The Psi4 manual for SAPT calculations states the following:
“For heavier elements ( i.e. , second-row and beyond), the RI auxiliary basis is unsound for this role (insufficiently flexible).”
Is there some paper, where this issue is further discussed, so that I could see how it influences the results of DF-SAPT2+3 compared to SAPT2+3?
I saw a paper regarding DF-MP2 with Dunning basis sets and in that case the RI was shown to introduce negligible errors compared to the errors due to the choice of basis set . So I am wondering why in the case of SAPT RI is a problem.
 F. Weigend, A. Köhn, C. Hättig, Efficient use of the correlation consistent basis sets in resolution of the identity MP2 calculations, J. Chem. Phys. 116 (2002) 3175–3183. doi:10.1063/1.1445115.