Transport properties of a quasisymmetric binary nitrogen-oxygen mixture in the warm dense regime

Transport properties of mixtures in the warm dense matter (WDM) regime play an important role in natural astrophysics. However, a physical understanding of ionic transport properties in quasisymmetric liquid mixtures has remained elusive. Here, we present extensive ab initio molecular dynamics (AIMD) simulations on the ionic diffusion and viscosity of a quasisymmetric binary nitrogen-oxygen (N-O) mixture in a wide warm dense regime of 8-120 kK and 4.5-8.0 g/cm(3). Diffusion and viscosity of N-O mixtures with different compositions are obtained by using the Green-Kubo formula. Unlike asymmetric mixtures, the change of proportions in N-O mixtures slightly affects the viscosity and diffusion in the strong-coupling region. Furthermore, the AIMD results are used to build and verify a global pseudo-ion in jellium (PIJ) model for ionic transport calculations. The PIJ model succeeds in reproducing the transport properties of N-O mixtures where ionization has occurred, and provides a promising alternative approach to obtaining comparable results to AIMD simulations with relatively small computational costs. Our current results highlight the characteristic features of the quasisymmetric binary mixtures and demonstrate the applicability of the PIJ model in the WDM regime.

Automated summary

Transport properties of mixtures in the warm dense matter (WDM) regime, such as ionic diffusion and viscosity, are crucial in natural astrophysics. In this study, extensive ab initio molecular dynamics (AIMD) simulations were performed on a quasisymmetric binary nitrogen-oxygen (N-O) mixture in a wide range of warm dense conditions (8-120 kK and 4.5-8.0 g/cm(3)). The results showed that the change of proportions in N-O mixtures has only a slight effect on viscosity and diffusion in the strong-coupling region. Additionally, a global pseudo-ion in jellium (PIJ) model was developed and validated for ionic transport calculations, providing a promising alternative approach with relatively low computational costs compared to AIMD simulations.