My Community

I am calculating bilayer of graphene. I check with slab bilayer with primitive cell of 4 atoms and super cell of 144 atom.

The problem is the interlayer distance is different in two cases. I got 3.32 in case of 4 atoms in unit cell and 3.29 in case of 144 atoms.

Can you give me some advices to make two calculations are the same?

I appreciate to all your help.

Sincerely,

Duong Dinh Loc

PS: The k-points i used is 20x20x1 for the first case and 6x6x1 for the second case.

Hi,

this interaction is caused by van der Waals forces. They are not included in DFT. So what you observe is a shallow potential perpendicular to the sheets.
You'll have to have small stepwidth (POTIM) to get similar numbers.

Hth,
alex

Thanks you so much, Alex.

Sincerely,
Duong Dinh Loc