Question about electrostatic difference potential

[kaypu]

Dear QuamWise staff:

   professor Anders  told the electrostatic difference potential is the solution to the Poisson equation where on the right-hand side you have the electron difference density, which is the (total) electron density minus the density of the neutral atoms on this forum.

i don't know how to define density of the neutral atom? is it the summation of the Isolated atom?

another question, atk use electrostatic difference potential to calculate voltage drop,  it is to say that : Voltage drop= electrostatic difference potential(under bias)- electrostatic difference potential(zero bias), we can also get the voltage drop using electrostatic potential.  it means: Voltage drop= electrostatic potential(under bias)-electrostatic potential(zero bias)  am i right?

[kstokbro]

The neutral atoms density is the superposition of the atomic densities, this density only depends on the atom positions and is independent of the voltage drop. Thus,

electrostatic difference potential(under bias)- electrostatic difference potential(zero bias) = electrostatic potential(under bias)-electrostatic potential(zero bias)
                 

[kaypu]

thank you professor kstokbro