What is Equation of State(EOS) in autotest?

[biglinn]

I have a little problem. When I do dpgen autotest, there is a module named eos(full name is the equation of state). But it is actually a trend curve of energy(per atom) with respect to volume(per atom). It confues me a lot.

I get this figure in the article "DP-GEN: A concurrent learning platform for the generation of reliable
deep learning based potential energy models". But there is no explanation about EOS.
So, I wander whether there are some acticles of EOS theroy.

[biglinn]

It is obvious that the volume corresponding to the minimum energy represents the equilibrium state.
So does it mean that volume larger than this equilibrium volume represents high-temperature condition, and smaller volume to low-temperture?
If the view is right, could I add more data(high or low temperture) depending on where EOS curve is nor well fitted?