As experimental measurements of thermodynamic properties have improved in accuracy, to five or six figures, over the decades, cubic equations that are widely used for modern thermodynamic fluid property data banks require ever-increasing numbers of terms with more fitted parameters. Functional forms with continuity for Gibbs density surface ρ(p,T) which accommodate a critical-point singularity ...

Using the Gaussian 2003 software and MP2/ 6–311 ++ G** method for He: He, Ne:Ne andMP2/6-31G method for Ar: Ar, Kr: Kr and HF/STO-3G method for Xe: Xe, the optimizedinteraction energies between two like atoms of rare gases (He, Ne, Ar, Kr and Xe) as a functionof the distances between the centers of two considered atoms were evaluated and the resultswere interpreted according to the Lennard – Jo...

Using the Gaussian 2003 software and MP2 /6 – 311+ G method for the C2H4 : O2, CO:Cl2 andCO2:CO2 pairs and MP2/6-311++G** method for the CO2:H2O pair and B3lyp/6-31G methodfor the O2:O2 pair the optimized interaction energies between two considered pair molecules ofstudied gases(C2H4:O2, CO:Cl2, CO2:H2O, O2:O2 and CO2:CO2 pairs) as a function of thedistances between the centers of two considere...