511                          |
| skype: gurlonotturno                             |
o ------------------------------------------------ o