R  = 8.314                  # gas constant; J/mol/K
kb = 1.38066E-23            # boltzmann's constant; J/K
c  = 2.997925E8             # speed of light; m/s
N0 = 6.02205E23             # Avagadro's number; /mol
h  = 6.62618E-34            # planck's constant; J*s
hbar = 1.05459E-34          # planck's constant; J/Hz

set data style lines

dH = 20
dS(T) = R/1000 * log(hbar/kb/T*c*100*100)
dG(T) = dH - T*dS(T)