Lithium superionic behavior and defect robustness in LiNbOCl
                    <sub>4</sub>
                    : a first-principles molecular dynamics study

Halimah Harfah; Yoshitaka Tateyama; Kazunori Takada; Randy Jalem

doi:10.1039/d5ta05478h

Journal article Lithium superionic behavior and defect robustness in LiNbOCl ₄ : a first-principles molecular dynamics study

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Halimah Harfah, Yoshitaka Tateyama, Kazunori Takada, Randy Jalem. Lithium superionic behavior and defect robustness in LiNbOCl ₄ : a first-principles molecular dynamics study. Journal of Materials Chemistry A. 2026, 14 (27), 17385-17401. https://doi.org/10.1039/d5ta05478h

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In this study, we systematically investigate Li-ion transport in pristine and LiCl Schottky-defected LiNbOCl4 using density functional theory molecular dynamics (AIMD). Pristine LiNbOCl4 demonstrates robust superionic behavior with low activation energy (0.236 eV) and high room-temperature conductivity (9.57 × 10−3 S cm−1), facilitated by a rigid Nb–O–Cl framework and a disordered Li sublattice. Introducing LiCl Schottky defects slightly increases the activation energy to 0.241 eV and slightly reduces conductivity to 8.20 × 10−3 S cm−1. While defects preserve global percolation networks and mechanical softness, they introduce localized structural disruptions at vacancy-adjacent polyhedra. Notably, the dynamic gating mechanism where coherent anion rotations transiently expand diffusion bottlenecks is impaired. Unlike the classical paddle-wheel mechanism involving rotating polyanion clusters, this mechanism describes a distinct mode of transient bottleneck expansion driven by coordinated motion of individual halide and oxide anions within an oxyhalide lattice. The disruption of this mechanism is reflected in the emergence of rotational incoherence, rapid bond angle decorrelation, attenuation of high-frequency O-based phonon modes (∼80 meV), and a strong reduction and spatial localization of anion reorientation events that are associated with enhanced Li-ion motion, as identified by event-triggered ensemble. Together, these effects suppress bottleneck breathing, limiting the transient widening of diffusion pathways and effectively increasing the migration barrier. Li space–time correlation analysis further reveals diminished temporal coherence and transport cooperativity in the defected structure.

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