“异卵双生”铁电性：基于第一性原理研究氢掺杂钐镍酸盐中的竞争极性态
"Fraternal-twin" ferroelectricity: competing polar states in hydrogen-doped samarium nickelate from first principles
AI总结：
本研究利用第一性原理计算发现，氢掺杂钐镍酸盐中局域电子转移至相邻八面体的势垒极低，导致极化剧变，由此提出“异卵双生”非常规铁电体概念。
摘要：
氢可逆嵌入钐镍酸盐SmNiO$_3$（SNO）近期备受关注。氢进入SNO后发生解离：H$^+$与氧结合，价电子局域在附近的NiO$_6$八面体上，产生局域偶极矩。本研究利用第一性原理计算，探讨了氢掺杂SNO在每Ni对应1/4氢浓度下的极性态。SNO固有的倾斜模式与间隙氢的存在，构成了将这些极性态反演切换至其对称相关态的不可逾越的能量势垒。我们发现，将局域电子转移至相邻NiO$_6$八面体的势垒足够低，该状态在对称性上无关，但在外延应变下能量相等，从而导致极化发生巨大变化。我们将这种非常规铁电体称为“异卵双生”铁电体。
英文摘要：
Reversible intercalation of hydrogen into samarium nickelate, SmNiO$_3$ (SNO), has been of recent interest. Upon entering SNO, the hydrogen dissociates: the H$^+$ binds to an oxygen and the valence electron localizes on a nearby NiO$_6$ octahedron, resulting in a local dipole moment. In this work, we use first-principles calculations to explore the polar states of hydrogen-doped SNO at a concentration of 1/4 hydrogen per Ni. The inherent tilt pattern of SNO and the presence of the interstitial hydrogen present an insurmountable energy barrier to switch these polar states to their symmetry-related states under inversion. We find a sufficiently low barrier to move the localized electron to a neighboring NiO$_6$ octahedron, a state unrelated by symmetry but equal in energy under epitaxial strain, resulting in a large change in polarization. We term this unconventional ferroelectric a "fraternal-twin" ferroelectric.
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