Browsing by Subject "DIFFUSION"

Now showing 1 - 4 of 4
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    A microscopic model of the Stokes-Einstein relation in arbitrary dimension.
    (The Journal of chemical physics, 2018-06) Charbonneau, Benoit; Charbonneau, Patrick; Szamel, Grzegorz
    The Stokes-Einstein relation (SER) is one of the most robust and widely employed results from the theory of liquids. Yet sizable deviations can be observed for self-solvation, which cannot be explained by the standard hydrodynamic derivation. Here, we revisit the work of Masters and Madden [J. Chem. Phys. 74, 2450-2459 (1981)], who first solved a statistical mechanics model of the SER using the projection operator formalism. By generalizing their analysis to all spatial dimensions and to partially structured solvents, we identify a potential microscopic origin of some of these deviations. We also reproduce the SER-like result from the exact dynamics of infinite-dimensional fluids.
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    Homogenization of thermal-hydro-mass transfer processes
    (Discrete and Continuous Dynamical Systems - Series S, 2015-02-01) Xu, S; Yue, X
    In the repository, multi-physics processes are induced due to the long-time heat-emitting from the nuclear waste, which is modeled as a nonlinear system with oscillating coefficients. In this paper we first derive the homogenized system for the thermal-hydro-mass transfer processes by the technique of two-scale convergence, then present some error estimates for the first order expansions.
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    Selective breakdown of phonon quasiparticles across superionic transition in CuCrSe 2
    (Nature Physics, 2019-01-01) Niedziela, Jennifer; Bansal, Dipanshu; May, Andrew; Ding, Jingxuan; Lanigan-Atkins, Tyson; Ehlers, Georg; Abernathy, Douglas; Said, Ayman; Delaire, Olivier
    © 2018, The Author(s), under exclusive licence to Springer Nature Limited. Superionic crystals exhibit ionic mobilities comparable to liquids while maintaining a periodic crystalline lattice. The atomic dynamics leading to large ionic mobility have long been debated. A central question is whether phonon quasiparticles—which conduct heat in regular solids—survive in the superionic state, where a large fraction of the system exhibits liquid-like behaviour. Here we present the results of energy- and momentum-resolved scattering studies combined with first-principles calculations and show that in the superionic phase of CuCrSe 2 , long-wavelength acoustic phonons capable of heat conduction remain largely intact, whereas specific phonon quasiparticles dominated by the Cu ions break down as a result of anharmonicity and disorder. The weak bonding and large anharmonicity of the Cu sublattice are present already in the normal ordered state, resulting in low thermal conductivity even below the superionic transition. These results demonstrate that anharmonic phonon dynamics are at the origin of low thermal conductivity and superionicity in this class of materials.
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    Understanding the Social Learning Effect in Contagious Switching Behavior
    (Management Science, 2019-10) Hu, MM; Yang, S; Xu, DY