Classical trajectory calculation of transport and relaxation properties for CO₂-He mixtures

Two recent CO2-He potential surfaces are tested with respect to their abilities to predict the temperature dependence of the interaction second virial coefficient and the transport properties, including binary diffusion, shear viscosity, thermal conductivity, and thermal diffusion, including their abilities to predict bulk relaxation phenomena, including rotational relaxation, field effects on transport properties, and collision-broadening of the rotational Raman and depolarized Rayleigh lines at room temperature. Fully converged classical trajectory calculations are employed for the determination of these phenomena. Such calculations can be expected to be precise to within ± 0·1% for most of the cross sections that determine the transport coefficients, to ± 1% for the relaxation cross sections, and to within ± 5% for certain of the cross sections that determine the effects of external fields on the transport phenomena. Both potential surfaces fare quite well with respect to the transport properties, with the newer potential faring slightly better than the older one. The newer potential fares considerably better with respect to the temperature dependence of the interaction second virial coefficient and the collision broadening of the rotational Raman lines of the CO2 molecule. The largest differences between the two potential surfaces occur for the cross sections that determine the collision broadening of the depolarized Rayleigh line of CO2 and the transport property field effects. For these quantities differences of as much as 60% between the calculated results for the two surfaces are obtained. Experimental measurements of these phenomena would provide a clean distinction to be made between the two proposed interaction potentials.