Miscibility and Transport Properties in Hydrogen-Neon Mixtures

The mixing behavior of hydrogen with heavier elements plays a key role in modeling the interiors of giant planets such as Jupiter and Saturn. Using density functional theory combined with molecular dynamics, we investigate hydrogen-neon mixtures and find that the minimum pressure required to trigger phase separation is substantially lower than in hydrogen-helium mixtures. Our simulations further reveal that the presence of neon stabilizes hydrogen molecules even at temperatures of 10000 K and pressures of 10 Mbar, similar to trends observed in hydrogen-helium mixtures but significantly more pronounced. This stabilization is accompanied by a reduction of several orders of magnitude in the electrical conductivity compared to pure hydrogen. These results, together with the larger X-ray scattering cross section of neon, establish hydrogen-neon as a valuable experimental surrogate for probing phase separation in hydrogen-rich mixtures and provide new insight into the physical mechanisms in hydrogen and mixtures with heavier elements under planetary interior conditions