[Pw_forum] problem in post-processing: charge density minus superposition of atomic densities

[Paolo Giannozzi]

There is always a small but unavoidable error coming from discretization
and truncation in Fourier space. Moreover, atomic charges are computed for
the reference atomic configuration used in the pseudopotential generation,
which may differ from the neutral one.

Paolo

On Thu, Nov 3, 2016 at 1:06 PM, Duy Le <ttduyle at gmail.com> wrote:

> It should give zero or very close to zero, unless your calculation is not
> accurate or your grid is not dense enough.
>
> Duy Le
> University of Central Florida.
> On Nov 2, 2016 11:17 AM, "Uri Argaman" <argamanu at post.bgu.ac.il> wrote:
>
>> Dear QE experts
>> I do a PP calculation to get the charge density minus superposition of
>> atomic densities with the following input:
>>  &inputpp
>>     prefix  = 'ti'
>>     outdir = '/home/uriargaman/tmp8086/TMP_PLOTDELTARHO/'
>>     filplot = 'ti_delta_charge'
>>     plot_num= 9
>>  /
>>  &plot
>>     nfile = 1
>>     filepp(1) = 'ti_delta_charge'
>>     weight(1) = 1.0
>>     iflag = 3
>>     output_format = 5
>>     fileout = 'ti.delta_rho.xsf'
>>     e1(1) =1.0, e1(2)=0.0, e1(3) = 0.0,
>>     e2(1) =0.0, e2(2)=1.0, e2(3) = 0.0,
>>     e3(1) =0.0, e3(2)=0.0, e3(3) = 1.0,
>>     nx=50, ny=50, nz=50
>> The most negative value is: -0.008 and the most positive value is: 0.05.
>> In addition, the positive values do not balanced with the negative values
>> (the integral over all space is positive). Why this integral do not vanish?
>> Thank you very much
>> Uri Argaman
>> Ben-Gurion University
>> Israel
>>
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>
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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