[Pw_forum] pbe with norm conserving pp convergence problem

[Peng Chen]

Dear Dr.  Giannozzi,

Thanks for your reply. I use smearing for computing the band structure in
afm and fm states. It looks there is still a lot to learn. If I use
occupation=fixed to calculate afm/fm states, shall I just set
tot_magnetization=0 or 1?

If I didn't set ecutrho, the default value of ecutrho is 4*ecutwfc. So the
results are the same as the following, and the energy doesn't
decrease monotonically. I tried to decrease degauss to 0.005 Ry, I got the
similar results. What I can do to make the energy converge?

ecutrho=4*ecutwfc
ecutwfc     energy            total force
30 -1086.672528 1.335253
40 -1119.972723 0.690327
50 -1129.973333 0.690484
60 -1134.622157 0.640747
70 -1136.892534 0.617201
*80 -1137.666471 0.616635*
90 -1137.620919 0.610216
100 -1137.238099 0.615361
110 -1136.89911         0.62063
120 -1136.866006 0.622763

On Mon, Sep 10, 2012 at 3:45 PM, Paolo Giannozzi <giannozz at democritos.it>wrote:

>
> On Sep 10, 2012, at 16:35 , Peng Chen wrote:
>
> > I tried to calculate an insulator Ni3V2O3 using pbe norm conserving
> > pp from pslibrary. But the energy related with ecutwfc is not
> > converged. It reaches minimum at ecutwfc=80 Ry. But when I fix
> > ecutrho=320 Ry and increase  ecutwfc, it starts to decrease
> > monotonically. I am not sure if the system reaches the convergence
> > at ecutwfc=80 Ry.
> > (smearing=mv, Degauss=0.01 Ry and kpoints = 4 4 3)
>
> if it is an insulator, why are you using smearing? Apart from this:
> with norm-conserving PP, ecutwfc is the only parameter defining
> the basis set. You should not set ecutrho.
>
> P.
> ---
> Paolo Giannozzi, Dept of Chemistry&Physics&Environment,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
>
>
>
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-- 
  Best Regards.
        Peng
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