It is worth noting that some EDA schemes choose to orthogonalize the molecular orbitals and construct an antisymmetric Slater determinant |ψ A 0 ψ B 0 , prior to computing electrostatic interactions. This differs from the direct-product |ψ A 0 |ψ B 0 that is used in SAPT. In the former case, where electrostatic interactions are computed using an antisymmetrized reference state, the antisymmetrized electrostatics should be compared to E elst + E exch from SAPT. For Ar 2 , Fig. 23(a) shows that this sum is also repulsive, as the Pauli repulsion (E exch ) more than compensates for the attractiveness of E elst .