ABINIT Discussion Forums

Dear abinit users,

I need your help. I want to compare the primitive cell band structure and supercell band strucutre of cubic BaTiO3. I have calculated unit cell band strucuture of cubic BaTiO3 using the attached primitive cell.input file. But, I don't know how to define kptbounds (M, X, R, G, M, R points) variable for supercell BaTiO3. I have also attached the supercell.input file for supercell BaTiO3.
Thanks already for your help.

Best wishes

Dear abgs01,
You have a 2x2x2 supercell such that the zone boundary points of the unit cell (with 1/2 coordinates, i.e. X, M, A, etc) are folded into Gamma point of the supercell. You have to use an unfolding method if you want to recover the right dispersion but it depends what you need, if it is the band gap then this is fine. For the kptbounds, you can keep the same but knowing that 1/2 is folded into Gamma in the supercell.
There is a code in Abinit to unfold the bands but I never used it...
You can also use an external packages to unfold such as:
https://www.ifm.liu.se/theomod/compphys/band-unfolding/
Best wishes,
Eric