[Pw_forum] pp.x charge density output is missing electrons

[Lorenzo Paulatto]

On 02/15/2018 05:08 PM, Dan Gil wrote:
> I have a charge density output from pp.x made in *.xsf format. I 
> integrated the total charge, but I am missing electrons.


Not a good idea, because the xcrysden grid format include the points on 
the cell surfaces twice, see 
<http://www.xcrysden.org/doc/XSF.html#__toc__11>

My guess is that you have both the wrong points and the wrong volume 
element and that they somehow almost compensate.


kind regards

> 
> I tried different integration methods: A regular sum yields 451.8 out of 
> 456 electrons, trapezoidal integration yields 447.7/456. Simpson's 
> method yields 448.4/456.
> 
> pp.in <http://pp.in>:
> -----
>   &INPUTPP
>                        outdir = 'bulkQuartz' ,
>                       filplot = 'filplot' ,
>                      plot_num = 0,
>   /
>   &PLOT
>                         nfile = 1 ,
>                     weight(1) = 1.0,
>                         iflag = 3,
>                 output_format = 5,
>                       fileout = 'fileout.xsf'
>   /
> -----
> 
> Excerpt from pw.out:
> -----
> bravais-lattice index     =            4
>       lattice parameter (alat)  =      19.1740  a.u.
>       unit-cell volume          =   67152.3918 (a.u.)^3
>       number of atoms/cell      =           99
>       number of atomic types    =            3
>       number of electrons       =       456.00
> -----
> 
> 
> Best Regards,
> 
> Dan Gil
> PhD Student
> Case Western Reserve University
> Department of Chemical and Biomolecular Engineering
> 
> 
> 
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-- 
Lorenzo Paulatto - Paris