Density functional embedded cluster study of Cu(4), Ag(4) and Au(4) species interacting with oxygen vacancies on the MgO(001) surface.
Density functional embedded cluster study of Cu(4), Ag(4) and Au(4) species interacting with oxygen vacancies on the MgO(001) surface.
复制标题
Cu(4)、Ag(4) 和 Au(4) 物质与 MgO(001) 表面氧空位相互作用的密度泛函嵌入团簇研究。
作者：
Konstantin M. Neyman;Chan Inntam;L. Moskaleva;N. Rösch
采用密度泛函方法和先进的嵌入模型研究了Cu（4）、Ag（4）和Au（4）物种吸附在MgO（001）表面上的中性（F（s））和带电（F（s）（+））氧空位.气相菱面结构的钴金属四聚体是只有适度的吸附影响。在最稳定的表面构型中，四聚体的平面垂直于MgO（001）表面取向;一个金属原子连接到氧空位，另一个连接到附近的表面氧阴离子。最近在无缺陷的MgO（001）上发现了非常相似的结构基序，其中两个O（2-）离子作为吸附位点。遵循与规则MgO（001）表面相互作用的趋势，Au（4）和Cu（4）与F（s）和F（s）（+）位的结合显著强于Ag（4）。在氧空位处，特别是在F（s）处，这种较强的吸附相互作用部分是由于吸附物上电子密度的显著积累。我们还研究了小的支持的金属物种聚集到吸附的二，三和四聚体的倾向。此外，我们证明了核心水平的电离势提供了检测实验支持的金属四聚体和表征它们的结构与计算数据的帮助下的可能性。
Cu(4), Ag(4), and Au(4) species adsorbed on an MgO(001) surface that exhibits neutral (F(s)) and charged (F(s) (+)) oxygen vacancies have been studied using a density functional approach and advanced embedding models. The gas-phase rhombic-planar structure of the coinage metal tetramers is only moderately affected by adsorption. In the most stable surface configuration, the plane of the tetramers is oriented perpendicular to the MgO(001) surface; one metal atom is attached to an oxygen vacancy and another one is bound to a nearby surface oxygen anion. A very similar structural motif was recently found on defect-free MgO(001), where two O(2-) ions serve as adsorption sites. Following the trend of the interactions with the regular MgO(001) surface, Au(4) and Cu(4) bind substantially stronger to F(s) and F(s) (+) sites than Ag(4). This stronger adsorption interaction at oxygen vacancies, in particular at F(s), is partly due to a notable accumulation of electron density on the adsorbates. We also examined the propensity of small supported metal species to aggregate to adsorbed di-, tri- and tetramers. Furthermore, we demonstrated that core-level ionization potentials offer the possibility for detecting experimentally supported metal tetramers and characterizing them structurally with the help of calculated data.