The effect of intermolecular interactions on the electric properties of helium and argon. Part III: Quantum statistical calculations of the dielectric second virial coefficients

Antonio Rizzo
Istituto di Chimica Quantistica ed Energetica Moleculare del Consiglio Nazionale delle Ricerche, I-56126 Pisa, Italy

Christof Hättig
Forschungszentrum Karlsruhe, Institute of Nanotechnology, P.O. Box 3640,D-76021 Karlsruhe, Germany

Berta Fernández
Department of Physical Chemistry, Faculty of Chemistry, University of Santiago de Compostela, E-15706 Santiago de Compostela, Spain

Henrik Koch
Department of Chemistry, University of Odense, DK-5230 Odense M, Denmark

J. Chem. Phys. 117, 2609-2618 (2002).

The second dielectric virial coefficients of helium and argon are investigated using a fully quantum statistical approach and recent accurate ab initio results for the interatomic potentials and the interaction-induced polarizabilities. We thereby extent a previous investigation of the virial coefficients which was based on a semiclassical approach to include quantum effects. For helium our results support the finding of a previous quantum statistical study that quantum effects are substantial for temperatures below 10 K, while they are practically negligible above 70 K. For argon quasi-bound states in the continuum and a slow convergence of the summation over the angular momentum require special treatments in the numerical integrations that have to be carried out in the quantum statistical calculation of the virial coefficients. The results show that for argon quantum effects are practically negligible in the investigated range of temperatures 242.95 -- 406.6 K. The comparison with the experimental data is for helium reasonable above 70 K, but for lower temperatures large descrepancies are found with some of the experimental measurements. Since for argon the quantum effects are only small they do not change the comparison of our previous study between the experimental data and the ab initio calculated values. While some of the experimental results are in good agreement with the ab initio calculations, a number of experiments are in disagreement with the theoretical results.

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