Co-adsorption of O_2 and H_2O on α-uranium(110) surface:A density functional theory study

First-principles calculations based on density functional theory corrected by Hubbard parameter U(DFT+U) are applied to the study on the co-adsorption of O2 and H_2O molecules to α-U(110) surface. The calculation results show that DFT+U method with Ueff= 1.5 e V can yield the experimental results of lattice constant and elastic modulus of α-uranium bulk well. Of all 7 low index surfaces of α-uranium, the(001) surface is the most stable with lowest surface energy while the(110) surface possesses the strongest activity with the highest surface energy. The adsorptions of O_2 and H_2O molecules are investigated separated. The O_2 dissociates spontaneously in all initial configurations. For the adsorption of H_2O molecule,both molecular and dissociative adsorptionsoccur. Through calculations of co-adsorption, it can be confirmed that the inhibition effect of O_2 on the corrosion of uranium by water vapor originates from the preferential adsorption mechanism,while the consumption of H atoms by O atoms exerted little influence on the corrosion of uranium.     

冠醚化合物在色谱分析中的应用

冠醚化合物都具有不同孔径的环,它不仅能够作为相转移催化剂、选择性电极、络合不同直径的无机离子,而且还可以作为液相色谱和气相色谱的固定液,分离分析无机化合物和有机化合物。利用旋光性冠醚化合物可以分离α-氨基酸等旋光性物质。本文使用不同类型的冠醚化合物     

O2、CO2和H2O在UN（001）表面化学吸附的密度泛函理论研究

采用广义梯度近似GGA,修正Perdew—Burke—Ernzerhof交换-关联泛函,以及周期性切片模型对O2、CO2和H2O在UN（001）表面的化学吸附行为进行非白旋极化水平的密度泛函理论计算．在四个对称性化学位置条件下,对化学吸附能与分子和UN（001）表面之间距离的关系曲线进行优化．结果表明O2、CO2和H2O分子的最稳定吸附位置分别为桥式平行、空心平行和桥式H向上,化学吸附能分别为14．127、4．421和5．736kJ／mol．从吸附物UN（001）表面角度考虑,O2与UN（001）表面之间的相互作用最高,然后为CO2和H2O,表明这些相互作用与吸附物的晶体结构相关．O2化学吸附导致UN（001）表面的N原子向基体内部迁移,而CO2和H2O化学吸附对UN（001）表面分别具有中等和忽略不计的效应．计算获得的态密度显示了化学吸附分子S、P轨道和U6d、U5f轨道之间的电子电荷转移行为．     

Interactions between vacancies and prismatic Σ3 grain boundary in α-Al_2O_3:First principles study

Interactions between vacancies and Σ3 prismatic screw-rotation grain boundary in α-Al_2O_3 are investigated by the first principles projector-augmented wave method.It turns out that the vacancy formation energy decreases with reducing the distance between vacancy and grain boundary(GB) plane and reaches the minimum on the GB plane(at the atomic layer next to the GB) for an O(Al) vacancy.The O vacancy located on the GB plane can attract other vacancies nearby to form an O–O di-vacancy while the Al vacancy cannot.Moreover,the O–O di-vacancy can further attract other O vacancies to form a zigzag O vacancy chain on the GB plane,which may have an influence on the diffusion behavior of small atoms such as H and He along the GB plane of α-Al_2O_3.     

First-principles study of co-adsorption behavior of O2and CO2molecules onδ-Pu(100)surface

First principles calculation is performed to study the co-adsorption behaviors of O₂and CO₂onδ-Pu(100)surface by using a slab model within the framework of density functional theory(DFT).The results demonstrate that the most favorable co-adsorption configurations are T_v-C₄O₇and T_p1-C₂O₈,with adsorption energy of-17.296 e V and-23.131 e V for CO₂-based and O₂-based system,respectively.The C and O atoms mainly interact with the Pu surface atoms.Furthermore,the chemical bonding between C/O and Pu atom is mainly of ionic state,and the reaction mechanism is that C 2 s,C 2 p,O 2s,and O 2p orbitals overlap and hybridize with Pu 6 p,Pu 6 d,and Pu 5 f orbital,resulting in the occurrence of new band structure.The adsorption and dissociation of CO₂molecule are obviously promoted by preferentially occupying adsorbed O atoms,therefore,a potential CO₂protection mechanism for plutonium-based materials is that in CO₂molecule there occurs complete dissociation of CO₂→C+O+O,then the dissociated C atom combines with O atom from O₂dissociation and produces CO,which will inhibit the O₂from further oxidizing Pu surface,and slow down the corrosion rate of plutoniumbased materials.     

O2、 CO2和H2O在UN(001)表面化学吸附的密度泛函理论研究

采用广义梯度近似GGA,修正Perdew-Burke-Ernzerhof交换-关联泛函,以及周期性切片模型对O₂、CO₂和H₂O在UN(001)表面的化学吸附行为进行非自旋极化水平的密度泛函理论计算. 在四个对称性化学位置条件下,对化学吸附能与分子和UN(001)表面之间距离的关系曲线进行优化. 结果表明O₂、CO₂和H₂O分子的最稳定吸附位置分别为桥式平行、空心平行和桥式H     

用MC方法计算铅玻璃对核材料γ射线的屏蔽作用(已撤稿)

核材料辐射出的γ射线对人体有很强的辐射损伤, 实际工作中多用铅玻璃对其进行屏蔽。 以甲状腺为研究对象, 应用蒙特卡罗方法通用软件MCNP4B程序建立模型, 模拟计算了操作人员在操作核弹头时, 弹头中产生的γ射线透过各种厚度的铅玻璃时人体甲状腺吸收剂量率。 结果表明, 铅玻璃确有良好的降低γ射线吸收剂量率的作用。
The γ ray which is radiated from a nuclear material can cause serious radiation damage to human organs, so lead glass are often used as a shielding material. In this paper, thyroid was the subject investigated. A mathematical model was established by using the general software code MCNP4B. We have calculated a series of thyroid’s absorbed dose rate when the γ ray which was generated from the warhead penetrated the various depths of the lead glass via the model. The results indicate that lead glass work well as a protector against γ rays.     

铀的原子模型

在U价电子采用(5s4p3d4f)/[3s3p2d2f]收缩基函数,原子实采用相对论原子实势进行处理的条件下,通过B3LYP杂化交换-相关泛函对U₂分子的电子态和势能数据进行了第一性原理计算．结果表明U₂分子的基态电子态为X⁹∑⁺_g ．同时用Murrell-Sorbie解析势能函数对对势数据进行拟合．在自旋极化水平和广义梯度近似下,采用密度泛函理论(DFT)和Perdew-Burke