Question

What is the meaning of free energy out of equilibrium?

Answer 1

So in statistical mechanics the free energy FF(either canonical or grand canonical) can be found from the partition sum ZZ as:

Z=exp(−βF).Z=exp⁡(−βF).

As far as I can read it makes no sense to define a partition sum out of equilibrium and hence no sense to talk about a free energy

Answer 2

Free energy, in thermodynamics, energy-like property or state function of a system in thermodynamic equilibrium. ... Free energy is an extensive property, meaningthat its magnitude depends on the amount of a substance in a given thermodynamic state.