.. include:: autodoc_abbr_options_c.rst .. index:: single: harmonic vibrational analysis, vibrational analysis, thermochemical analysis .. _`sec:thermo`: Vibrational and Thermochemical Analysis ======================================= .. codeauthor:: Rollin A. King .. comment.. sectionauthor:: Rollin A. King and Lori A. Burns *Module:* :ref:`Keywords `, :ref:`PSI Variables `, :source:`THERMO ` .. caution:: It is important to know that |PSIfour|, like any other quantum chemistry program, does *not* compute the usual enthalpies, entropies, or Gibbs free energies *of formation* provided by most reference books. Instead, quantum chemistry programs compute "absolute" thermodynamic properties relative to infinitely separated nuclei and electrons, not "formation" values relative to elements in their standard states. If you are computing thermodynamic differences, like a reaction enthalpy computed as the enthalpy of the products minus the enthalpy of the reactants, then these "absolute" enthalpies are perfectly valid and usable. However, they cannot be mixed and matched with enthalpies of formation from reference books, since the zero of energy is not the same. Additionally, the "thermal energies" reported in kcal/mol are the finite-temperature *corrections* to the electronic total energy, and not the overall thermal energies themselves. If in doubt, use the reported Total Energies in Hartree/particle. Keywords ^^^^^^^^ .. include:: autodir_options_c/thermo__t.rst .. include:: autodir_options_c/thermo__p.rst .. include:: autodir_options_c/thermo__rotational_symmetry_number.rst .. _`sec:thermoExamples`: Examples ^^^^^^^^ .. index:: pair: vibrational analysis; output Output ^^^^^^ Text, text everywhere, and not a character on point. :: --------------------------------------------------------------------------------------------- ~ Step Total Energy Delta E MAX Force RMS Force MAX Disp RMS Disp ~ --------------------------------------------------------------------------------------------- ~ Convergence Criteria 1.00e-06 * 3.00e-04 * o 1.20e-03 * o ~ --------------------------------------------------------------------------------------------- ~ 1 -38.91591820 -3.89e+01 6.91e-02 5.72e-02 o 1.42e-01 1.19e-01 o ~ 2 -38.92529543 -9.38e-03 6.21e-03 3.91e-03 o 2.00e-02 1.18e-02 o ~ 3 -38.92540669 -1.11e-04 4.04e-03 2.46e-03 o 3.63e-02 2.12e-02 o ~ 4 -38.92548668 -8.00e-05 2.30e-04 * 1.92e-04 o 1.99e-03 1.17e-03 o ~ 5 -38.92548698 -2.98e-07 * 3.95e-05 * 3.35e-05 o 1.37e-04 * 1.05e-04 o ~ The full list of keywords for thermo is provided in Appendix :ref:`apdx:thermo`. Information on the Psithon function that drives frequency analyses is provided at :py:func:`~driver.frequency`.