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A modified potential based on the individually damped model of Douketis, Scoles, Marchetti, Zen, and Thakkar [J. Chem. Phys. 76, 3057 (1982)] is presented which fits, within experimental error, the accurate ultraviolet (UV) vibration-rotation spectrum of argon determined by UV laser absorption spectroscopy by Herman, LaRocque, and Stoicheff [J. Chem. Phys. 89, 4535 (1988)]. Other literature potentials fail to do so. The potential also is shown to predict a large number of other properties and is probably the most accurate characterization of the argon interaction constructed to date. [ABSTRACT FROM AUTHOR]

Obtaining a ground state potential energy curve for helium has been the subject of much research involving empirical, semiempirical, and ab initio methods. In this work, we examine critically recent ab initio potentials proposed for this interaction with respect to their ability to predict certain accurate experimental data. To accomplish this analysis, potentials with a modified HFD-B form were fit to the recent theoretical work of van Duijneveldt and co-workers [Vos, van Lenthe, and van Duijneveldt, J. Chem. Phys. 93, 643 (1990) and Vos, van Mourik, van Lenthe, and van Duijneveldt (to be published)] and Liu and McLean (LM-2) [J. Chem. Phys. 91, 2348 (1989)]. A well depth (ε/k=10.92 K) and a separation at the minimum (rm=2.9702 A) consistent with both determinations were chosen and the properties of helium were calculated based on these potentials. These ‘‘mimic’’ potentials fail to predict the very low temperature 4He and 3He virials and one of them [Vos, van Maurik, van Lenthe, and van Duijneveldt (to be published)] also fails to predict the very accurate room temperature viscosity of Vogel [Ber. Bunsenges. Phys. Chem. 88, 997 (1984)]. For a potential which was fit as closely as possible to the LM-2 potential at its maximum suggested depth (ε/k=10.97 K), the virials are satisfactorily predicted. This compromise potential appears to be the best characterization of the He–He interaction in its ability to predict a variety of experimental data as well as being consistent with ab initio results. [ABSTRACT FROM AUTHOR]

Second virial coefficient data and viscosity were used to evaluate effective isotropic intermolecular potential functions proposed in the literature for sulfur hexafluoride. It was found that none of the potentials could predict the properties simultaneously. We have constructed a Morse–Morse–Spline–van der Waals (MMSV) potential which satisfactorily correlates second virial coefficient and viscosity data at the same time. [ABSTRACT FROM AUTHOR]

The repulsive wall of the Ar–Ar interaction is reexamined with the purpose of rationalizing the apparent inconsistency between high energy beam results and high temperature transport data. A new piece-wise experimental potential is proposed which predicts not only the beam results but a large set of transport data up to 7000 K. Lower temperature/energy data are predicted almost equally as well as other state-of-the-art empirical potentials. [ABSTRACT FROM AUTHOR]

The neon–argon interaction has been reexamined in the light of new data, both theoretical and experimental. Two recent potentials have been analyzed as to their ability to predict both macro- and microscopic properties. Both of these fail to give a complete description of the interaction. A new simple potential is presented which accurately predicts a wide range of properties including high and low energy total cross sections, differential cross section, as well as second virials, viscosity, and diffusion. New combining rules have been tested and are found to be consistent with the new potential. [ABSTRACT FROM AUTHOR]

It is shown how to determine the matrix elements needed to calculate the viscosity and thermal conductivity of a pure atomic gas in arbitrarily high approximation to the solution of the Boltzmann equation. For the first time, explicit expressions are given for calculating the fourth and fifth approximations. Computer programs based on these expressions have been tested for various models of the interatomic interaction potential. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]