CI-OK 

Description

In most cases, all or none of the members of a set of degenerate MOs should be included in the CI active space, where MOs are considered degenerate by AMPAC™ if they differ in energy by less than 1.0×10^-4 eV, or a value specified by the keyword CIGAP=n.nnnn. By default, AMPAC will abort a CI calculation in which the active space contains an incomplete set of degenerate MOs. To override this degeneracy test, specify CI-OK. Beware that allowing incomplete degenerate sets in the active space may bias certain spin states in the root selection if a particular spin multiplicity keyword is not specified. It may also corrupt geometry optimizations due to degenerate MOs switching in and out of the active space.

See Chapter 11, Configuration Interaction for a more complete discussion of AMPAC’s CI capability.

See also:

C.I., CIGAP, PROTO, FILL.