[Pw_forum] Grimme C_ij for epitaxial graphene

[Matthieu Fortin-Deschênes]

Hi all,

I'm trying to calculate some basic properties of graphene on various  
substrates using Grimme correction for VdW interactions. The Grimme  
corrections seem to deteriorate the results (lattice parameter and  
binding energy) of the graphene as well of the substrate compared to  
experimental results.

I was wondering if it's possible to set C_ij=0 for i=j (no correction  
for C-C interactions, as well as substrate-substrate interaction), but  
non-zero C_ij for graphene-substrate interactions. As far as i know,  
C_i are defined for each element and C_ij is calculated from  
sqrt(C_i*C_j). I would like to set all C_ij by myself.

Thank you

Matthieu Fortin-Deschênes
Polytechnique Montreal