title: Transport properties of hydrogen-helium mixtures at extreme density and temperature conditions.
abstract: We perform a systematic study of hydrogen-helium mixtures using quantum molecular dynamics (QMD) with a focus on the equations of state and structural and transport properties such as electrical conductivity, diffusion, and viscosity at conditions of giant planet interiors of 0.2∼2.3 g/cm(3) and 1000∼80,000 K for a typical helium mass fraction of 0.245. The H-He separation is found at low temperatures by analyzing the trajectories and pair distribution functions. We show that the diffusion coefficients exhibit transitions from kinetics- to potential-, and then to demixing-dominated regimes. In addition, we identify the discontinuity feature of optical absorption of a H-He mixture at low density and temperature conditions, which results from the change from an intraband to an interband transition. The Stokes-Einstein relation between the diffusion and viscosity coefficients is also discussed.
authors.affiliation: Institute of Applied Physics and Computational Mathematics, P.O. Box 8009, Beijing 100088, People's Republic of China.
authors.forename: Dafang
authors.initials: D
authors.lastname: Li
authors.affiliation: Institute of Applied Physics and Computational Mathematics, P.O. Box 8009, Beijing 100088, People's Republic of China.|Center for Applied Physics and Technology, Peking University, Beijing 100871, People's Republic of China.
authors.forename: Cong
authors.initials: C
authors.lastname: Wang
authors.affiliation: Center for Applied Physics and Technology, Peking University, Beijing 100871, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Kang
authors.affiliation: Institute of Applied Physics and Computational Mathematics, P.O. Box 8009, Beijing 100088, People's Republic of China.|Center for Applied Physics and Technology, Peking University, Beijing 100871, People's Republic of China.
authors.forename: Jun
authors.initials: J
authors.lastname: Yan
authors.affiliation: Institute of Applied Physics and Computational Mathematics, P.O. Box 8009, Beijing 100088, People's Republic of China.|Center for Applied Physics and Technology, Peking University, Beijing 100871, People's Republic of China.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhang