Recommended Second Virial Coefficients for Nitrogen and Oxygen

Abstract

We provide recommended values for the second virial coefficient, B(T), and its uncertainty, for molecular nitrogen and oxygen. The temperature range covered is 20–3000 K for nitrogen and 20–2000 K for oxygen. The recommendations are based on tuning previously published state-of-the-art ab initio pair potentials so that the B(T) calculated from the potentials match selected high-accuracy experimental data; for nitrogen the tuning utilizes values of B derived from literature density data with greatly reduced uncertainty by analyzing the data with the aid of ab initio calculated higher virial coefficients. Quantum effects on B are fully included with the path-integral Monte Carlo method. The resulting B(T) have uncertainties similar to those of the best experimental data, but cover a much wider temperature range.