How to calculate the residual part of the Gibbs free energy?
 

Hi,
I want to obtain the critical radius of non-equilibirum condensation with my own expression in the CFD-Post.
R_cri=2*Tension/Density_liq/dG
dG is the residual part of the Gibbs free energy bettween actual state and saturated state at a constant vapor temperature.
dG=G(p,T_vap)-G_sat(p_sat,Tvap)

How to calculated the dG ?