finite electric field calculation in 1D/2D systems

[kadants]

I would like to do finite electric field calculations
in systems with 2D and 1D periodicity with the field E
pointing perpendicular to the directions of peridicity.
I would assume the position operator is well defined
as the KS orbs vanish in the direction of the field.
Is there a possibility to add E*r in the Hamiltonian?