Classical trajectory calculations of diffusion and viscosity for He-N2mixtures

Abstract

The authors present classical trajectory (CT) calculations for the diffusion and viscosity coefficients in the temperature range 77.3-1100K using the HFD1 surface of Fuchs et al. (1984). They have also performed energy-sudden (ES) calculations for this surface and classical infinite-order sudden (MM) calculations for both this surface and their HFD2 surface. The authors CT results agree with the measurements of Kestin et al. (1979) for the viscosity coefficient over the entire range of temperatures reported (298-973K), and for the diffusion coefficient in the temperature range 298-763K. Their error limits are +or-1% for viscosity and +or-2% for diffusion. However the authors' values consistently exceed by about 2% the measurements of Trengove and Dunlop (1982) for diffusion in the temperature range 277-323K, where their error estimate is +or-0.2%. Comparison of the ES results with the CT and the MM results indicates that the ES and MM (IOS) approximations are reasonable for viscosity but less reliable for diffusion. The MM results for both diffusion and viscosity are generally consistent with the quantal infinite-order sudden results for both surfaces, which suggests that quantal effects for these coefficients are relatively small. From the MM results it may be inferred that the HFD1 surface is better than the HFD2 surface for these properties.