23.6.1 Parameters for EOM-CCSD (EOMPAR)

Normally, no further input is needed. However, some defaults can be changed using the EOMPAR directive:

EOMPAR, key1=value1, key2=value2,...

where the following keywords key are possible:

MAXDAV=nv

Maximum value of expansion vectors per state in Davidson procedure (default 10).

INISINGL=ns

Number of singly excited configurations to be included in initial Hamiltonian (default 20; the configurations are ordered according to their energy)

INIDOUBL=nd

Number of doubly excited configurations to be included in initial Hamiltonian (default 10)

INIMAX=nmax

Maximum number of excited configurations to be included in initial Hamiltonian. By default, $nmax=ns+nd$.

MAXITER=itmax

Maximum number of iterations in eom-ccsd (default 20).

MAXEXTRA=maxex

Maximum number of extra configurations allowed to be included in initial Hamiltonian (default 0). In the case of near degeneracy it is better to include a few extra configurations to avoid a slow convergence.

INIMAX is used only if INISINGL and INIDOUBL are both zero.

All keywords can be abbreviated by at least four characters.