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AlessioM

Member

Registered: 2022-10-11

Posts: 11

Energy from gaussian output files

Dear Prof Tian Lu,

I have a question about the energy value obtained from the Gaussian output file.

I've done opt + freq calculation on dichloromethane at B3LYP 6-31+G* as an example and I get an E(B3LYP)=-959.700528 HARTREE/PARTICLE, I know that this energy is related to complete dissociation reaction of the molecule. 

If i use a 1 Hartree = 627.5 kcal/mol i get a huge number to be an energy value, is this correct?

Or is there another way to obtain an energy value in kcal/mol more reliable by common sense?

Thanks a lot !

Alessio Macorano

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,830

Website

Re: Energy from gaussian output files

Dear Alessio Macorano,

What you calculated is electronic energy, rather than energy of complete dissociation reaction of the molecule.

The concept in quantum chemistry field closest to the so-called "energy of complete dissociation reaction of a molecule" is atomization energy. For example, for H2O molecule you should calculate 2*E(H) + E(O) - E(H2O).

Best,

Tian