كيف تتدفق أيونات الهيدروجين عبر بلورة صلبة سريع

الملخص الأصلي

كما كتبه المؤلفون، بالإنجليزية arXiv:2603.00852

We performed muon spin rotation and relaxation ($$\mu$$SR) experiments to investigate the microscopic mechanism behind the high ionic conductivity ($$\sigma$$) exhibited by hydride (H$$^-$$) ions in lanthanum hydroxide LaH$$_{3-2x}$$O$$_x$$. The $$\mu$$SR spectra observed at 5--300 K in a sample with $$x\approx0.25$$ consist primarily of two components which are attributed to muons occupying tetrahedral (Tet) and octahedral (Oct) sites common to H$$^-$$. The spectra also indicate that muons at the Oct sites (Mu$$_{\rm O}$$) appear nearly stationary in the time scale of $$\mu$$SR ($$\sim$$10$$^{-5}$$ s), whereas those at the Tet sites (Mu$$_{\rm T}$$) are subject to the fluctuating local fields. The cusp-like peak in the fluctuation rate around 160 K and the decrease in linewidth at higher temperatures probed by Mu$$_{\rm T}$$ suggest that the jump motion of both Mu$$_{\rm T}$$ (via the vacant Oct sites) and surrounding Oct-site H$$^-$$ contributes to spin relaxation and that the fluctuation frequency is widely distributed. These results indicate that the implanted Mu behave as Mu$$^-$$ and that the jump motion of Mu$$^-$$/H$$^-$$ is restricted by the availability of nearby vacant sites. On the other hand, the activation energy for the jump is estimated to be 0.11(3) eV, which is significantly different from $$\sim$$1.3 eV evaluated from the temperature dependence of $$\sigma$$ at high temperatures ($$\gtrsim400$$ K). In our attempt to resolve this discrepancy, we discuss problems inherent in interpreting $$\sigma$$ using the Arrhenius equation, and demonstrate that the behavior of H$$^-$$ ions can be better explained as a viscous fluid exhibiting a glass transition.