What type of energy Avogadro calculate?

In molecular Mechanics option Avogadro have an option to calculate the energy

What type of energy are that?
Gibs free energy?
Activation energy?
Enthalpy? If it’s enthalpy what type? Fusion, Sublimation or vaporization?

It’s not really any of those.

  • Gibbs Free Energy requires calculating entropy
  • Activation Energy is for a reaction - it would be hard to know what reaction you want … and even so it typically requires finding the transition state
  • Entropy - no, because there are many contributions from entropy, including translational, rotational, vibrational and conformational - not all of which can be directly computed from one geometry
  • Enthalpy - many of the force fields attempt to calculate a heat of formation. I mention “attempt” because they’re not tremendously accurate. They’re intended to give a fast rough approximation to quantum mechanical effects

(Enthalpy of fusion, sublimation or vaporization would all require calculating many, many molecules at once.)

tldr - it’s some very rough approximation of a heat of formation but I wouldn’t consider it too accurate