Chemical bonds and vibrational properties of ordered (U, Np, Pu) mixed oxides
Chemical bonds and vibrational properties of ordered (U, Np, Pu) mixed oxides
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DOI：
10.1063/1.4772671
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发表时间：
2013-01
影响因子：
3.2
通讯作者：
Yu Yang;Ping Zhang
中科院分区：
文献类型：
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作者：
Yu Yang;Ping Zhang
我们采用密度泛函理论+U方法研究了有序（U，Np，Pu）混合氧化物（MOXs）UNpO 4，NpPuO 4和UPuO 4的化学键特征和振动性质.结果表明，不同锕系元素的5 f电子态在三种MOX中都保持了各自的定域特征。不同锕系元素的5 f电子态不重叠，并且倾向于分布在其他锕系元素的5 f态的能带隙上。其结果是，三个有序MOX都显示出较小的带隙比那些组分二氧化物，与0.91，1.47，和0.19 eV的UNpO 4，NpPuO 4，和UPuO 4的值，分别。通过仔细的电荷密度分析，我们进一步表明，在MOX的U-O和Pu-O键比在UO 2和PuO 2显示更多的离子特性，而Np-O键比在NpO 2显示更多的共价特性。化学键中共价的变化导致MOX中不同的氧原子振动频率。
We use density functional theory +U to investigate the chemical bonding characters and vibrational properties of the ordered (U, Np, Pu) mixed oxides (MOXs), UNpO4, NpPuO4, and UPuO4. It is found that the 5f electronic states of different actinide elements keep their localized characters in all three MOXs. The occupied 5f electronic states of different actinide elements do not overlap with each other and tend to distribute over the energy band gap of the other actinide element's 5f states. As a result, the three ordered MOXs all show smaller band gaps than those of the component dioxides, with values of 0.91, 1.47, and 0.19 eV for UNpO4, NpPuO4, and UPuO4, respectively. Through careful charge density analysis, we further show that the U-O and Pu-O bonds in MOXs show more ionic character than in UO2 and PuO2, while the Np-O bonds show more covalent character than in NpO2. The change in covalencies in the chemical bonds leads to vibrational frequencies of oxygen atoms that are different in MOXs.