Vibrationally averaged spin-spin coupling constants

For the calculation of vibrational corrections in indirect spin-spin coupling constants, DALTON provides an alternative approach to the calculation of vibrational corrections, in which also the full point-group symmetry of the molecule is exploited in order to reduce the number of displaced geometries that need to be included. An example of such an input is :

**DALTON INPUT
.NMDDRV
**NMDDRV
.SYMMETRY
  C2v
.VIBANA
.DISPLA
 0.01
*PROPAV
.ANHA-P
**WAVE FUNCTIONS
.HF
*SCF INPUT
.THRESH
 1.0D-12
**PROPERTIES
.SPIN-SPIN
*SPIN-S
.SELECT
  3
  1  2  3
*TRPRSP
.THRESH
1.0D-12
*LINRES
.THRESH
1.0D-12
*END OF INPUT

We note that the input includes the full point group symmetry of the molecule (in this case the water molecule, and thus here given as $C_{2v}$). In this case, the vibrational corrections are evaluated at the equilibrium geometry of the molecule, and both the harmonic and anharmonic contributions are included. The approach is very similar to that presented in the previous two sections, and a detailed description of the two approaches and a comparison of the two methods are given in Ref. []. For information about the special input modules used in the above input example, we refer to Sec. 21.2.