Is Milliken Charge transfer physically correct?

[jjhskang]

Hi
 
With density matrix option, I made I(V)  claculation for a perfect Au(111) wire, which is composed of [3,4,3] layers in [left electorde, scattering region, right electrode] and each layer consits of 7 atoms.

I find that total Mulliken charge decreases from 923.99 to 923.89 when V changes from 0.1 to 0.6 Volt. I wonder if this much decrease (= 0.1) at 0.6V is physically correct or meaningless. namely, is charge transfer really involved at 0.6V from the scattering region to the electrode for this perfect Au wire?

Thanks 

[zh]

It may be thought as that the charge transfer occurs at 0.6 V, but this value is not the exact amount of transferred charge.  

[jjhskang]

Hi!

Let me ask a related question.

I made  calculations on I-V relation for Au(111) wire-molecule-Au(111) wire system, for which [L, C, R] = [6 layers of Au (111) wire, scattering region, 6 layers of Au(111) wire]. The scattering region consits of [LC, Mol, RC] = [3 layers of Au(111) wire, molecule, 4 layers of Au(111) wire]. At V = 1.0V, I calculated drho(z) = rho(z; V = 1.0) - rho(z; V = 0.0), where rho(z) is averaged over X and Y coordinates at a given z.

Define drho_L = Sum(z) drho(z)  z within L,
         drho_LC = Sum drho(z), z within LC
         drho_Mol = Sum drho(z), z within Mol
         drho_RC = Sum drho(z), z within RC
         drho_R = Sum drho(z), z within R,

I find that

drho_L < 0, drho_LC < 0, drho_Mol < 0,

while

drho_RC > 0, drho_R > 0.

This meas that electrons are transferred from L, LC, Mol to RC and R. Note that the direction of E-files is from L to R at V = 1.0Volt.

It is difficult to understand why electrons are transferred from the positive side to the negative side, not in the opposite direction !!

Can you give me an explanation for this observation??

Thanks !