method keywords request a coupled cluster [67,422]
calculations, using double substitutions from the Hartree-Fock determinant for
CCD , or both single and double substitutions
for CCSD [68,69,70,71].
CC and QCID are synonyms for CCD.
All frozen core options are available with CCD and CCSD.
Include triple excitations non-iteratively 
(CCSD only). CCSD-T is a synonym for CCSD(T).
Used with the T option to request inclusion of triple excitations for both
the complete MP4 and to form CCSD(T).
Computes the T1
diagnostic of T. J. Lee and coworkers (CCSD
Sets the convergence calculations to 10-N
on the energy and 10-(N+2) on the wavefunction. The default is N=7
for single points and N=8 for gradients.
Specifies the maximum number of cycles for CCSD calculations.
energies and gradients for CCD and CCSD, numerical gradients for CCSD(T), and
numerical frequencies for all methods.
The Coupled Cluster energy appears in the output as follows (following
the final correlation iteration):
DE(CORR)= -.54979226D-01 E(CORR)= -.75019641794D+02
The CCSD energy is
labeled E(CORR), and the energy including the non-iterative triples contribution
is given in the final line.