[QE-users] Calculating the total (valence + core) charge

[Alberto Otero de la Roza]

Hi Jan,

That is normal for the all-electron density. The density peaks at the
nuclei are very steep, so they are poorly represented by a uniform
grid and consequently the cube doesn't integrate to the correct number
of electrons. You can try to make the grid finer but for most systems
that won't help very much because you would need an unreasonable
number of grid points to converge it.

Best,

Alberto

--
Dr. Alberto Otero de la Roza
Department of Physical and Analytical Chemistry, 
University of Oviedo


* Jan Oliver Oelerich <jan.oliver.oelerich at physik.uni-marburg.de> [2018-10-02 11:28:05 +0200]:
> Hi QE users,
> 
> I need the total charge density (including core electrons) and calculated it
> using pp.x's `plot_num=21` method after a converged SCF calculation. (See
> below for the pw.x and pp.x input files).
> 
> Summing up the values of the `density.cube` file and multiplying the result
> with the volume element (dV=V/(96*96*180), V in bohr^3) gets me nothing even
> close to the expected value of 76 electrons. (I get 2.7..)
> 
> What am I missing here? Are my grids too small or is it something about the
> units that I got wrong?
> 
> Thanks and cheers,
> Jan Oliver Oelerich
> 
> -------pw.x----------
> &CONTROL
>     calculation = 'scf',
>     prefix     = 'GaN',
>     pseudo_dir = '/opt/QEPseudos/pslibrary.1.0.0/pbe/PSEUDOPOTENTIALS',
>     outdir     = './out',
>     wf_collect = .TRUE.,
> /
> &SYSTEM
>     ecutwfc          = 30.0
>     ntyp             = 2
>     nat              = 4
>     ibrav            = 0
>     nr1              = 96
>     nr2              = 96
>     nr3              = 180
> /
> &ELECTRONS
> /
> 
> ATOMIC_SPECIES
> Ga 69.723   Ga.pbe-dn-kjpaw_psl.1.0.0.UPF
> N  14.007   N.pbe-n-kjpaw_psl.1.0.0.UPF
> 
> K_POINTS automatic
> 6 6 4  0 0 0
> 
> CELL_PARAMETERS angstrom
> 3.18600000000000 0.00000000000000 0.00000000000000
> -1.59300000000000 2.75915693645722 0.00000000000000
> 0.00000000000000 0.00000000000000 5.18600000000000
> 
> ATOMIC_POSITIONS angstrom
> Ga 0.0000000000 0.0000000000 0.0000000000
> N 0.0000000000 1.8394379576 0.6440642113
> Ga 0.0000000000 1.8394379576 2.5930000000
> N 0.0000000000 0.0000000000 3.2370642113
> 
> 
> -------pp.x------------
> &inputpp
>     prefix  = 'GaN'
>     outdir = './out'
>     filplot = 'electron_density.dat'
>     plot_num = 21
> /
> &plot
>     nfile = 1
>     filepp(1) = 'electron_density.dat'
>     weight(1) = 1.0
>     iflag = 3
>     output_format = 6
>     fileout = 'density.cube'
> /
> 
> 
> -- 
> Dr. Jan Oliver Oelerich
> Philipps-Universität Marburg
> 
> Faculty of Physics and Material Sciences Center
> Addr.: Room 02D35, Hans-Meerwein-Straße 6, 35032 Marburg, Germany
> Phone: +49 6421 2822260
> 
> Semiconductor Theory, Department of Physics
> Addr.: Room 01001, Mainzer Gasse 33, 35032 Marburg, Germany
> Phone: +49 6421 2824335
> 
> Mail : jan.oliver.oelerich at physik.uni-marburg.de
> Web  : http://academics.oelerich.org
> 
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