Calculate Workfunction from LOCPOT

[fso002]

Dear all,

 I am trying to calculate the Work function of a surface slab. For this I need the Efermi (which I have from a Vasp Calculation) and the potential ( which I can get from the LOCPOT file, LVTOT= true in VASP calculation). The problem that I have is with the 1D projector, I select the LOCPOT file from the LABFloor and use the 1D projector to obtain the potential along the C axis. However, the potential value that I get is too large (when I use the SUM option).  Here are my questions:

1- Which options should I select? Sum? Average? Through a point?
2-Should I click the "add line" tab?


I already watched the VNL youtoube tutorial on how to analyze the output files but is not very thorough in the procedures.
Any help with this subject is appreciated.

Thank you,
Fernando Soto

[Anders Blom]

Definitely you need to use "average" to get the correct number.

You click "Add line" (it's a button, not a tab...) to add a line... else you don't see anything in the plot window.

[dominique costa]

Hello, I also try to calculate the elctronic workfunction with the plane average potential for pure Aluminium, using the LOCPOT file from VASP. The value given when taking the plane average effective potential of the vacuum minus E-f (given in the OUTCAR) is 2.2 eV, which is very bad. When I open the same LOCPOT with another software, vesta and I do the same, I obtain 3.98 eV, a value in good fit with experiment. There is something not clear.
Other LOCPOT files with other interfaces give me sometimes correct and sometimes uncorrect values. Does anyone has an explanation? Thank you in advance! Dominique

[Umberto Martinez]

Hi Dominique,
can you provide the LOCPOT and OUTCAR files which gives you the 2.2 eV work function with VNL?
if they are confidential you can send an email to support@quantumwise.com.
thanks!
Umberto

[zh]

Hello, I also try to calculate the elctronic workfunction with the plane average potential for pure Aluminium, using the LOCPOT file from VASP. The value given when taking the plane average effective potential of the vacuum minus E-f (given in the OUTCAR) is 2.2 eV, which is very bad. When I open the same LOCPOT with another software, vesta and I do the same, I obtain 3.98 eV, a value in good fit with experiment. There is something not clear.
Other LOCPOT files with other interfaces give me sometimes correct and sometimes uncorrect values. Does anyone has an explanation? Thank you in advance! Dominique

If you plot the planar average potential as  a function of z (the thickness of slab) obtained by two post-processing tools, you can easily figure out the reason for the discrepancy.  It is obvious that these two post-processing tools give different values of vacuum energy level.