Classical trajectory calculations of transport properties for a model Ar-N2potential surface

Abstract

Classical trajectory calculations were performed using the Ar-N2 potential surface of Patterngill et al. (1979) for temperatures of 77.3 and 300K. Diffusion and viscosity cross sections, the production and relaxation cross sections governing the viscomagnetic effect and cross sections for both depolarised Rayleigh scattering and the rotational relaxation time were calculated. Comparison was made with classical energy-sudden (ES), classical infinite-order sudden (MM) and quantal infinite-order sudden (IOS) calculations. For both the viscosity and diffusion cross sections the CT and the ES, MM and IOS calculations agree within 3%, except for the IOS results at 77.3K. For the relaxation and DPR cross sections the IOS results are found to differ by about 40-80% from the CT results. The ES result for the DPR cross section is about 20% larger than the CT result, while for the production and relaxation cross sections it is very poor. The authors suggest that the main reason for these discrepancies is the breakdown of the sudden approximation for the non-sudden collisions always arising in thermal averages.