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cceom

NAME

cceom - equation of motion coupled cluster energy program

DESCRIPTION

The program cceom calculates EOM-CCSD energies using a Davidson algorithm to solve for the right-hand eigenvectors of the CC Hamiltonian.

OPTIONS

After internal coordinates are detected or generated, optking will enter a run-time mode dependent on command line arguments.

 --dot_with_Lg    -  check the orthogonality of the excited right-hand eigenvector with
                  -  the ground state left eigenvector, lambda.  cclambda must be run
                  - first for this to work
 

REFERENCES

1.

The equation of motion coupled-cluster method. A systematic biorthogonal approach to molecular excitation energies, transition probabilities, and excited state properties, J. F. Stanton and R. J. Bartlett, J. Chem. Phys. 98, 7029 (1993).

EOM_REFERENCE = integer

specifies the algorithm used by cceom. useful for debugging. also must currently be set to ROHF, if you want to get triplet excited states from a singlet ground state. The default is whatever "REFERENCE" is.

STATES_PER_IRREP = array of integers

specifies the number of states of each irreducible representation desired. For example, in C2v symmetry, (0 2 0 0) specifies two excited states of A2 symmetry to be solved, regardless of the symmetry of the ground state.

PROP_SYM = integer

specifies the symmetry of the state that should be used to compute properties. defaults to the last irrep for which states are requested.

PROP_ROOT = integer

specifies the number of the root (within its irrep) that should be used to compute properties. defaults to the highest root requested.

EXCITATION_RANGE = excitation_range

used to generate initial guesses. the larger the value, the more initial guesses are made in the Davidson algorithm.

RESIDUAL_TOL = integer

Davidson algorithm will converge until the norm of the residual vector is less than 10^(-integer). default if 4.

EVAL_TOL = integer

Davidson algorithm will converge until the change in the excitation energy is less than 10^(-integer). default if 6.