Temperature- and composition-dependent hydrogen diffusivity in palladium from statistically-averaged molecular dynamics

doi:10.1016/j.scriptamat.2018.02.010

Title: Temperature- and composition-dependent hydrogen diffusivity in palladium from statistically-averaged molecular dynamics

Abstract

Solid-state hydrogen storage materials undergo complex phase transformations whose kinetics is often limited by hydrogen diffusion. Among metal hydrides, palladium hydride undergoes a diffusional phase transformation upon hydrogen uptake, during which the hydrogen diffusivity varies with hydrogen composition and temperature. Here we perform robust statistically-averaged molecular dynamics simulations to obtain a well-converged analytical expression for hydrogen diffusivity in bulk palladium that is valid throughout all stages of the reaction. Our studies confirm significant dependence of the diffusivity on composition and temperature that elucidate key trends in the available experimental measurements. Whereas at low hydrogen compositions, a single process dominates, at high hydrogen compositions, diffusion is found to exhibit behavior consistent with multiple hopping barriers. Further analysis, supported by nudged elastic band computations, suggests that the multi-barrier diffusion can be interpreted as two distinct mechanisms corresponding to hydrogen-rich and hydrogen-poor local environments.

Authors:

Zhou, Xiaowang ^[1]; Heo, Tae Wook ^[2]; Wood, Brandon C. ^[2]; Stavila, Vitalie ^[1]; Kang, Shinyoung ^[2]; Allendorf, Mark D. ^[1]

Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Publication Date:: 2018-03-09

Research Org.:: Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Sponsoring Org.:: USDOE National Nuclear Security Administration (NNSA); USDOE Office of Energy Efficiency and Renewable Energy (EERE)

OSTI Identifier:: 1429694

Alternate Identifier(s):: OSTI ID: 1489477; OSTI ID: 1548604

Report Number(s):: SAND-2017-12692J; LLNL-JRNL-755044
Journal ID: ISSN 1359-6462; 658955

Grant/Contract Number:: AC04-94AL85000; AC52-07NA27344; NA-0003525

Resource Type:: Accepted Manuscript

Journal Name:: Scripta Materialia

Additional Journal Information:: Journal Volume: 149; Journal ID: ISSN 1359-6462

Publisher:: Elsevier

Country of Publication:: United States

Language:: English

Subject:: 36 MATERIALS SCIENCE

Citation Formats


                    Zhou, Xiaowang, Heo, Tae Wook, Wood, Brandon C., Stavila, Vitalie, Kang, Shinyoung, and Allendorf, Mark D. Temperature- and composition-dependent hydrogen diffusivity in palladium from statistically-averaged molecular dynamics.  United States: N. p., 2018. 
        Web.  doi:10.1016/j.scriptamat.2018.02.010.

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                    Zhou, Xiaowang, Heo, Tae Wook, Wood, Brandon C., Stavila, Vitalie, Kang, Shinyoung, & Allendorf, Mark D. Temperature- and composition-dependent hydrogen diffusivity in palladium from statistically-averaged molecular dynamics.  United States.  doi:10.1016/j.scriptamat.2018.02.010.

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                    Zhou, Xiaowang, Heo, Tae Wook, Wood, Brandon C., Stavila, Vitalie, Kang, Shinyoung, and Allendorf, Mark D. Fri .  
        "Temperature- and composition-dependent hydrogen diffusivity in palladium from statistically-averaged molecular dynamics".  United States.  doi:10.1016/j.scriptamat.2018.02.010.  https://www.osti.gov/servlets/purl/1429694.

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@article{osti_1429694,

  title        = {Temperature- and composition-dependent hydrogen diffusivity in palladium from statistically-averaged molecular dynamics},

  author       = {Zhou, Xiaowang and Heo, Tae Wook and Wood, Brandon C. and Stavila, Vitalie and Kang, Shinyoung and Allendorf, Mark D.},

  abstractNote = {Solid-state hydrogen storage materials undergo complex phase transformations whose kinetics is often limited by hydrogen diffusion. Among metal hydrides, palladium hydride undergoes a diffusional phase transformation upon hydrogen uptake, during which the hydrogen diffusivity varies with hydrogen composition and temperature. Here we perform robust statistically-averaged molecular dynamics simulations to obtain a well-converged analytical expression for hydrogen diffusivity in bulk palladium that is valid throughout all stages of the reaction. Our studies confirm significant dependence of the diffusivity on composition and temperature that elucidate key trends in the available experimental measurements. Whereas at low hydrogen compositions, a single process dominates, at high hydrogen compositions, diffusion is found to exhibit behavior consistent with multiple hopping barriers. Further analysis, supported by nudged elastic band computations, suggests that the multi-barrier diffusion can be interpreted as two distinct mechanisms corresponding to hydrogen-rich and hydrogen-poor local environments.},

  doi          = {10.1016/j.scriptamat.2018.02.010},

  journal      = {Scripta Materialia},

  number       = ,

  volume       = 149,

  place        = {United States},

  year         = {2018},

  month        = {3}

}

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DOI: 10.1016/j.scriptamat.2018.02.010

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Figures / Tables:

Figure 1: Arrhenius plots at different hydrogen compositions of (a) x = 0.4; (b) x = 0.7; (c) x = 0.8; and (d) x = 0.9. Lines are fitted to Eqs. (1) - (5).

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