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 levels to be used. Examples:

  Keywords           Number of M.O.s  No. 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)
  C.I.=(3,0) OPEN(2,3)     3             2 (N/A)
  C.I.=(3,1) OPEN(2,2)     3             4 (N/A)
  C.I.=(3,1) OPEN(1,2)     3           N/A (3)

Odd electron systems given in parentheses.