Science and Technology on Surface Physics and Chemistry Laboratory , Mianyang 621908 , Sichuan , People's Republic of China.
Inorg Chem. 2019 Apr 1;58(7):4350-4364. doi: 10.1021/acs.inorgchem.8b03497. Epub 2019 Mar 13.
As impurities are virtually impossible to exclude from Pu oxides in realistic environments, understanding the roles of impurities is crucial for the applications and designs of Pu oxides. Here we perform a systematic first-principles DFT + U calculation to find the trends of transition-metal (TM) behaviors in PuO in terms of energetics, atomic properties, oxidation states, and electronic structures. The results show that group IV-B elements Ti, Zr, and Hf are energetically and electronically favorable in PuO and render the possibilities of forming Pu-TM-O ternary phases. In contrast, the remaining TMs tend to destabilize PuO and whether phase segregation or transition occurs largely depends on the redox conditions: oxidation one induces segregation, whereas reduction one facilitates the transition from PuO to PuO. On the basis of the correlations between the properties of TMs and their relative stabilities in PuO, we conclude that the degree of electron match between TMs and Pu plays the decisive role in the stability, as established for the cases of tetravalent elements, whereas some electron-mismatched but energetically stable TMs such as III-B and V-B elements could drive the valence transition of Pu, resulting in the phase instability of PuO.
由于在实际环境中几乎不可能将杂质从 Pu 氧化物中排除，因此了解杂质的作用对于 Pu 氧化物的应用和设计至关重要。在这里，我们进行了系统的第一性原理 DFT + U 计算，以根据能量学、原子性质、氧化态和电子结构来研究过渡金属（TM）在 PuO 中的行为趋势。结果表明，第 IVB 族元素 Ti、Zr 和 Hf 在 PuO 中具有能量和电子优势，并使形成 Pu-TM-O 三元相的可能性增加。相比之下，其余的 TM 倾向于使 PuO 不稳定，是否发生相分离或转变主要取决于氧化还原条件：氧化会引起分离，而还原则有利于 PuO 向 PuO 的转变。基于 TM 的性质与其在 PuO 中的相对稳定性之间的关系，我们得出结论，TM 与 Pu 之间的电子匹配程度在稳定性中起着决定性作用，这已在四价元素的情况下得到证实，而一些电子不匹配但能量稳定的 TM，如 III-B 和 V-B 族元素，可能会导致 Pu 的价态转变，从而使 PuO 的相不稳定。
