Part one, Virial, takes as input a set of values for the second virial coefficient for a non–ideal gas $B(T_i)$ at different temperatures $T_i$, measured or otherwise obtained elsewhere, as well as a set of intermolecular potential parameters (Lennard–Jones parameters and a quadrupole moment). Virial generates a function B(T) from theory which is plotted together with the experimental data. The potential parameters can be adjusted interactively in a graphical window in order to match the theoretical B(T) curve with the experimental data. The Virial module can therefore be used to obtain a set of intermolecular potential parameters for subsequent molecular dynamics or Monte Carlo simulations of a nonideal system, with the potential parameters being chosen such that they yield the correct B(T).