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 can be changed.
Table:
Use of C.I.=(n,m)|
Keywords |
No. of M.O.s |
No. of |
|
C.I.=(2,1) |
2 |
2 (3) |
|
C.I.=(3,1) |
3 |
2 (3) |
|
C.I.=(3,2) |
3 |
4 (5) |
* Number of electrons in odd electron systems given in parentheses.
See also: OPEN(n1,n2), C.I.=(n1,n2), CIS, CISD, PECI, CISDT, MECI, ROOT, MICROS, STATES ARISING, SINGLET, DOUBLET, etc.