In cases of problematic open-shell references, e.g., strongly
spin-contaminated doublet radicals, one may choose to use DFT orbitals, which
can yield significantly improved results.
104
Phys. Chem. Chem. Phys.
(2003),
5,
pp. 2488.
Link
This can be
achieved by first doing DFT calculation and then reading the orbitals and
turning the SCF procedure off. Note GEN_SCFMAN must be set to false
for the orbitals to be properly pseudocanonicalized.
Example 6.39 CCSD calculation of triplet methylene using B3LYP orbitals
$molecule 0 3 C H 1 CH H 1 CH 2 HCH CH = 1.07 HCH = 111.0 $end $rem EXCHANGE b3lyp BASIS cc-pvdz $end @@@ $molecule read $end $rem BASIS cc-pvdz METHOD ccsd SCF_GUESS read MAX_SCF_CYCLES 0 N_FROZEN_CORE 1 $end