What meanings do the value "Total E, Thermal(internal) energy at 298.15 [K]" have?

[Yuta]

Hi, I’m a biggner of Psi4 and try calculating a reaction energy.

My question is “What does the value “Total E, Thermal(internal) energy at 298.15 [K]” means?”

I’ve found that the values “Total E, Thermal (internal) energy at 298.15 [K]” of each molecules could be used to calculate reaction energy.

I also realized that these values are different from the formation enthalpy.

These values can be seen in log. file like below.

*** Absolute enthalpy, not an enthalpy of formation ***

Thermal (internal) energy, E (includes ZPVE and finite-temperature corrections)
Electronic contrib to E beyond E_e 0.000 [kcal/mol] 0.000 [kJ/mol] 0.00000000 [Eh]
Translational contrib to E 0.889 [kcal/mol] 3.718 [kJ/mol] 0.00141628 [Eh]
Rotational contrib to E 0.889 [kcal/mol] 3.718 [kJ/mol] 0.00141628 [Eh]
Vibrational contrib to E 49.728 [kcal/mol] 208.063 [kJ/mol] 0.07924698 [Eh]
Correction E 51.506 [kcal/mol] 215.500 [kJ/mol] 0.08207954 [Eh]
Total E, Thermal (internal) energy at 298.15 [K] -79.15285550 [Eh]

Thanks for your help.
Best

[crawdad]

The thermal energy at 298.15 K means that the molecular vibrations, rotations, and translations have been accounted for, not just the electronic and nuclear-repulsion energies. You can read about this here: Thermochemistry in Gaussian | Gaussian.com. (This links to the Gaussian website, but all quantum chemistry codes handle it the same way.)

[Yuta]

Dear crawdad,

Thanks for sharing the document! I found the information that I want to know!

Best,