In order to find binding energy, energy of dimer which consists of two molecules, and energy of each monomer were calculated. After I got those values, I did this subtraction: E binding = E dimer - (E monomer1 + E monomer2).
Two methods were used: RHF/MP2 and DFT/B97D (+dispersion correction for dimer). Actually, I found that E binding from B97D was hundred times higher (in kcal/mol) than MP2. I realize that I could not compare those two directly because dispersion energy was counted in. Did I miss something for binding energy calculation from E DFT-D?