Isothermalisobaric molecular dynamics simulation of diatomic liquids and their mixtures

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Isothermalisobaric ensemble molecular dynamics simulations have been performed for systems of two-center Lennard-Jones molecules for pure fluids as well as binary mixtures. The results obtained from various ensemble averages have been compared for pure fluid simulations of Lennard-Jones model diatomic fluids. The excess enthalpy and excess volume of three equimolar mixtures (argonnitrogen, argonoxygen, and nitrogenoxygen) have been calculated and compared with values obtained from previous NVT molecular dynamics and perturbation theory. Pair distribution functions obtained from various methods are compared for the equimolar mixture of nitrogen and oxygen and used to study the effect of attractive forces on the local structure. For four other systems (argonethane, methaneethane, carbon disulfidecarbon tetrachloride, and carbon disulfidetetrachloroethylene), excess enthalpies and excess volumes from NPT simulations are used to test the ability of perturbation theory to predict these properties and are also compared with experimental data. The comparison of simulation and experiment clearly shows the need to improve the available parameters for cross interactions in binary mixtures.