[DFTB-Plus-User] zero of energy for two different electric field

[lida.ansari]

Hi,

I was wondering if two different electric fields is applied in a system, 
the zero of energy for these two calculation will be the same in DFTB+.

We're writing a follow up to our APL, 97, 062105.  We're using the 
Hamiltonian from DFTB+ for a self-consistent NEGF calculation.  We 
applied a gating potential in the scattering region by using point 
charges in DFTB+.  But the electrodes come from a separate DFTB+ 
calculation with no applied fields.  The supercell for the scattering 
region is too short to allow the applied potential to asymptote to 
zero.  So we find that the band structures for these two DFTB+ 
calculations have the same shape, but are shifted by a few Hartree.  Of 
course, the NEGF results are sensitive to the relative energy levels of 
the scattering region and electrodes, so we would like to know how much 
of this shift is physical.

Thanks in advance,
Lida