Hi everyone

I want to simulate gas molecule interaction with graphene layer in material studio/CASTEP. I want to perform density functional theory (DFT) calculations with CASTEP. I want to calculate the binding energy and I/V curves in presence and absence of gas molecule. I can build graphene in MS but I can not simulate the interaction with gas molecule. Since I am new with CASTEP, I was wondering if anyone has any experience or idea about this subject.