[QE-users] k-path along non-conventional points

[Filippo Monti]

Dear all,
my name is Filippo Monti and I am a researcher at the National Research Council of Italy.
I am a physical chemist and I am a beginner in Quantum Espresso (and in DFT for solid-state materials), so I am looking for your suggestions for a problem I am facing. I have just a question, but it would ideally require both a conceptual and an operational answer.

I would like to calculate a band diagram of an organic semiconductor crystal (triclinic, P-1 space group) obtained by a pi-staking of planar aromatic organic molecules. The molecular staking is not along any particular crystal axis, since all molecules are parallel to the lattice-plane family with approx (0.5, 0.2, 0.4) Miller index.

I have the feeling that, apart from the standard high-symmetry paths, it would be interesting to investigate how bands run along the less conventional path in the direction indicated by the (0.5, 0.2, 0.4) vector in the reciprocal space. Indeed, since the molecules stack in dimers, probably some pi bands will run up and other in the opposite direction depending on their bonding or anti-bonding nature in the dimer. Does this make sense to you? …or is it completely a non-sense?

If it is a good idea, is there a direct way to find the point n*(0.5, 0.2, 0.4) crossing the border (I guess a face) of the Brillouin zone, so to define the all the points along the path form gamma (0.0, 0.0, 0.0) to that point in the reciprocal space in a quick way? I am thinking about XCrySDen or an equivalent software… or do I have to proceed from scratch?

Thanks in advance for your suggestions.

Regards,
Filippo