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As I asked this once before and did not get an answer, I will reiterate my question. Is the VASP free energy calculated by U+PV-TS, including the PV term that might occur when relaxing with nonzero strain?

If the PV term is not included in the VASP free energy, then one cannot do strain calculations directly by comparing the free energies of different phases at each strain.

Some people are doing strain calculations assuming the PV term is included, while others have calculated it separately; it is very odd that this is not explained anywhere in the VASP manual.

G=H-TS=H=U+PV at temperature T=0 vasp calculates Free energy F=U-TS, maybe derived from mermin paper, minimize the grand potential

[quote="H-TS=H=U+PV at temperature T=0 vasp calculates Free energy F=U-TS, maybe derived from mermin paper, minimize the grand potential[/quote"]

I would like someone to clarify this to me, perhaps in complete English sentences. Does this mean that VASP does NOT calculate the Gibbs free energy, and thus it cannot be used for strain calculations?

What I want to do is compare the Gibbs free energies of different phases at given nonzero strain (and, therefore, nonzero pressure), to find the phase with the lowest total Gibbs free energy.

The PV term is not included in the total energy written in VASP, the free energy (TOTEN) is U-TS (=H).