CO在α-U(001)表面的吸附

采用密度泛函理论中的广义梯度近似,计算了CO在α-U(001)表面的吸附、解离和扩散.结果表明:CO分子以CU3OU2构型化学吸附在α-U(001)表面,吸附能为1.78-1.99eV;吸附后表层U原子向上迁移,伴随着褶皱的产生;CO分子与表面U原子的相互作用主要是U原子的电子向CO分子最低空轨道2π*转移,以及CO2π*/5σ/1π-U6d轨道间杂化而生成新的化学键;CO解离吸附较分子吸附在能量上更为有利,h1(C)+h2(O)和h1(C)+h1(O)(h:空位)解离态吸附能分别为2.71和3.08eV;近邻三重穴位之间C、O原子的扩散能垒分别为0.57和0.14eV,预示O原子较C原子更易在U(001)表面扩散迁移.

CO Adsorption on α-U(001) Surface

The adsorption, dissociation, and diffusion of CO on the α-U(001) surface were studied using density functional theory with the generalized gradient approximation (GGA). The calculation results show that a CU3OU2-type molecular chemisorption of CO is favored with adsorption energies of 1.78-1.99 eV. The U atoms of the surface layer are found to move upwards after adsorption coupled with a rumpling of the surface layer. The interaction between the U atoms and a CO molecule results mainly from the population of the CO 2π* LUMO by U electrons and the CO 2π*/5σ/1π-U 6d orbital hybridization. Dissociative adsorption is energetically more favored than molecular adsorption with adsorption energies of 2.71 and 3.08 eVfor the h1(C)+h2(O) and h1(C)+h1(O) (h: hollowsite) dissociative configurations, respectively. The diffusion barriers of C and O atoms between two adjacent threefold hollow sites are found to be 0.57 and 0.14 eV, respectively, which indicates that the on-surface diffusion ofO atoms is more easily achieved than that of C atoms.