The next input file gives an example of the input needed for evaluating the two parameters determining an NMR spectrum, the nuclear shielding constants and the spin-spin coupling constants. We do this at a fixed geometry, and use a Restricted Active Space (RAS) wave function. In this way we include near-degeneracy effects by inclusion of the appropriate orbitals in the RAS2 space, and also some of the dynamical correlation by single and double excitations from the RAS2 space (and generally also form the RAS1 space) into the RAS3 space.
In this input we once more use water as input molecule, where we keep the 1s orbital inactive, correlate 8 electrons in 6 orbitals (Full-Valence CAS) and in addition allow single- and double-excitations into 7 additional orbitals.
| **DALTON INPUT | |
| .RUN PROPERTIES | Run integrals, wave function and properties |
| ***WAVE FUNCTIONS | |
| .HF | |
| .MP2 | |
| .MCSCF | |
| **SCF INPUT | |
| .DOUBLY OCCUPIED | |
| 3 1 1 0 | |
| **CONFIGURATION INPUT | |
| .SYMMETRY | |
| 1 | |
| .SPIN MUL | |
| 1 | |
| .INACTIVE | |
| 1 0 0 0 | |
| .RAS1 SPACE | # orbitals in RAS1 space |
| 0 0 0 0 | |
| .RAS2 SPACE | The ``Cas Space'' |
| 3 2 1 0 | |
| .RAS3 SPACE | |
| 3 1 2 1 | |
| .ELECTRONS | Number of electrons to correlate |
| 8 | The valence electrons |
| .RAS1 HOLES | # elect. that may be removed from RAS1 |
| 0 0 | |
| .RAS3 ELECTRONS | From 0 to 2 electrons excited into here |
| 0 2 | |
| ***PROPERTIES | Input for single geometry run |
| .SHIELD | |
| .SPIN-S | |
| ***END OF DALTON INPUT |