[Pw_forum] convergence issues

[Gabriele Sclauzero]

Hi Jonas

Jonas Baltrusaitis wrote:
> 
> INPUT
> 
>  &control
>     calculation='relax',
>     prefix='44tpcb_PBE_optimization',
>     pseudo_dir='/share/apps/espresso-4.0.4/pseudo/',
>     outdir='/home/jbaltrus/atom-lsda/',
>     nstep=200
>  /
>  &system
>    ibrav=12,
>    nat=38,
>    ntyp=4,
>    a=11.367,
>    b=9.749,
>    c=14.273,
>    cosab=-0.36922777,
>    ecutwfc=25.0

As a first hint I would suggest to specify ecutrho, since you're using Ultrasoft PPs, and 
test convergence of energy (or other quantities you're interested in) w.r.t. to this 
parameter (I usually choose ecutrho ~ 10*ecutwfc).

If you want to do spin polarized calculations, you need to specify nspin=2 and a non-zero 
starting magnetization for one species at least.

>  /
>  &electrons
>    mixing_beta=0.5D0,

Then maybe decrease the mixing parameter, or use another mixing (for instance, 
mixing_mode='local-TF' works well for highly inhomogeneous systems).


>    conv_thr = 1.D-8
>  /
>  &ions
> ion_dynamics = ’none’

Are you doing a relaxation or what?

>  /
> K_POINTS {automatic}
> 4 4 4 0 0 0

Do you want to study an isolated molecule? If so you don't need a k-point sampling, simply 
use

 > K_POINTS GAMMA

Regards

GS



> 
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| Gabriele Sclauzero, PhD Student                  |
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