If the device geometry and the field distributions are one-dimensional, like it is the case for planar capacitors, a simplified model can be applied. This model takes advantage from the fact that the resulting electric field will be perpendicular to the contacts and, if an orthogonal grid is applied for discretization, to the box boundaries. If this is the case, the polarization can be calculated using the electric field strength in the direction perpendicular to the box boundary only, thus reducing the numerical effort significantly.