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@PHDTHESIS{Ting:1047287,
      author       = {Ting, Yin-Ying},
      title        = {{F}irst principles simulations of high-entropy materials
                      for energy storage},
      volume       = {677},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2025-04204},
      isbn         = {978-3-95806-858-2},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {xviii, 169},
      year         = {2025},
      note         = {Dissertation, RWTH Aachen University, 2025},
      abstract     = {The transition to clean energy systems relies on advanced
                      energy storage technologies, such as lithium-ion and
                      solid-state batteries. In this realm, high-entropy materials
                      (HEMs) have been attracting significant attention due to
                      their potential to increase the energy density of electrodes
                      and improve the ionic conductivity and stability of solid
                      electrolytes. Atomistic simulations are a powerful tool to
                      understand the fundamental behavior of HEMs and accelerate
                      their design process. However, the complex ionic and
                      electronic structures of these materials introduce
                      substantial computational challenges. This dissertation
                      addresses these challenges by advancing computational
                      methodologies for modeling and understanding of HEMs. The
                      scope of the thesis is to (1) benchmark and apply
                      state-of-the-art electronic structure calculation methods
                      such as the DFT+U method with Wannier functions (WF) as
                      projectors, (2) investigate different techniques for
                      realistic modeling of ionic configurations of HEMs and (3)
                      to understand the performance of HEMs considered for battery
                      applications with joint atomistic simulations and
                      experimental investigation. Firstly, the DFT+U(WF)
                      methodology was benchmarked for conventional electrode
                      materials and extended to simple HEMs. This methodology was
                      shown to improve the accuracy of electronic structure
                      predictions compared to standard DFT+U, providing reliable
                      estimates of oxidation states and band gaps that are
                      comparable to computationally expensive hybrid functionals,
                      while maintaining computational efficiency. Secondly,
                      thermodynamic and electrochemical degradation mechanisms in
                      Li-rich HEM cathodes were investigated together with
                      experiments done by experimental collaborators, revealing
                      critical pathways such as oxygen dimer formation, transition
                      metal migration, and secondary phase formation. These
                      findings highlight the limitations of the high-entropy
                      effect and underscore the influence of local atomic
                      environments in de-stabilizing electrochemically active
                      phases. The research was further extended to garnet-based
                      solid electrolytes, for which the impact of configurational
                      entropy and atomic distributions on ionic conductivity and
                      structural stability was analyzed. Increasing dopant
                      diversity was shown to stabilize cubic phases with
                      higher-ionic conductivity over tetragonal phases. A
                      computationally derived high-entropy garnet with improved
                      ionic conductivity was successfully synthesized by
                      experimental colleagues at reduced synthesis temperatures.
                      Studies were extended to high-entropy fluorides and Prussian
                      white and blue analogs for diverse energy storage and
                      electronic applications, such as sodium-ion batteries and
                      memristors, showcasing the versatility of HEMs. Both
                      computational and experimental results indicate that
                      entropy-driven phase stabilization in these systems enhances
                      their cycling performance. Additionally, we proposed a
                      resistive switching mechanism for non-volatile memristors
                      composed of HEMs, which was verified through atomistic
                      simulations and experiments. Finally, advanced computational
                      techniques were introduced to address challenges in the
                      modeling of ionic configurations in disordered materials. In
                      a pioneering work, quantum annealing was successfully
                      applied to optimize ionic arrangements driven by Coulomb
                      energy. Additionally, the persistence of short-range order
                      (SRO) in disordered materials was revealed by calculating
                      the Warren-Cowley SRO parameters and radial distribution
                      function (RDF) analysis in a well-mixed four-component
                      phosphate system, emphasizing the need to incorporate SRO
                      into structural models of HEMs for more realistic modeling.
                      In summary, this dissertation addresses fundamental
                      challenges in understanding disordered systems at an
                      atomistic level. Computational approaches that have been
                      proposed lead to more accurate descriptions of electronic
                      structures and provide insights into how ionic arrangements
                      influence material properties. The results build a solid
                      basis for accurate computational studies of complex
                      disordered materials for next-generation energy storage
                      applications and could serve as the foundation for further
                      research into accurate and computationally feasible
                      approaches for modeling HEMs and other multi-component
                      systems, contributing to the broader advancement of energy
                      materials research.},
      cin          = {IET-3},
      cid          = {I:(DE-Juel1)IET-3-20190226},
      pnm          = {1221 - Fundamentals and Materials (POF4-122)},
      pid          = {G:(DE-HGF)POF4-1221},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      doi          = {10.34734/FZJ-2025-04204},
      url          = {https://juser.fz-juelich.de/record/1047287},
}