2026-10-14T07:46:09Z https://api.figshare.com/v2/oai

oai:figshare.com:article/32414772 2026-09-30T20:26:13Z category_1 category_915 category_7 category_873 category_931 category_64 category_106 category_135 portal_87 item_type_3 month_year_09_2026

Not all H atoms contribute to low activation barrier diffusion in Ba_1.75LiH_2.7O_0.9 Yoyo Hinuma (1270065) Biophysics Physical Sciences not elsewhere classified Medicine Chemical Sciences not elsewhere classified Information Systems not elsewhere classified Cancer Science Policy Computational Biology Superionic conductivity tracer diffusion coefficient molecular dynamics neural network potential Ba1.75LiH2.7O0.9 <p>Superionic conductors have extremely high conductivity in some constituent ions even in the solid state, and many lose their superionicity below a critical temperature. The conductivity of K₂NiF₄ structure-based Ba_1.75LiH_2.7O_0.9 jumps over three orders of magnitude at ~ 573 K. This jump is not at a first-order structural phase transition temperature. Molecular dynamics (MD) simulations using a density functional theory (DFT) trained universal neural network potential (NNP) were conducted in this study. The Arrhenius plot of the tracer diffusion coefficient is a straight line between 455 and 741 K, inconsistent with the conductivity jump. The 3D activation barrier is ~0.3 eV, which is much lower than typical K₂NiF₄ structure-based oxyhydrides. The features in the radial distribution function are almost temperature independent. However, statistical inspection of the tracer diffusion coefficient for each atom, which is very difficult with DFT-MD but is feasible with NNP-MD, revealed the existence of effectively immobile H atoms over the entire studied temperature range. Most H do not engage in concerted migration, according to a comparison with a universal curve for independent random walkers. These findings hold for all phases, which have different distributions of Li, O, and H atoms in the same structural framework. Incorporating many vacancies, especially in ‘K’ sites of the K₂NiF₄ framework, could form a low activation barrier H diffusion network not available in conventional oxyhydrides with the same framework. Gaining access to such a percolating network above a certain temperature can explain the superionic transition at this temperature.</p> <p>Neural network potential molecular dynamics show that the superionic transition in H⁻-conductor Ba_1.75LiH_2.7O_0.9 that does not accompany a structural transition is caused by changes in non-migrating H with temperature.</p> 2026-09-30T20:26:13Z Dataset Dataset 10.6084/m9.figshare.32414772.v2 https://figshare.com/articles/dataset/Not_all_H_atoms_contribute_to_low_activation_barrier_diffusion_in_Ba_sub_1_75_sub_LiH_sub_2_7_sub_O_sub_0_9_sub_/32414772 CC BY