Hello,
I have a feature request, which (I think) might be quite easy to implement but useful and interesting, too.
That is: An option to have structureless electrodes (i.e. electrodes without atoms, very similar to the dielaectric/metallic regions that are already there).
Why would it be useful: Because often you want to study transport properties of some molecular structure, with as little impact from the contacts as possible. Of course this is a somewhat crude approximation. But nevertheless you do not have to worry too much about what effect comes from the electrodes and what comes from the molecule itself. Furthermore, real atomistic electrode contain very many atoms. This pushes calculations times, but sometimes, you just want to have a simple electrode, where you don't have to worry about details of the interface and so on...
How does it work (I used it before, in a self-written TB-code; and it is described for example here: DOI: 10.1103/PhysRevB.77.125420):
We describe the electrode as some sort of metallic region without any atoms. Every atom of the molecule that is inside the electrode region couples to the electrode. We assume that this coupling is very simple, governed by a hopping constant, say gamma_xy (may be element-specific, orbital-specific, and of course user defined). Then, the self energy of such an electrode takes a very simple form: It is diagonal and has the matrix elements -i*(gamma_xy)**2 on that diagonal ( i is the imaginary number; the size of that matrix depends on which and how many atoms couple to the electrodes; the gamma_xy describe the strength of the coupling between the orbitals of different atoms and the artificial electrode). Of course, this all gets most simple if one assumes, a non-selfconsistent single orbital orthogonal tight binding approach.
It can be summarized as follows: I want to set my own, user-defined lead self energy matrix, but without too much tedious hand-work (for me okay, but not for a commercial product, so I proposed the idea of the metallic electrode regions, to define that matrix in a visual and semi-automatic way).
This request is absolutely not urgent.
And there may be some more details to care about, if one wants to really implement that: e.g. non-orthogonal basis, selfconsistency possible/meaningful?, ...
