The Kr-Kr potential energy curve and related physical properties; the XC and HFD-B potential models

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Abstract
The construction of pair potentials for closed shell systems following the XC (exchange-Coulomb) and the HFD (Hartree-Fock-dispersion) models is reviewed briefly. New XC potentials for Kr-Kr are constructed. It is shown that, unlike previous applications of the original XC potential model, fixing the adjustable parameter(s) in the model by fitting second virial coefficient data alone does not lead to an optimal Kr-Kr potential; this could be due to inconsistencies in the available experimental second virial data for Kr, but more likely is due to a lack of flexibility in the original XC potential model. Two modifications of the original XC potentials are considered and these lead to optimum Kr-Kr interaction energies. Three XC potentials and two HFD-B type potentials are compared with respect to their ability to predict the second virial coefficient and transport properties of dilute Kr gas, the Kr-Kr differential and total scattering cross sections, the spectroscopic properties of the dimer, and the repulsive wall of the potential as determined by high energy beam scattering experiments. One of the HFD-B potentials is a modification of the original HFD-B potential for Kr-Kr, used herein as a standard reference potential, leading to a repulsive wall in agreement with experiment. The recommended potentials of this paper are apparently the most reliable to date for the Kr-Kr pair potential.