PSI SAP0 Calculation -- ignore delta-HF calculations

Is there any way to just ignore the “SCF” calculation on dimer when we perform sapt0 calculation? I don’t need (delta-HF results) and also it takes a lot of time.



I don’t think it is possible to skip the dimer SCF calculation. SAPT is a perturbation theory method, and the unperturbed Hamiltonian to which the SAPT terms are added is the sum of the Fock operators for the dimer. In other words, SAPT needs the wavefunctions from all three SCF calculations (dimer and 2 monomers) in order to compute the SAPT terms. You can see this in the advanced example from the manual. Here, the dimer and monomer wavefunctions are calculated explicitly with different options, and then the three wavefunctions are passed as arguments to the SAPT routine.

Furthermore, I don’t think this would be a good idea even if it were possible. While the total SAPT interaction energies have been benchmarked and perform favorably compared to other quantum chemistry methods (see here), the individual components of the SAPT energies have not been validated. My understanding is that the Sherrill group is working on benchmarking these components. Meanwhile, the developers have indicated elsewhere on this forum that the individual components of SAPT energies should be taken as qualitative rather than quantitative estimates, especially for SAPT0. In other words, the sum of the individual SAPT0 components without the delta-HF term will be considerably less accurate than the total SAPT0 interaction energy, especially for the scaled variant sSAPT0.