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**Questions and Answers / Gibbs free energy calculation**

« **on:**October 7, 2021, 13:27 »

Hello

The total energy of a molecule is negative when calculated using TotalEnergy() function: https://docs.quantumatk.com/manual/Types/TotalEnergy/TotalEnergy.html

When I calculate the free (vibrational) energy of the same molecule it is a positive number using the freeEnergy() function: https://docs.quantumatk.com/manual/Types/PhononDensityOfStates/PhononDensityOfStates.html

I want to calculate the Gibbs free energy therefore should I add the total energy obtained from TotalEnergy() and the vibrational free energy obtained from phonon_density_of_states.freeEnergy()? E.g. if the TotalEnergy() gives -20eV and freeEnergy() gives +1eV, is it true that Gibbs free energy of the molecule is -20+1=-19eV?

Thanks a lot.

The total energy of a molecule is negative when calculated using TotalEnergy() function: https://docs.quantumatk.com/manual/Types/TotalEnergy/TotalEnergy.html

When I calculate the free (vibrational) energy of the same molecule it is a positive number using the freeEnergy() function: https://docs.quantumatk.com/manual/Types/PhononDensityOfStates/PhononDensityOfStates.html

I want to calculate the Gibbs free energy therefore should I add the total energy obtained from TotalEnergy() and the vibrational free energy obtained from phonon_density_of_states.freeEnergy()? E.g. if the TotalEnergy() gives -20eV and freeEnergy() gives +1eV, is it true that Gibbs free energy of the molecule is -20+1=-19eV?

Thanks a lot.