Yambo Community Forum

Dear all,

Is there a away to estimate the vacuum level position of a given meterial from a gw band structure calculation?

Thanks in advance,

Karim

Dear Karim,

DIrectly from the GW band structure I would say no.
Please have a look to this post,
may be it can help you. Anyway, are you dealing with a surface (slab model)? In this case I think you should first align the DFT levels to the potential in the vacuum, next the GW will give you the quasiparticle correction.
If you are dealing with a bulk there a different recipes to align the DFT levels:see e.g this paper, note there is not a general energy reference in periodic systems.
Technical issue: please note that Yambo once has read the electronic structure from the DFT code (Pwscf or Abinit) it shift the zero energy to the homo, or VBM.
Anyway, I'm not expert on that and may be someone else can correct me and give you more information.

Best,

Daniele

Dear Daniele,

Thank you for the advice!

It works.

Best Karim

Hi Karim,

If you are using QE to carry out the DFT calculation, you can use pp.x to calculate the electrostatic potential of your system, then you can try to plot plane-averaged potential as respective to z-direction (normal to your surface), that will give you the relative position to vacuum level. Since the vacuum level is coming from Coulomb interaction, so the correction from GW method will not (?) affect it. Then you can use the vacuum level from DFT and the energy level from GW to get the relative position. This is what pops up in my mind, wish other people can give more sophisticated way to do this.

Thanks,
lesheng

rezuzu wrote:Dear all,

Is there a away to estimate the vacuum level position of a given meterial from a gw band structure calculation?

Thanks in advance,

Karim