VASPKIT / Discussion / VASPKIT Users: Work function energy higher than the vacuum energy (Fermi energy ~ -0.11 eV)

Reynaldo Pu - 2025-11-17

Hello everyone,

I calculated the DOS and work function of a slab model, and extracted their data using VASPKIT (tasks 111, 116, and 426 (with direction 3 (c) being the direction of the vacuum). At the moment I am trying to figure out why I am getting a negative Fermi energy. I also used FERMI = MIDGAP to ensure that the Fermi level stays in the middle of the band gap.

I'd like to know what possible mistakes could be the cause of this unphysical results. Other than the Fermi energy, the band gap and DOS seems to be alright, and the planar potentials also show no inclines in the vacuum region. I am using a symmetrical slab with dipole corrections to ensure this.

Please let me know if there are any other information I should provide to ease the troubleshooting of this problem. I have attached the INCAR file down below. Thank you!

Reynaldo

Last edit: Reynaldo Pu 2025-11-17

INCAR

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- DENNIS BOAKYE - 2025-11-17
  
  The FERMi energy is already shifted by default.
  
  On Mon, Nov 17, 2025 at 2:37 PM Reynaldo Pu reyputr@users.sourceforge.net
  wrote:
  
  Hello everyone,
  
  I calculated the DOS and work function of a slab model, and extracted
  their data using VASPKIT. At the moment I am trying to figure out why I am
  getting a negative Fermi energy. I also used FERMI = MIDGAP to ensure that
  the Fermi level stays in the middle of the band gap.
  
  I'd like to know what possible mistakes could be the cause of this
  unphysical results. Other than the Fermi energy, the band gap and DOS seems
  to be alright, and the planar potentials also show no inclines in the
  vacuum region. I am using a symmetrical slab with dipole corrections to
  ensure this.
  
  Please let me know if there are any other information I should provide to
  ease the troubleshooting of this problem. I have attached the INCAR file
  down below. Thank you!
  
  Reynaldo
  
  Work function energy higher than the vacuum energy (Fermi energy ~ -0.11
  eV)
  https://sourceforge.net/p/vaspkit/discussion/users/thread/2874f7c4ff/?limit=25#0bbc
  
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  - Reynaldo Pu - 2025-11-17
    
    Hello,
    
    Thank you for your response. Could you elaborate on this? Which tool already shifts the Fermi energy? Does this mean that EFERMI = MIDGAP is not necessary?
    
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    - DENNIS BOAKYE - 2025-11-18
      
      I thought you said you're using vaspkit? And it automatically s shifts the
      FERMi level to zero.
      
      On Mon, Nov 17, 2025 at 3:34 PM Reynaldo Pu reyputr@users.sourceforge.net
      wrote:
      
      Hello,
      
      Thank you for your response. Could you elaborate on this? Which tool
      already shifts the Fermi energy? Does this mean that EFERMI = MIDGAP is not
      necessary?
      
      Work function energy higher than the vacuum energy (Fermi energy ~ -0.11
      eV)
      https://sourceforge.net/p/vaspkit/discussion/users/thread/2874f7c4ff/?limit=25#0bbc/f3fb/cce4
      
      Sent from sourceforge.net because you indicated interest in
      https://sourceforge.net/p/vaspkit/discussion/users/
      
      To unsubscribe from further messages, please visit
      https://sourceforge.net/auth/subscriptions/
      
      alternate
      
      If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
      
      Anonymous
      
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Work function energy higher than the vacuum energy (Fermi energy ~ -0.11 eV)

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Work function energy higher than the vacuum energy (Fermi energy ~ -0.11 eV)

Reynaldo

Work function energy higher than the vacuum energy (Fermi energy ~ -0.11 eV)

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Reynaldo

Work function energy higher than the vacuum energy (Fermi energy ~ -0.11 eV)