[Pw_forum] Zn NC_PP from qe-forge

[Nichols A. Romero]

The behavior here is what I might expect for a real-space DFT code,
but V_NL is evaluated in reciprocal space right (we don't have
real-space projectors)?

Just to double-check. Is charge density cutoff 4 times that planewave cutoff?

On Wed, Oct 19, 2011 at 2:51 PM, William Parker <wparker at anl.gov> wrote:
> Dear Yun Song and interested parties,
>
> The possibility of a phonon test case in ZnO piqued my curiosity so I decided to have a go at it.  I find a very odd convergence pattern with these two pseudopotentials in this system--the total energy has a damped sinusoidal decay with increasing cutoff:
> (selecting the maxima and minima at 10 Ry sampling)
>
> E_cutoff (Ry)   E_total (Ry)
> 100             -338.741
> 160             -338.660
> 210             -338.675
> 290             -338.665
> 370             -338.668
> 400             -338.667
>
> Figure here: https://wiki.alcf.anl.gov/wparker/images/b/b5/ZnO_ecut_convergence_lda_ncpp.png
> Details here: https://wiki.alcf.anl.gov/wparker/index.php/Zinc_Oxide_Parameter_Convergence
>
> I have never encountered this kind of behavior with norm-conserving pseudopotentials before.  At worst, I've seen little steps in an otherwise smooth convergence to a value.  The eigenvalues at the various k-points don't appear to have any ghost states that come and go with cutoff.  Has anyone observed this kind of oscillation in the total energy with increasing plane-wave cutoff before?  What gives rise to it?
>
> --William
>
> *********************************************************
>  William D. Parker
>  Computational Postdoctoral Fellow   fax: (630) 252-4798
>  MSD-212, Rm. C-215
>  Argonne National Laboratory
>  9700 S. Cass Ave.
>  Argonne, IL 60439
> *********************************************************
>
>
>
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>



-- 
Nichols A. Romero, Ph.D.
Argonne Leadership Computing Facility
Argonne, IL 60490
(630) 447-9793