Avoiding Interpolation Errors for Computed Second Virial Coefficients of Noble Gases

Virial coefficients for noble gases calculated from first principles play a key role in gas-based temperature and pressure metrology. They have typically been presented in tabular form, but as smaller uncertainties are achieved the uncertainty introduced by interpolation between tabulated points can become significant. We demonstrate these interpolation errors for the second density and acoustic virial coefficients of 4He and for the second density virial coefficients of Ne and Ar. We then offer an alternative approach, using simple scripts along with a data structure containing precalculated phase shifts to generate these coefficients at any temperature of metrological interest. The approach is applied to the state-of-the-art pair potentials for 3He, 4He, Ne, and Ar, and the software and data tables are made available for general use.