Keyword category:

Configuration Interaction / Spin State

ROOT=n

Description

A CI calculation can generate many CI eigenstates but only one of them, the primary CI eigenstate, is followed in a series of geometry changes such as in a geometry optimization, reaction path calculation, etc. By default, the lowest energy eigenstate (ROOT=1) having the specified spin multiplicity (or any multiplicity if no spin multiplicity is specified) is the primary CI eigenstate. Using ROOT=n, the nth lowest CI eigenstate having the specified spin multiplicity (or any multiplicity if no spin multiplicity is specified) will be used as the primary CI eigenstate. See Chapter 10, Configuration Interaction for a more complete discussion of AMPAC's CI capability.

See also:

C.I., CISTATE, SINGLET, DOUBLET, TRIPLET, etc.