C.I.=(n,m)

In addition to specifying the number of M.O.s in the active space, the number of electrons can also be defined. In C.I.=(n,m), n is the number of M.O.s in the active space, and m is the number of doubly filled (that is, not empty or partially filled) levels to be used (see Table). If OPEN(n1,n2  is present, then the number of electrons may be increased.


Table: Use of C.I.=(n,m)

Keywords

No. of M.O.s

No. of
Electrons*

C.I.=2

2

2 (1)

C.I.=(2,1)

2

2 (3)

C.I.=(3,1)

3

2 (3)

C.I.=(3,2)

3

4 (5)


* Odd electron systems given in parentheses.