Grimme correction and supercell

[Andrzej]

Dear users,

I performed some calculation for graphite, just for testing some
features.
Here are some results obtained from single point calculations made for
experimenrtal crystal structure under periodic conditions.
Calculations were performed for single unit cell (111), and extended
unit cells: 222, 332 and 442.

Here are values of dispersion (Grimme) energy per C atom.

111: -0.004719
222: -0.0041627
332: -0.00405803
442: -0.00405803

As the calculations were performed under periodic conditions I would
expected that all these values should be the same. Grimme correction
is purely classical expression independent of electron density,
cutoff,  lack of k-point sampling and so on.

I will be grateful for any comment.

Andrzej