# Doubts about the operation of free energy technology-free sampling

• Hot
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1 year 3 weeks ago #8196 by Hot
Hi, I operated with free sampling of the free energy technique ( Martini tutorials: Free energy techniques ). I've got all the curves between 0 and 1.
I don't understand how to calculate the log(Phexadecane-water), which data should be used.

1 year 2 weeks ago #8204 by riccardo
You are almost there. You need to check the value of the density (horizontal axis) for the acetone bead in the bulk of hexadecane and in the bulk of the water phase. Due to the normalization (which I guess is what you mean by "all the curves between 0 and 1"), the two density values will be both between 0 and 1. Then you take the logarithm of the ratio of the two densities as follows and multiply it by -RT:

ΔG = -RT ln(P) = - gas_constant * temperature * ln (density_ACE_HD / density_ACE_W)

density_ACE_HD = density of acetone in the bulk of the hexadecane phase; density_ACE_W = density of acetone in the bulk of the water phase.
Hope this helps.