about "nel" and "Fermi_diff" parameters

[fanchem]

Dear all,

I am trying to do my calculation with screening effect included. After going through the code, I noticed there two parameter closely related to the screening effect: nel, and Fermi_diff. I have a few questions about the two parameters.

For the Fermi_diff, it is described as "Difference between Fermi energy and band edge". I am wondering the band edge is for valence or conduction band? Is the Fermi_energy read from the fine k(q) grids?
For the nel, I am really lost here. Does this parameter indicate something like carrier concentration? Or how should I choose this value?

Thank,
Fanchem

[carla.verdi]

Dear Fanchem,

The band edge is the conduction band. The Fermi energy is either calculated from the fine k grid, or provided as an input.
Nel is the number of extra electrons in your unit cell (so it's not a density, but an electron number).

Best
Carla