H2O分子在α-U(001)表面的吸附和解离

Adsorption and Dissociation of H2O Molecule on α-U(001) Surface

摘要:

采用广义梯度密度泛函理论研究了H2O分子在α-U(001)表面上的吸附、扩散和解离。 结果表明，H2O分子在α-U(001)表面的最稳定构型为平行于表面的顶位吸附结构，吸附能为0.58 eV。吸附作用主要源于H2O分子1b1轨道与表面U原子6d轨道的空间交叠，同时伴有弱的H2O 3a1-U 6d轨道交叠。近邻顶位间H2O分子的扩散能垒为0.20~0.23 eV，预示H2O分子易于在α-U(001)表面发生扩散迁移。OH+H解离吸附较分子吸附在能量上高1.24~1.39 eV，解离能垒为0.56~0.62 eV，预示一定热激活条件下，吸附H2O分子趋向解离形成OH基团和H原子

Abstract:

The adsorption, the diffusion and the dissociation of H2O molecule on α-U(001) surface have been studied using density functional theory (DFT) within generalized gradient approximation (GGA). The calculation results indicate that H2O molecule is preferentially adsorbed on the top site in a flat-lying configuration with the adsorption energy of 0.58 eV. The adsorption interaction is mainly contributed by the overlapping between the 1b1 orbital of H2O and the 6d orbital of the top-layer U atom, along with some weak H2O 3a1-U 6d mixing. The activation energy for H2O diffusion between two adjacent top sites is 0.20~0.23 eV, indicating that the on-surface diffusion is easy for H2O molecule. The OH+H dissociative adsorption is about 1.24~1.39 eV higher in energy than molecular adsorption, together with the dissociation barrier of 0.56~0.62 eV, suggesting that the dissociation of adsorbed H2O into OH and H can occur under the certain heat activation condition