Transport properties of an asymmetric mixture in the dense plasma regime

Abstract

We study how concentration changes ionic transport properties along isobars-isotherms for a mixture of hydrogen and silver, representative of turbulent layers relevant to inertial confinement fusion (ICF) and astrophysics. Hydrogen will typically be fully ionized while silver will be only partially ionized but can have a large effective charge. This will lead to very different physical conditions for the H and Ag. Large first principles orbital free molecular dynamics (OFMD) simulations are performed and the resulting transport properties are analyzed. Comparisons are made with transport theory in the kinetic regime and in the coupled regime. The addition of a small amount of heavy element in a light material has a dramatic effect on viscosity and diffusion of the mixture. This effect is explained through kinetic theory as a manifestation of a crossover between classical diffusion and Lorentz diffusion.

Enhancement of nuclear reaction rates in asymmetric binary ionic mixtures

“…We performed two kinds of simulations. First, to emphasize the effect of temperature, we ran hydrogen–silver simulations at different concentrations and temperatures, from 50 to 2000 eV . Then, to test the effect of the asymmetry of the mixture, we simulated different mixtures with various elements of increasing atomic number: hydrogen–lithium, hydrogen–carbon, hydrogen–aluminium, hydrogen–copper, and hydrogen–silver, with different proportions and at a fixed temperature of 100 eV …”

“…In this section, we consider hydrogen–silver simulations at various temperatures . A key quantity for describing mixtures is the mutual diffusion coefficient, which is given by the correlation of the species currents.…”

“…For a highly asymmetric mixture, such as hydrogen–silver, we have D 2 ≪ D 1 (see Ref. ), so, to a good approximation, the mutual diffusion reduces to the self‐diffusion of the light element times the heavy element concentration D 12 ≃ x 2 D 1 . Hydrogen is fully ionized in the range of temperatures of interest ( Q 1 = 1) and is not correlated.…”

“…In this section, we consider hydrogen-silver simulations at various temperatures. [8] A key quantity for describing mixtures is the mutual diffusion coefficient, which is given by the correlation of the species currents. Simulations show that the mutual diffusion coefficient can be well approximated by the Darken relation where D 1 and D 2 are the self-diffusion coefficients of hydrogen and silver in the mixture.…”

“…First, to emphasize the effect of temperature, we ran hydrogen-silver simulations at different concentrations and temperatures, from 50 to 2000 eV. [8] Then, to test the effect of the asymmetry of the…”