some questions about spin transport

[Roc]

Dear everyone,
    I have investigated the spin transport properties of one magnetic molecule, and I got the transmission spectrum and MPSH energy spectrum under zero bias voltage, as follows,

Transmission spectrum:
Energy (eV)   Spin-Up Coefficient   Spin-Down Coefficient
.......
        -0.03                0.0100                  0.0535
        -0.02                0.0085                  0.0467
        -0.01                0.0074                  0.0416
         0.00                0.0063                  0.0390
         0.01                0.0049                  0.0237
         0.02                0.0094                  0.0520
         0.03                0.0062                  0.0296
........

# Energy Spectrum
# -----------------------------------------------------------------------------
# Spin-Up Energy (eV)  Spin-Down Energy (eV)

............
                -1.75                  -1.27
                -1.74                  -0.93
                -1.69                  -0.43
                -1.28                   0.01
                -1.17                   0.27
                -0.95                   0.33
                 0.97                  1.22
                 1.01                   1.29
                 1.39                   2.28
                 2.26                   2.61
.........................

Question 1,
      For one spin polarization system, how to calculate the equilibrium conductance? For my system, the equilibrium conductance is G0*(0.0063+0.0390),right or not?

Question 2,
     For my spin polarization system, about the MPSH energy spectrum, how to decide the HOMO-LUMO Gap? Must we discuss it in two aspects, spin-up HOMO-LUMO Gap and spin down HOMO-LUMO Gap, respectively?

Thank you very much.

[Nordland]

Regarding question number 1:
Yes, It is a matter of definition, but it would say I think your formula is the most typical used.

Regarding question number 2:
Since this is not a non-collinear spin calculation, there is not possibility of an incoming electron-wave with one spin being scattered into a outgoing electron-wave with another spin. In most common terms we say that we disregard spin-flip, and it is in almost all cases a really good approximation. Therefore the MPSH ( and the transmission spectrum ) can be seen as two decoupled "systems" with the same geometrical system, and should be treated as such, but of the some properties like the current it is the "sum" of the two decoupled system that contribute to giving the total current.

[Roc]

thank you!