Analytic gradients are available for CCSD, OO-CCD/VOD, CCD, and QCCD/VQCCD methods for both closed- and open-shell references (UHF and RHF only), including frozen core and/or virtual functionality. Analytic gradients are available for CCVB-SD for only closed-shell references (RHF). In addition, gradients for selected GVB models are available.
For the CCSD and OO-CCD wave functions, Q-Chem can also calculate dipole moments, (as well as XX, YY and ZZ components separately, which is useful for assigning different Rydberg states, e.g., vs. , etc.), and the values. Interface of the CCSD and (V)OO-CCD codes with the NBO 5.0 package is also available. This code is closely related to EOM-CCSD properties/gradient calculations (Section 7.8.16). Solvent models available for CCSD are described in Chapter 12.2.
Limitations: Gradients and fully relaxed properties for ROHF and non-HF (e.g., B3LYP) orbitals as well as RI approximation are not yet available.
Note: If gradients or properties are computed with frozen core/virtual, the algorithm will replace frozen orbitals to restricted. This will not affect the energies, but will change the orbital numbering in the CCMAN printout.
$molecule 0 1 H 0.000000 0.000000 -1.886789 He 0.000000 0.000000 -1.093834 F 0.000000 0.000000 0.333122 $end $rem JOBTYPE OPT METHOD CCSD BASIS aug-cc-pVDZ GEOM_OPT_TOL_GRADIENT 1 GEOM_OPT_TOL_DISPLACEMENT 1 GEOM_OPT_TOL_ENERGY 1 $end @@@ $molecule read $end $rem JOBTYPE SP METHOD CCSD BASIS aug-cc-pVDZ SCF_GUESS READ CC_REF_PROP 1 CC_FULLRESPONSE 1 $end