Regensburg 2025 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 14: Poster

KFM 14.6: Poster

Wednesday, March 19, 2025, 17:00–18:30, P1

Investigation of hydrogen diffusion in LiNbO₃ and LiTaO₃ from density-functional theory — •Christa Fink and Simone Sanna — Institute for Theoretical Physics, Justus-Liebig-University, Heinrich-Buff-Ring 16, 35392 Giessen, Germany

Hydrogen is always present in LiNbO₃ and LiTaO₃ crystals. Therefore, the lattice locations of hydrogen within the crystal as well as its diffusion and mobility have been a matter of research for many years. While the energetically most favorable positions of hydrogen within the atomic lattice have been investigated intensely, there exist less investigations of diffusion paths and energy barriers. To fully understand the diffusion of hydrogen in LiNbO₃, LiTaO₃ and their solid solutions, we calculate energy barriers and three-dimensional minimum energy paths for hydrogen diffusion using the nudged elastic band method based on density-functional theory as implemented in VASP [1, 2]. Starting from the energetically most favorable position, we calculate minimum energy paths through the crystal towards the next equivalent position. We extend our calculations from the stoichiometric material to crystals with Lithium vacancies, which are the most common defects in LN and LT, for a better comparison to experimental results [3, 4].

[1] G. Kresse, J. Furthmüller, Computational Materials Science 6, 15 (1996). [2] G. Kresse, J. Furthmüller, Phys. Rev. B 54, 11169 (1996). [3] Kofahl, C. et al., Defect and Diffusion Forum, 429, 136-143 (2023). [4] Kofahl, C. et al., Solid State Ionics 403, 116383 (2023).

Keywords: Lithium Niobate; Lithium Tantalate; Density-functional theory; Hydrogen Diffusion; Nudged elastic band method