Microfield dynamics in dense hydrogen plasmas with high- $Z$ impurities

Journal Article · Mon Jan 09 00:00:00 EST 2017 · Physical Review E

DOI:https://doi.org/10.1103/PhysRevE.95.013204· OSTI ID:1466941

Hau-Riege, Stefan P. ^[1]; Weisheit, Jon ^[2]

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1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2. Rice Univ., Houston, TX (United States). Dept. of Physics & Astronomy

We use large-scale classical molecular dynamics to determine microfield properties for several dense plasma mixtures. By employing quantum statistical potentials (QSPs) to regularize the Coulomb interaction, our simulations follow motions of electrons as well as ions for times long enough to track relaxation phenomena involving both types of particles. Coulomb coupling, relative to temperature, of different pairs of species in the hot, dense matter being simulated ranges from weak to strong. We first study the effect of such coupling differences, along with composition and QSP differences, on the roles of electrons and various mixture components in determining probability distributions of instantaneous, total microfields experienced by the ions. Then, we address two important dynamical questions: (1) How is the quasistatic part of the total field to be extracted from the time-dependent simulation data? (2) Under what conditions does the commonly used approximation of ions with fixed Yukawa-like screening by free electrons accurately describe quasistatic fields? We identify a running, short-time average of the total field at each ion as its slowly evolving, quasistatic part. We consider several ways to specify the averaging interval, and note the influence of ion dynamics in this issue. When all species are weakly coupled, the quasistatic fields have probability distributions agreeing well with those we obtain from simulations of Yukawa-screened ions. However, agreement deteriorates as the coupling between high- Z ions increases well beyond unity, principally because the Yukawa model tends to underestimate the true screening of close high- Z pairs. Lastly, examples of this fact are given, and some consequences for the high-field portions of probability distributions are discussed.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE; USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 1466941
• Alternate ID(s): OSTI ID: 1338647
• Report Number(s): LLNL-JRNL--701388; 834626
• Journal Information: Physical Review E, Journal Name: Physical Review E Journal Issue: 1 Vol. 95; ISSN PLEEE8; ISSN 2470-0045
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY