NEVPT2 must follow a CAS-SCF or CAS-CI calculation. The keyword .NEVPT2 has to be specified in the **WAVE FUNCTIONS data section. Furthermore a small *NEVPT2 data group can be specified providing the few input data that can optionally be provided by the user: .THRESH, the threshold to discard small coefficients in the CAS wavefunction (default = 0.0), .FROZEN, a vector specifying for each symmetry the core orbitals which are excluded from the correlation treatment (the default is no freezing) and .STATE, the state in a CASCI calculation. This keyword is unnecessary (ignored) in the CASSCF case. An example of a NEVPT2 calculation is
**DALTON INPUT **WAVE FUNCTIONS .MCSCF .NEVPT2 *NEVPT2 .THRESH 1.0D-12 .FROZEN 1 0 1 0 **END OF DALTON INPUT