[CP2K-user] [CP2K:18633] Work Function Calculation for Charged Systems:

[Lucas Lodeiro]

Hi,

About the vacuum level, when a charged system is calculated, the charges in
the slab system interacts with the replica in the "non-periodic" direction,
creating a electric field itself and making the Hartree potential non plane
in the vacuum zone... this also happens sometimes for neutral slab systems
with dipoles into the slab or on the surfaces which do not cancel each
other. In VASP there are dipoles and electric field corrections to
accomplish this task without this effect maintaining the 3D periodicity...
I guess you are using those in your VASP calculations. In CP2K AFAIK there
is dipole corrections, but do not remember if there is electric field
correction, but here there is the possibility to turn off the periodicity
of the cell in the "non-periodical" direction of the slab, maybe this is
the way you need to go.

Regards - Lucas

El vie, 7 abr 2023 a las 18:38, ling chen (<ling.chen at adelaide.edu.au>)
escribió:

> Dear Experts,
>
> I am currently working on calculating the work function of a system and
> have encountered a few challenges that I would appreciate your insights on.
>
> For the zero-charge system, my current method involves calculating the
> Hartree energy, taking the value in the vacuum region (usually a horizontal
> line, as shown in the attached figure), and subtracting the Fermi energy
> obtained from the .out file. This approach yields results that agree well
> with those obtained using VASP.
>
>  However, when dealing with charged systems, such as charge = -2, the
> Hartree energy in the vacuum region becomes a diagonal line (as shown in
> the attached figure). Using the average value and subtracting the Fermi
> energy results in a significant discrepancy compared to the VASP
> calculations. It has been suggested that I use the SCCS implicit water
> model to stabilize the vacuum energy level, which does indeed restore the
> horizontal line in the Hartree energy. However, the calculated work
> function deviates even further from the VASP results.
>
> I am unsure about the cause of this discrepancy and would like to inquire
> if you have any recommendations for calculating the work function in
> charged systems. Additionally, I have noticed that the work function
> calculation is significantly influenced by the CUTOFF and REL_CUTOFF
> parameters in MGRID. What values would you suggest to be appropriate for
> these parameters?
>
>  I would be grateful for your expertise in addressing these concerns.
> Thank you in advance for your time and assistance.
>
> Kind Regards,
>
> [image: Screenshot 2023-04-08 073641.png][image: Screenshot 2023-04-08
> 073716.png]Ling Chen
>
> --
> You received this message because you are subscribed to the Google Groups
> "cp2k" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to cp2k+unsubscribe at googlegroups.com.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/cp2k/035d2574-d796-4112-bdd7-f8e4cad2ab01n%40googlegroups.com
> <https://groups.google.com/d/msgid/cp2k/035d2574-d796-4112-bdd7-f8e4cad2ab01n%40googlegroups.com?utm_medium=email&utm_source=footer>
> .
>

-- 
You received this message because you are subscribed to the Google Groups "cp2k" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cp2k+unsubscribe at googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/cp2k/CAOFT4PJGPUdHgkqtmo_kGnJAWqDuSVVwCr1P1UYop4BNtHe0NQ%40mail.gmail.com.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20230407/e20f373a/attachment-0001.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Screenshot 2023-04-08 073641.png
Type: image/png
Size: 17572 bytes
Desc: not available
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20230407/e20f373a/attachment-0002.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Screenshot 2023-04-08 073716.png
Type: image/png
Size: 17729 bytes
Desc: not available
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20230407/e20f373a/attachment-0003.png>