Excited State Coupled Cluster Calculations

The most important keywords associated with EOM-CC calculations are:

STATES_PER_IRREP = (integer array)

Specifies the desired number of excited states per irreducible representation for both EOM-CC and CC-LR calculations. Note that the irreps in this keyword denote the final state symmetry, not the symmetry of the transition.

PRINT_SINGLES = boolean

Specifies whether information regarding the iterative solution to the single-excitation EOM-CC problem (normally used to obtain guesses for a ful EOM-CCSD calculation) will be printed.

RESIDUAL_TOL = integer

Specifies the order of magnitude cutoff used to determine the convergence of the Davidson algorithm residuals in the EOM-CC iterative procedure.

EVAL_TOL = integer

Specifies the order of magnitude cutoff used to determine the convergence of the final eigenvalues in the EOM-CC iterative procedure.

EOM_GUESS = (mixed array)

Specifies a set of single-excitation guess vectors for the EOM-CC procedure. This is especially useful for converging to difficult states. The EOM_GUESS keyword is an array, each element of which includes an occupied orbital index (in coupled cluster ordering), a virtual orbital index, a weighting factor, and a spin (0 for $\alpha$ and 1 for $\beta$). The guess vector will be normalized after it is read, so only the relative magnitudes of the weight factors are important.

JOBTYPE = string

A value of oeprop will result in the calculation of oscillator strengths, rotational strengths, and dipole moments for an RHF reference and all but the rotational strengths for an ROHF or UHF reference.