Thermochemistry

Harmonic frequency analysis computes thermodynamic properties at a given temperature and pressure.

Harmonic Frequency Analysis with Thermochemistry

task: FREQ RHF STO-3G

GEOMETRY
  O   0.000000   0.000000   0.117369
  H   0.756950   0.000000  -0.469476
  H  -0.756950   0.000000  -0.469476
END

FREQ
  Hessian     analytical
  Temperature 298.15
  Pressure    1.0
  Scale       1.0
END

Custom Conditions

FREQ
  Temperature 350.0
  Pressure    1.0
  Scale       0.9854
END

Output

The thermochemistry output includes:

Zero-Point Energy:            0.05895 Hartree
Thermal Correction (E):       0.06123 Hartree
Thermal Correction (H):       0.06217 Hartree
Thermal Correction (G):       0.04188 Hartree
Entropy:                      0.04432 Hartree/K

Symmetry Number

The symmetry number σ is automatically determined from the detected point group:

Point Group	σ
C₁	1
Cₙ	n
Dₙ	2n
T_d	12
O_h	24
C∞ᵥ	1
D∞ₕ	2

Override with SymmetryNumber N in the FREQ section if needed.

Read/Save Hessian

FREQ
  Read  myjob.oqd
END

FREQ
  Save true
END