Exchange-coulomb potential energy curves for He-He, and related physical properties

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Abstract
The investigation of the reliability of the original simple overall damped form of the XC (exchange-Coulomb) potential is extended to the He-He interaction, and a new multidamped version of the XC potential is introduced. New one and two parameter overall damped, and one and two parameter multidamped XC potentials for He-He are constructed. The results obtained from these potentials for the second virial coefficients (1·4 < T < 623 K) and transport properties of dilute He gas, and for integral collision cross-sections for He-He collisions, are compared with experiment and with those obtained with the (reference) HFD-B2 potential. The various XC potentials are explicitly compared, over a wide range of interatomic distances R, with the HFD-B2 potential, with ab initio results and with a very accurate (R ⩽ 3a 0) quantum Monte Carlo potential. While the one parameter versions of the XC potentials generally yield very good results, the two parameter overall and individually damped XC potentials, and the HFD-B2 potential, are of comparable quality and are apparently the most reliable representatives of the He-He interaction available.