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.