I am trying to find the enthalpies of formation for a couple organometallics in ORCA and as a first time user I am a bit bogged down in the terminology. The Gaussian manual has a section on these calculations (4.3 on page 14) and I am trying to confirm whether the "total energy of the molecules/atoms" is the same as the "inner energy" or "total thermal energy" you can get from the ORCA FREQ calculations.

  • $\begingroup$ The ORCA manual is fairly explicit on most things. One thing to check (with a small molecule, Hartree-Fock, small well-defined basis set) is to set the temperature. Those numbers that change have a thermal component. You should be able to get them to match betwenn the two programs. $\endgroup$
    – TAR86
    Oct 2, 2023 at 11:14
  • $\begingroup$ @Spencer. The title or your questions is a bit misleading. Your are asking about the meaning of the output of a computer program not about a general definition. Could you correct it? $\endgroup$
    – PAEP
    Oct 2, 2023 at 21:23


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