Interlayer distance of bilayer graphene

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dinhloc1984 · #1 Post by **dinhloc1984** » Thu Dec 02, 2010 2:29 pm

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.

alex · #2 Post by **alex** » Thu Dec 02, 2010 3:30 pm

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

dinhloc1984 · #3 Post by **dinhloc1984** » Fri Dec 03, 2010 12:47 am

Thanks you so much, Alex.

Sincerely,
Duong Dinh Loc