论文标题
PD的低索引表面的表面和地下空位处的氢捕获
Hydrogen trapping at surface and subsurface vacancies of low-index surfaces of Pd
论文作者
论文摘要
在密度功能理论（DFT）方法中研究了（111）和（100）PD表面的表面和（100）表面的表面层的氢分离。计算了空缺下H原子的各个簇的吸附能和构型。在空缺中的不同位点的吸附能从-0.26 eV（接近散装群集的距离）到-0.62 eV。在地下层中空位产生的孔中的位点上方发现了增强的结合。对于（111）表面空置空缺，最有利的隔离是四面体晶格位点，而对于（100）八角位的结合能具有较高的结合能。 （111）表面的晶格松弛效应很小，但对于（100）表面而言明显增强。氢向表面层空位的分离伴随着最小的电荷转移，这表明了群集构型。在高表面覆盖范围内，由于H种族隔离而导致的簇形成能量的降低应导致地下空位簇的浓度大大扩大，而由于盛行的表面吸附，表面仍未受到损坏。
Hydrogen segregation to vacancies in the surface and subsurface layers of (111) and (100) surfaces of Pd is studied in the density functional theory (DFT) approach. Adsorption energies and configurations of various clusters of H atoms at the vacancies are calculated. The adsorption energy varies for different sites in the vacancies with the distance to the surface from -0.26 eV (close to that of the bulk clusters) to -0.62 eV. Enhanced binding is found for the sites above the pores produced by vacancies in the subsurface layer. For the (111) surface vacancy the most favorable for segregation are tetrahedral lattice sites, while for (100) octa-sites have higher binding energy. Lattice relaxation effects are minor for the (111) surface but noticeably enhanced for the (100) surface. Hydrogen segregation to surface layer vacancies is accompanied with minimal charge transfer, which shows itself in cluster configurations. At high surface coverage the reduction of the cluster formation energy due to the H segregation should result in strongly enlarged concentration of the subsurface vacancy clusters, while the surface remains undamaged due to the prevailing surface adsorption.
