AI 中文总结
本文通过第一性原理计算揭示氢化镍酸盐钙钛矿中极化子介导的金属-绝缘体转变机制，明确其质子传导特性，为筛选电解质材料及提升质子传导率提供理论指导。
AI 中文摘要
镍基钙钛矿因具有自发吸氢特性，且氢化后电阻率显著升高，已成为质子传导型燃料电池电解质的候选材料。然而，稀土镍酸盐中氢诱导的金属-绝缘体转变（MIT）机制仍存在争议，特别是掺杂电子是占据Ni e$_g$态还是O 2p配体空穴态。本文通过对NdNiO$_3$的第一性原理计算揭示了完整的MIT机制：氢掺杂引入的电子占据Ni-O杂化d$_8$L构型的O 2p配体空穴态，促进电子极化子形成；生成的电子极化子与质子极化子共同削弱Ni-O杂化，使原本巡游的Ni e$_g$电子局域化，形成局域d8（t$_{2g}$$^6$e$_g$$^2$）电子构型，引发莫特转变。此外，研究发现，与NdNiO$_3$相比，A位离子半径更小的SmNiO$_3$更易吸氢，但质子扩散能力更弱；氢化通过八面体内转移促进质子沿[001]方向渗透，但整体质子扩散率降低。这些结果为实验筛选强关联氧化物电解质材料提供指导，也为提高稀土镍酸盐的质子传导率提供理论见解。
英文摘要
Nickel-based perovskites, owing to their spontaneous hydrogen uptake and the dramatic increase in resistivity upon hydrogenation, have emerged as promising candidates for proton-conducting fuel cell electrolytes. However, the mechanism of the hydrogen-induced metal-insulator transition (MIT) in rare-earth nickelates remains under debate, particularly regarding whether the doped electrons occupy Ni e$_g$ states or O 2p ligand hole states. Here, we reveal a comprehensive MIT mechanism using first-principles calculations on NdNiO$_3$: the electrons introduced by hydrogen doping occupy the O 2p ligand hole states of the Ni-O hybridized d$_8$L configuration, promoting electron-polaron formation. The resulting electron polarons, together with proton polarons, weaken the Ni-O hybridization and thereby drive the originally itinerant Ni e$_g$ electrons toward localization. This generates a local d8 (t$_{2g}$$^6$e$_g$$^2$) electronic configuration, leading to a Mott transition. In addition, we also find that compared with NdNiO$_3$, SmNiO$_3$ with a smaller A-site ionic radius more readily absorbs hydrogen but exhibits weaker proton diffusion capability. Hydrogenation promotes proton permeation along the [001] direction via the intraoctahedral transfer, whereas the overall proton diffusivity is reduced. These results provide guidance for experimental screening of strongly correlated oxides as electrolyte materials and offer theoretical insights for enhancing proton conductivity in rare-earth nickelates.
