# Parameter determining argon phase

Currently I am working a molecular simulation to determine phases of an argon NPT ensemble using Lennard Jones potential. Mainly I use the radial distribution function to determine solid, liquid, or vapor state by investigating the structure.

A problem comes in when I notice that there are some states which should be in vapor form that exhibit the radial distribution function of liquid (showing a widen peak). I surmise that there may be due to the high density gas especially above the critical point.

Is there any way to decisively differentiate the liquid and vapor phase?

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What's your N? By the way "some states which should be in vapor form" --- why do you think they should be in a vapor form? –  Yrogirg Dec 25 '12 at 4:13