Intrinsic donor point defects and electron polarons are investigated in bulk ${\mathrm{AmO}}_2$ using density functional theory $+U$ calculations. Oxygen vacancies are deep double-donor defects, with transition energy levels closer to the valence band maximum than to the conduction band minimum. Americium interstitials are unlikely, due to prohibitive formation energies. Self-trapped electron polarons (which locally correspond to reducing one ${\mathrm{Am}}^{4+}$ in ${\mathrm{Am}}^{3+}$) are found extremely stable (self-trapping energy $=-1.01\mathrm{eV}$). The electron is even more stable in the self-trapped state (far from an oxygen vacancy) rather than in association with an oxygen vacancy, indicating that oxygen vacancies have the tendency to spontaneously ionize, and thus automatically liberate electron polarons in the lattice. This large stability of the electron polarons confines the accessible range of Fermi levels to a very narrow interval between the valence band maximum $E_{\text{VBM}}$ and $\sim E_{\text{VBM}}+0.09\mathrm{eV}$. In oxygen-poor conditions, oxygen vacancies may be formed in rather large concentration in ${\mathrm{AmO}}_2$ and have a strong probability to be doubly or singly ionized, with charge compensation being mostly ensured by a large number of electron polarons. The electron polaron hopping from an Am atom onto the nearest one involves a rather large activation energy of $\sim 0.6\mathrm{eV}$ and probably takes place by a nonadiabatic mechanism.

中文翻译：

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二氧化a中的电子极化子和施主点缺陷

大量研究了固有供体点缺陷和电子极化子 ${\mathrm{美国运通}}_2$ 使用密度泛函理论 $+ü$计算。氧空位是深的双供体缺陷，跃迁能级接近价带最大值，而不是导带最小值。由于形成能量过高，meric间隙不太可能出现。自陷电子极化子（局部对应于还原一个${\mathrm{上午}}^{4+}$ 在 ${\mathrm{上午}}^{3+}$）被发现非常稳定（自陷能量 $=-1.01\mathrm{电子伏特}$）。电子在自陷陷状态下（远离氧空位）更加稳定，而不是与氧空位结合，这表明氧空位具有自发电离的趋势，因此自动释放晶格中的电子极化子。电子极化子的这种大稳定性将费米能级的可及范围限制在价带最大值之间的非常窄的区间内${Ë}_{\text{VBM}}$ 和 $〜{Ë}_{\text{VBM}}+0.09\mathrm{电子伏特}$。在缺氧条件下，氧空位可能会以较高浓度形成。${\mathrm{美国运通}}_2$并极有可能被双电离或单电离，电荷补偿主要由大量电子极化子来保证。从Am原子跳到最近原子的电子极化子涉及相当大的活​​化能$〜0.6\mathrm{电子伏特}$ 并且可能是通过非绝热机制发生的。