Shear viscosity coefficient of dilute gases via the ANC2s interaction potential

Molecular dynamics simulations and kinetic theory at the level of the Chapman-Enskog approximation were used to study repulsive and attractive contributions for a family of non-conformal potentials. The analysis was performed for the shear viscosity coefficient in the dilute-gas limit. To obtain a set of parameters to adequately model molecular interactions, collision integrals from kinetic theory were interpolated using experimental data on spherical and quasi-spherical molecular systems. Theoretical and simulation results show relative differences of 0.6%-2.3% and 0.4%-3.7% when comparing experimental data, respectively. The accuracy of the Chapman-Enskog first-order approximation was estimated using a Chapman-Cowling third-order correction. Results estimated to first order display differences of up to 0.8% when compared to higher-order corrections. Molecular interactions were modeled using the potential from the Approximate Non-Conformal (ANC) theory, which depends on length and energy scales, in addition to a softness parameter. A more refined version of the theory denoted ANC2s modulates repulsive and attractive contributions independently, for which the "2s" is mnemonic for the corresponding two softness parameters. In this work, we illustrate the robustness of the ANC2s representation by capturing the shear viscosity coefficient in the dilute-gas limit for a variety of molecular systems and by reproducing other interaction potentials, in particular, the Lennard-Jones 9-6, 12-6, and 20-6 forms.