Hello,

I had another question related to units of electric field in VASP. A user asked the same question a couple years ago:

https://www.vasp.at/forum/viewtopic.php ... V%2F%C3%85.

However, I wasn't able to parse the moderator's answer as it seemed contradictory to me; "Because VASP is using (mostly) atomic units then q is unity. In that case, the potential V and energy Energy are in eV.

The numeric value you want is EFIELD=0.25V/Å which corresponds to EFIELD=1.60217663e-19*0.25 eV/Å."

The statement that q is unity seems to directly contradict the statement the EFIELD should be given with the charge of the electron in coulombs. (I don't understand the EFIELD=0.25V/angstrom bit, since EFIELD is explicitly in energy/length units.

So to ask again really explicitly; Does an EFIELD setting of EFIELD=1 eV/angstrom in VASP correspond to a "real" or "lab" electric field of 1 V/angstrom, OR of (1.6*10^(-19) V/angstrom?)

And to go the other way, if in my VASP potential energy, I have a potential energy drop of 1 eV, does that correspond to applying an electric field of 1 V/angstrom, or 1.6*10^-19 V/angstrom?

This is rather important to understand in order to determine whether the electric field strength as calculated for the system of interest is remotely relevant experimentally.

Thank you in advance!