Questions about F-sapt0

Dear all,

I want to study the intra-molecular interaction of a pi-coordinated Ru complex using the F-SAPT. My fragmentation is between an allyl group and the metal moiety. The allyl group is eta-3 coordinated to the metal center.

  1. In this post Problems with FISAPT for a Cobalt Complex - #6 by dgasmith
    it says " tell the code there is no link between Cp* and Co".
    How to do so?
    And if I do not play such a trick, can I still get proper fragmentation? (It appears to me that the pi orbitals likely will be localized to the allyl group)

  2. My molecule is overall neutral. But how to assign the multiplicity for each fragment? In this post, SAPT(0) Calculation for transition metal interaction - #3 by ccavender
    it says I need to specify the overall charge and multiplicity first, and then specify them for each fragments. However, if I do so, I end up with


“Fatal Error: FISAPT: Charge on A is incompatible with singlet
with the following error message:”

The attached file is my output filetest.mpi4.txt (25.5 KB)

Many thanks for your help


I think that this answer may also apply to your system. The allyl molecule in your second fragment interacts with the Ru atom in your first fragment through coordination bonds that have strong covalent character, so SAPT’s noncovalent perturbation theory doesn’t describe this interaction well. You might be able to use I-SAPT to understand the noncovalent interaction between two different ligands in the context of the metal, but you cannot use SAPT to understand the interaction between a ligand and any fragment containing the metal.