Pt/Cu(001)-p(2×2)-O表面吸附结构的总能计算

采用密度泛函理论(DFT)研究了氧吸附后Pt/Cu(001)表面合金的原子结构和表面性质. 计算结果表明, 在Pt/Cu(001)-p(2×2)-O表面最稳定结构中, 衬底表面原子层不发生再构, 氧原子吸附于4重对称的Pt原子谷位, 每个氧原子吸附能约为2.303 eV. 吸附结构的Cu—O和Pt—O键键长分别为0.202和0.298 nm, 氧原子的吸附高度ZCu—O约为0.092 nm. 吸附前后Pt/Cu(001)-1ML(monolayer)表面合金的表面功函数分别为4.678和5.355 eV. 吸附表面氧原子和衬底的结合主要来自氧原子2p轨道和衬底金属原子d轨道的杂化作用, 氧原子吸附形成的表面电子态主要位于费米能级以下约-2.7 eV 处.

Total Energy Calculations on the Geometry Structure of Pt/Cu(001)-p(2×2)-O Surface

Density functional theory was used to determine the geometric structure and adsorption properties of Pt/Cu(001)-p(2×2)-O surface using ultra-soft pseudo-potential (USPP) methods. The calculation results indicated the Pt/Cu(001)-p(2×2)-O surface in favor of no reconstruction adsorbent model with oxygen atoms adsorbed on hollow sites above platinum atoms of the second layer. The adsorption energy of an oxygen atom is about 2.303 eV with respect to the oxygen molecule. The surface work function for this adsorbate-adsorbent system is estimated to be 5.355 eV. Bond lengths of Cu—O and Pt—O were calculated to be 0.202 and 0.298 nm, respectively. The adsorption height (ZCu—O) of oxygen atoms is about 0.092 nm. Surface electronic structures show that the cohesive effect between adsorbates and adsorbent is mainly due to the hybridization between metal d and oxygen 2p orbitals. The localized surface state is mainly generated at -2.7 eV below the Fermi energy EF.