ABINIT Discussion Forums

Dear Professor:

I know that this question will be trivial, but I don't know how to approach it:

I want to optimize several crystal structures containing Ti (4 valence electrons) and Pt (10 valence electrons). I am changing the atoms from 16 to 80. How can I calculate the number of bands (nband) appropriate to begin an optimization?

I hope you can help me.

Sincerely,
Karem

Hi

You need to count the total number of valence electrons in the system, then you divide by 2 and you have the number of occupied bands. You then add extra bands for empty states. If your system is an insulator, a dozen empty bands should be enough. If it is a metal, you'll need a bit more.

In any case, just run the calculation and check the band occupancies at the end of the calculation. If you don't have a few empty bands, then you'll need to increase nbands.

Boris