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

[Jan Oliver Oelerich]

Hi Alberto,

Thank you for the quick reply!

What you say makes sense, but doesn't it render the plot_num=21 feature 
kind of useless then?

BTW, using the plot_num=0 for the pseudo charge density also doesn't 
give me reasonable results, possibly for the same reason. I guess I need 
finer grids even for that case?

Ultimately I am interested in the total charge density of my system 
(including positive charges from the cores); Am I correct that this is 
difficult to obtain using QE?

Cheers!


On 10/2/18 11:37 AM, Alberto Otero de la Roza wrote:
> 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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-- 
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