[QE-users] Output of post-processing pp.x for 1D plot of the pseudo charge density from individual orbitals

[Paolo Giannozzi]

The third column is the integral of the second one along the chosen 
path. It is useful for the radially averaged charge density. Don't know 
about the negative sign: it might be an artifact of the interpolation, 
or, for ultrasoft pseudopotentials, a case of "negative charge"

Paolo

On 15/04/2024 11:56, Marin Luca wrote:
>
> Dear QE users,
> 
> 
> I'm facing difficulties in interpreting the output of pp.x. I'm running 
> a scf calculation on an isolated atom of Xe and a subsequent 
> post-processing in order to plot the (pseudo) charge density coming from 
> the individual atomic orbitals. I am running QE v6.4.1
> 
> By reading the manual of pp.x (PP/Doc/INPUT_PP.txt), I read that it 
> should be possible to obtain a 1D plot (a simple x-y plot of a 1D 
> function) of this charge density. I tried to do so with the following 
> input file:
> 
> 
> &INPUTPP
> prefix = 'smoothy',
> outdir = './smoothy/',
> filplot = 'smoothy.dat',
> plot_num = 7,
> kpoint=1,
> kband(1) = 1,
> kband(2) = 18,
> !lsign=.true.
> /
> &PLOT
> filepp(1)= 'smoothy.dat'
> weight(1) = 1.0
> 
> iflag=0
> output_format = 0,
> 
> fileout = 'smoothy.plt'
> e1(1) = 0.5,
> e1(2) = 0.5,
> e1(3) = 0.5,
> x0(1) = 0,
> x0(2) = 0,
> x0(3) = 0,
> nx = 800
> /
> 
> in which my idea is to plot the charge density of each orbital along 
> that line defined by the vectors e1 and x0.
> 
> The calculation finishes fine, but the output "plottable" files contain 
> 3 columns (they look like this):
> 
>          0.0000000000       -0.0174697150        0.0000000000
>          0.0012515645       -0.0174697013       -0.0000000007
>          0.0025031289       -0.0174696330       -0.0000000036
>          0.0037546934       -0.0174694282       -0.0000000101
>          0.0050062578       -0.0174689508       -0.0000000216
> 
> and many other lines. While I sort of get that the first column is the 
> spatial variable and the second should be the charge density (the 
> |\psi|^2), I have no clue what the third column is.
> 
> Could anyone explain to me what the third column means and what I should 
> plot in order to get the pseudo charge density as a function of this 
> radial coordinate only? Moreover, even with lsign commented out, some 
> values of the second column are negative which is very weird as this 
> should be |\psi|^2. Do you also have an answer on this?
> 
> I thank you all in advance for your help and time!
> 
> Best wishes,
> Luca
> 
> ETH Zurich
> Luca Marin
> Materials Theory
> Department of Materials
> HIT G 43.1
> Wolfgang-Pauli-Strasse 27
> 8093 Zurich, Switzerland
> phone +41 44 633 81 67
> luca.marin at mat.ethz.ch <mailto:luca.marin at mat.ethz.ch>
> https://www.theory.mat.ethz.ch <https://www.theory.mat.ethz.ch/>
> 
> 
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 206, 33100 Udine Italy, +39-0432-558216