TABLE IV.
Occupations of the ORMAS orbital subspaces in the reference space and the excitation spaces for the four CI wave functions in which the 2s orbitals are treated as correlation active orbitals.a
| Active space | Reference inactive correlation inactive | Reference inactive correlation active | Reference activecorrelation active | Virtual orbitals |
|---|---|---|---|---|
| CAS(18,12) | 1a1, 1b1, 2a1 | 3a1, 2b1, 4a1, 5a1, 3b1, 1b2, 6a1, 1a2, 4b1, 2b2, 7a1, 5b1 | 8a1, 6b1, etc. | |
| Ref. | 6 | 18 | 0 | |
| Ref. + SD | 6 | 16-18 | 0-2 | |
| Ref. + SDT | 6 | 15-18 | 0-3 | |
| Ref. + SDTQ | 6 | 14-18 | 0-4 | |
| CAS(18,10) | 1a1, 1b1, 2a1 | 3a1, 2b1, 4a1, 5a1, 3b1, 1b2, 6a1, 1a2, 4b1, 2b2 | 7a1, 5b1,8a1, 6b1, etc. | |
| Ref. | 6 | 18 | 0 | |
| Ref. + SD | 6 | 16-18 | 0-2 | |
| Ref. + SDT | 6 | 15-18 | 0-3 | |
| Ref. + SDTQ | 6 | 14-18 | 0-4 | |
| CAS(6,4) | 1a1, 1b1, 2a1 | 3a1, 2b1, 4a1, 5a1, 3b1, 1b2 | 6a1, 1a2, 4b1, 2b2 | 7a1, 5b1, 8a1, 6b1, etc. |
| Ref. | 6 | 12 | 6 | 0 |
| Ref. + SD | 6 | 10-12 | 4-8 | 0-2 |
| Ref. + SDT | 6 | 9-12 | 3-8 | 0-3 |
| Ref. + SDTQ | 6 | 8-12 | 2-8 | 0-4 |
| CAS(2,2) | 1a1, 1b1, 2a1 | 3a1, 2b1, 4a1, 5a1, 3b1, 1b2, 6a1, 1a2 | 4b1, 2b2 | 7a1, 5b1, 8a1, 6b1, etc. |
| Ref. | 6 | 16 | 2 | 0 |
| Ref. + SD | 6 | 14-16 | 0-4 | 0-2 |
| Ref. + SDT | 6 | 13-16 | 0-4 | 0-3 |
| Ref. + SDTQ | 6 | 12-16 | 0-4 | 0-4 |
a
See Section IV B for detailed explanations.