6.18.3 Procedures for frequency calculations

In all cases the geometry is optimized for all degrees of freedom before computing the frequencies. Variables on which the Z-matrix depends are not modified. The hessian is computed by finite differences from analytical energy gradients. Frequencies, intensities, and thermodynamic quantities are evaluated and printed in the output. The summary at the end shows only the energies.

freqscf

Performs SCF frequency calculation.

freqdft

Performs DFT frequency calculation.

freqmp2

Performs MP2 frequency calculation.

freqcas

Performs CASSCF frequency calculation. The procedure does not support state-averaged calculations.

Note: in most cases the SCF calculation is not performed if starting orbitals are found. Several procedures may be specified after each other.