Dear Paul,

Without a magnetic field, the conductance from 0 to 1 is the same as from 1 to 0.

Positive bias and negative bias do not lead to the same result if you mean by that: Ef+ev for positive bias 
and Ef-ev for negative bias.
If you provide a small script, your issue may be more clear.

I hope this helps,

On Mon, Dec 9, 2019 at 11:54 PM Paul Anderson <> wrote:
Hello, I'm trying to study a chain of molecules, say A-B-C-D, each with a unique onsite energy and hopping parameter associated to the adjacent site. Electrodes are connected in the conventional way ...-x-x-x-A-B-C-D-x-x-x....
I would like to produce an I-V curve using Landauer Formula from -1V to +1V. I would think that for negative bias, it would be correct to compute transmission probability from lead 1 to lead 0 (i.e. smatrix.transmission(0,1)) as opposed to lead 0 to lead 1 for the positive bias case. Doing so does not result in any difference in the transmission probability. However, if I reverse the sequence, I do get a different transmission spectrum. 
Shouldn't a reversed sequence result in the same transmission probability as in switching the direction of measurement lead1 to lead0? 


Abbout Adel