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.