# Number of KPOINTS in irreducible part of Brillouin zone

I want to investigate the comparison of Total Energy per cell with respect to the number of KPOINTS in the irreducible part of the Brillouin zone but I do not know how to calculate the number of KPOINTS with grid size for e.g 3* 3 *3 what will be no. of KPOINTS for even or odd no. of k-mesh?

Thanks for the help!

It is not necessary to care about the total energy versus the number of k points in irreducible reciprocal space, which is closely related to the symmetry of the investigated structure. Of course, you can always read it from IBZKPT with a self-consistent run or any other run using VASP. Also, the printed number in IBZKPT is related to the ISYM tag.

I assume what you really care about is the total energy versus k-sampling. About the convergence tests with VASP, namely total energy versus cut-off energy and also versus k-sampling, I strongly suggest you to take a look at this tutorial: https://dannyvanpoucke.be/vasp-tutor-convergence-testing-en/

Hope it helps.

• Thanks for answer . I am following this tutorial for total energy vs k -sampling here no of kpoints in irreducible Brillouin zone has been plotted with respect to total energy but I really do not know how to calculate no .of kpoints for particular grid size to do convergence tests ? – Shalini Feb 27 at 14:03
• You can find it in IBZKPT, which is the standard output of VASP. – Jack Feb 27 at 14:45
• Thank you so much yes I found in IBZKPT and many thanks for clearing my doubts . – Shalini Feb 27 at 17:59