[QE-users] [EXT] Help with Environ

[Andreussi, Oliviero]

Hi Sankha,

Thanks for reporting your doubts with Environ. Similarly to the potential, the Fermi energy is defined up to an additive constant which is not uniquely defined. If you introduce the dielectric, the Fermi energy changes. If you look at the value of the Fermi energy with respect to the value of the potential in the vacuum, I.e. the workfunction, and you compare it to the same quantity in solution (a.k.a. the potential of zero charge) you should expect them to be different. Having said this, the way the potential is shifted inside of Environ is probably different from a standard calculation in vacuum and depends on the pbc correction that you use. Please pay attention to the fact that in an Environ calculation there is a correction that needs to be added to the Fermi energy and is printed out in the output a few lines after the Fermi energy itself.

I hope this helps, if you have other problems or doubts, please let me know.

Regards,

Oliviero Andreussi
University of North Texas


On Mar 5, 2019, at 7:39 PM, Sankha Mukherjee <sankha.mukherjee at utoronto.ca<mailto:sankha.mukherjee at utoronto.ca>> wrote:


Hello all,



I am working on catalysis related projects using Environ. When running SCF and subsequently NSCF using Environ I have noticed a discrepancy between the values of the Fermi levels when introducing a dielectric constant >1. Considering the vacuum case, these Fermi energies are nearly identical however.



I was wondering how the permittivity of the medium could be causing this contrast, and if there is one of these values I can trust more than the other.



Thanks,

Sankha Mukherjee
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