Building confidence in state-of-the-art ab initio calculations of the density virial coefficients of B and C of helium-4: Part 1. Indirect evaluation methods using the results of SPRIGT

Abstract

In this work, we propose indirect evaluation methods to check the accuracy and the uncertainty of ab initio calculated virial coefficients. To this end, we have used single-pressure refractive-index gas thermometry (SPRIGT) to estimate the impact of the second density virial coefficient B of helium-4 on temperature measurements between 5 K to 25 K. Our results, in good agreement with values of B obtained from recent ab initio calculations by Czachorowski et al. [Phys. Rev. A 102, 042810 (2020)], suggest uncertainties u(B) estimated previously by other authors were too conservative. Concerning the value of the third density virial coefficient C of helium-4, calculated ab initio by Garberoglio et al. [J. Chem. Phys. 134, 134106 (2011)], our results suggest their uncertainty u(C) is between 1.5 and 10.2 times too high.