The second virial coefficient of quadrupolar two center Lennard-Jones models

Abstract

The second virial coefficient of 2-center Lennard-Jones molecules which have an embedded point quadrupole has been determined ia numerical integration. A number of models with different reduced bond lengths and quadrupole moments have been considered. For each model the second virial coefficient has been determined for a range of temperatures. It is shown that the presence of the quadrupole moment significantly raises the Boyle temperature and, for a certain temperature, reduces the value of the second virial coefficient with respect to the non-polar model. Empirical fits for B2 are given which reproduce the generated data. It is also shown that the inclusion of the quadrupole considerably improves the description of B2 for real substances which have a significant quadrupole moment, as is the case for CO2 . The inclusion of the quadrupole is also required for understanding the cross virial coefficient between a spherical and a quadrupolar molecule, for example the interaction between Xe and CO2.