Note that some authors consider δE HF to be part of the definition of SAPT0, 28 but others do not; in the present work, we take δE HF to be an additional correction. Strictly speaking, the model defined in Eq. (11) does not simply add δE HF to the model in Eq. ( ), due to the replacement of the second-order induction amplitudes with their response analogues. However, it is common to refer to Eq. ( ) as "SAPT0 + δHF" and we shall do so.