How can we get the band index of the bulk?

[GJK]

Dear Dr.Anders,

Thanks for your elaborative discussion.I find here that you have given the scripts for calculating the band index of a system containing odd number of electrons in both spin dependent and spin independent states.

So how to locate the conduction band and valence band quantum number in this case of odd number of electrons in order to evaluate the Bloch States-where we are supposed to give the quantum numbers of conduction band and valence band respectively.

[Anders Blom]

Please be a bit more specific. You don't really "calculate" the band index, you specify it when e.g. computing a Bloch state, or you want to determine a particular energy in a list. So what you are looking for is a way to determine a particular index, with some property, for instance the one (for a given k-point) with the lowest positive energy (i.e. the lowest conduction band index at this k).

In order to avoid confusion if you are not used to Python programming, I would strongly recommend using the Bandstructure Analyzer in VNL and just put the mouse over the state of interest, to determine its band index.

[GJK]

Its so nice of you Dr.Anders.

Actually from the Graphene Bloch states tutorial I find that we can find the band index and thus determine the conduction and valence band.
But in a system (not the unit cell) when doing work on adsorption on graphene we get so many electrons,since we can't use the unit cell for such special cases.
If the number of electrons is even (say 200 in the system) the band index will be 100 for conduction and 99 for valence(assuming number starts from 1).
But if we have a system of odd number of electrons what will be index the conduction band and valence band???

As per your advice I have tried with the Band structure Custom analyser for GNR for locating the valence band,conduction band and energy  gap value.But the analyser is not giving and curve for the band gap and valence band maxima and conduction band minima.It's giving a dot alone.I have verified that my system is having band gap from the band structure after introducing spin polarisation.But one of the direct band gap is correct(spin up) and the spin down is showing wrong message,with no curve only dots in the figure.

Your assistance and help will be appreciated Dr.Anders.