[QE-users] Ionic + hartree potential

[Paolo Giannozzi]

"e*V" is meant to indicate "charge times potential", as opposed to
"potential", not "electronvolt". Energies are in atomic Ry units unless
otherwise stated, so your potential (energy) in the vacuum is around 14 eV

Paolo

On Thu, Mar 25, 2021 at 2:23 PM Offermans Willem <willem.offermans at vito.be>
wrote:

> Dear Quantum Espresso friends,
>
> I have relaxed a Pt(111) surface with 5 metal layers and S_2 symmetry :)
>
> To validate the calculations, I like to plot the x,y-averaged
> electrostatic potential
> along the z-coordinate of the unit cell.
>
> I have used pp.x and the following input file (pt.ppi) to obtain the
> values for the electrostatic
> potential on a grid. Please correct me if I’m wrong, but I thought it was
> the FFT grid.
>
> pt.ppi:
> <snip>
> $inputPP
>    outdir='.'
>    plot_num=11
>    filplot = 'Pt111_5M3V2x2.estatic.pot'
> /
> </snip>
>
> As expected `pp.x < pt.ppi` yielded Pt111_5M3V2x2.estatic.pot.
>
> I then used average.x and the following input file (pt.avi) to obtain the
> x,y-averaged values
> for the electrostatic potential along the z-coordinate of the unit cell.
>
> pt.avi
> <snip>
> 1
> Pt111_5M3V2x2.estatic.pot
> 1.0
> 1440
> 3
> 3.835000000
> </snip>
>
> `average.x < pt.avi` yielded a avg.dat file.
>
> I then plotted the the first and second column of avg.dat file with
> gnuplot. The plot is attached to this e-mail.
>
> According to https://www.quantum-espresso.org/Doc/INPUT_PP.html#idm24: "
>
> All potentials have the dimension of an energy (e*V, not V).”
>
> So, the graph shows that the electrostatic potential varies between ca.
> -0.4 eV and ca. 1 eV.
> So the vacuum electrostatic potential is about 1 eV.
>
> According to the pw.x calculation, the Fermi energy is 8.2481 eV
>
> This is not consistent to my idea. I would have expected a Fermi energy
> smaller than 1 eV, or a
> vacuum electrostatic potential > 8.2481 eV.
>
> What am I doing wrong? Did I plot the electrostatic potential?
>
>
>
>
>
>
> Met vriendelijke groeten,
> Mit freundlichen Grüßen,
> With kind regards,
>
>
> Willem Offermans
> Researcher Electrocatalysis SCT
> VITO NV | Boeretang 200 | 2400 Mol
> Phone:+32(0)14335263 Mobile:+32(0)492182073
>
> Willem.Offermans at Vito.be
>
>
>
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 206, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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