Density functional calculations with lattice relaxation of field emitted currents

The VASP DFT package simulates external electric field by inserting the material in the middle of a charged plane capacitor under periodic boundary conditions. At self-consistency some slight electronic charge must rest at the positive capacitor plate. By subtracting its induced potential between the surface and the positive plate, a corrected total external potential is obtained, determining a corrected tunneling length and barrier height.