# How to choose K point for a super cell [closed]

I have been told to use VASPKIT in order to obtain the KPOINTS, but VASPKIT only works for Primitive cell and I am currently using a super cell. The super cell has a repeated primitive cell about one of the directions, the reason I am creating a super cell is because I have to create a particular Anti Ferromagnetic state for which I need to make a structure which has a particular kind of repetitions of up and down spins that is not possible to create with the primitive cell.

Now for this I tried converging the KPOINTs but I am quite confused, a paper which has worked with the exact same super cell uses a 4x4x2 k grid. But there are a lot of permutations and combinations here our of which 4x4x2 seems to have a higher energy. I believe 4x4x4 or perhaps 5x5x5 will do a better job

Furthermore, how should I choose the Kpoints for the Band structure. Originally I planned on using VASPKIT but I dont think that is a good idea anymore. I tried obtaining a k point file and the file has different k points from the one in paper.

Will the Kpoints be same for the unit cell and the super cell ? Considering that they are the high symmetry points of the Wignerâ€“Seitz, shouldn't the wigner-seitz cell remain same??

• what is your convergence tolerance criteria to stop? For me variation is quite low. and convergence doesn't mean convergence to lower energy states. it is convergence to stable energy value May 12, 2022 at 15:46
• @Pranavkumar generally speaking I think k point convergence requires us to have stable energy value only but I said that 4x4x2 has higher energy which could be another reason why we shoudl not take it. On the other hand we get similar values for all 4x4x4 or 5x5x5 or higher k points May 12, 2022 at 18:26
• Regarding the convergence, I agree with @Pranavkumar that what you need to do is to decide your convergence threshold, which will depend on what physical properties you are ultimately interested in. Regarding the relation between k-points in the primitive and supercells, you will have to transform them as the Brillouin zone of the primitive cell will be different to the Brillouin Zone of the supercell. May 16, 2022 at 7:36