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Toward an improved solid-state Li electrolyte: A first-principles investigation of the structure, Li-ion migration pathways, and ionic conductivity of Li7La3Zr2O12 Raju, Muhammad Mozammal Kamal Han, Yulun Kilin, Dmitri Ding, Yi Zhang, Qifeng Activation energy Ionic conductivity Molecular dynamics (MD) Radial distribution function Density functional theory (DFT) Lithium lanthanum zirconium oxide (LLZO) Among solid state electrolytes, garnet-type Li7La3Zr2O12 (LLZO) has attracted considerable attention due to its high electrochemical stability, safety, and compatibility with lithium metal anodes. However, its lithium-ion conductivity strongly depends on the crystal structure: the tetragonal phase exhibits a significantly lower ionic conductivity than the cubic phase. In this work, first-principles density functional theory (DFT) and ab initio molecular dynamics (AIMD) are employed to systematically investigate the crystallographic structure, lithium-ion migration pathways, and ionic conductivity of both tetragonal and cubic LLZO. Lithium ion trajectories were analysed to determine diffusion coefficients over a wide temperature range. Activation energies are extracted from Arrhenius behaviour, and room-temperature ionic conductivities are extrapolated from high-temperature simulations. The results reveal that cubic LLZO possesses an intrinsically disordered lithium sublattice with abundant vacant sites and shorter migration pathways, which significantly enhance lithium-ion mobility. Consequently, the extrapolated room temperature ionic conductivity of cubic LLZO reaches the order of ~10-3 S/cm, in good agreement with experimental reports, while tetragonal LLZO exhibits much lower conductivity. This study provides atomistic-level insight into lithium diffusion mechanisms in LLZO and offers guidance for designing high-performance garnet-type solid electrolytes through structural disorder and vacancy engineering. Atlanta Publishing House LLC 2026-06-30 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion application/pdf application/pdf https://www.eurjchem.com/index.php/eurjchem/article/view/2759 10.5155/eurjchem.17.2.125-137.2759 European Journal of Chemistry; Vol. 17 No. 2 (2026): June 2026; 125-137 2153-2257 2153-2249 eng https://www.eurjchem.com/index.php/eurjchem/article/view/2759/3033 https://www.eurjchem.com/index.php/eurjchem/article/view/2759/3034 Copyright (c) 2026 Muhammad Mozammal Kamal Raju, Yulun Han, Dmitri Kilin, Yi Ding, Qifeng Zhang https://creativecommons.org/licenses/by-nc/4.0