By default, the perturbative CABS singles correction as described in J. Chem. Phys. 127, 221106 (2007) and J. Chem. Phys. 128, 154103 (2008) is included in the reference energy of all MP2-F12 and CCSD-F12 calculations (closed and open-shell, except for LMP2-F12/3*A(loc), which is done with a different program). The corrected reference energy is stored in variable ENERGR, so that ENERGY-ENERGR are the total correlation energies. For the setting of other variables by the F12 programs see section 35.12.
The singles correction can be turned off by option SINGLES=0, e.g.
The contribution of core orbitals to the singles energy is not included by default, but can be turned on by option CORE_SINGLES, e.g.
However, we do not recommended the use of core singles, because they depend sensitively on the CABS basis construction and do not offer significant improvements in relative energies.