Estimating the second virial coefficients of some real gas mixtures and related thermodynamic views

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 considered molecules were evaluated and the results wereinterpreted according to the Lennard – Jones equation. In addition, the second virial coefficientof each pair gas was calculated upon the appropriate equations of statistical thermodynamics.The resultant coefficients were almost comparable with those are available in the literature.