In the *CCEXCI section the input that is
specific for coupled cluster linear response calculation of
electronic excitation energies is given.
Coupled cluster linear response excitation energies
are implemented for the iterative CC models CCS, CC2, CCSD, and CC3 for
both singlet and triplet excited states.
For singlet excited states the non-iterative models CC(2)(=CIS(D)) and CCSDR(3)
are also available.
For understanding the theoretical background for some
aspects of the CC3 calculations consult also Ref.
citeChristiansen:JCP105,Hald:JCP113,Christiansen:JCP103,Hald:JCP115.
READ(LUCMD,*) OMPCCS
READ (LUCMD,*) (NCCEXCI(ISYM,1),ISYM=1,MSYM)
Give the number of states desired.
For singlet states only, one single line is required with
the number of excitation energies for each symmetry class (max. 8).
If also triplet states are desired an additional line is given in same format.
READ (LUCMD,*) (NOMINP(ISYM,1),ISYM=1,MSYM)
DO ISYM = 1, MSYM
DO IOM = 1, NOMINP(ISYM,1)
READ (LUCMD,*) IOMINP(IOM,ISYM,1),EOMINP(IOM,ISYM,1)
ENDDO
ENDDO
A way to provide an input omega for the partitioned CC3 algorithm or restrict
the self-consistent solution to specific states.
If OMEINP is not specified the program uses the best choice available to it at that
moment based on previous levels of approximations (CCSD or even better CCSDR(3))
and calculates all states as given by NCCEXC.
IOMPINP is 1 for the lowest excited state of a given symmetry, 2 for the second lowest etc.
By giving an 0.0 input excitation energy (as EOMINP) the program takes the best previous
approximation found in this run - otherwise the user can specify a qualified guess
(perhaps from a previous calculation which is now restarted).
The threshold for the solution of the excitation energies and corresponding response eigenvectors. The threshold is the norm of the residual for the eigenvalue equation. (Default: 1.0D-04).