Q. Is it possible to calculate the bond energies, A-B → A + B (A, B: radical) using the SAC/SAC-CI method with the following procedure?

1) The SAC calculation for the closed shell molecule A-B

2) The SAC-CI calculations for the radicals A and B

3) (Bond energy) = (SAC-CI energy of A) + (SAC-CI energy of B) – (SAC energy of A-B).

 

A. The calculation is possible in principle. The results would be reliable if the keywords “NolinkedSelection” and “NoUnlinkedSelection” are used. We do not recommend such calculations, because of the computational cost. Instead, we suggest considering whether the GSUM method is applicable to your system.