In a Frequencies calculation the computed harmonic frequencies are printed. If a complete variation of coordinates has taken place, the program will compute the frequencies and normal modes also in terms of Symmetry Coordinates, along with the representation in the coordinates that were specified in input.
The zero-point energy is printed, computed as sum over frequencies:
E0 = ∑ ν/2 (4.2.1)
Any imaginary frequencies (printed in the output file as negative frequencies) are not included in the summation.
Thermodynamic properties (Heat Capacity, Entropy, Internal Energy) are printed, based on the ideal gas approximation. Electronic contributions are omitted. These are small when the energy gap with the next electronic configuration is large compared with the vibrational frequencies. For (near) degenerate configurations this assumption is incorrect.
Imaginary frequencies and very small frequencies are ignored in this calculation.
