Ah! Thank you. Ok, the form will be something like this (for a uniform
electrical field of +0.5 eV/angs along the Z direction), but I'm still
not sure how to interpret the FUNCTION keyword and if I'm getting this
right. Any ideas?
&EXTERNAL_POTENTIAL
FUNCTION (A/B)*Z
PARAMETERS A B
VALUES [eV] 5.0 [angstrom] 10.0
&END