[gmx-users] Electric double layer, how to add charge

[Andreas]

Hello users,

I want to simulate a graphene electric double layer (edl). So far i have 
used the cnt tutorials and the tutorial for lysozyme in water.
All modification to the OPLSAA field parameter (atomname2type.n2t, 
atomtypes.atp, ffbonded.itp, ffnonbonded.itp) which i have done were 
with zero charge and i could already simulate a graphite layer in a box 
filled with water and ions, similar to the lysozyme tutorial.

How and then to add a charge to the graphene layer, or if two graphene 
layers are added, how to add opposite charges to them?

Or is there a more simple way to MD simulate an edl, in gromacs, altogether?

I would be very thankful for any help

Best regards

Andreas