中文摘要：

采用自旋极化密度泛函和广义梯度近似的方法并结合周期平板模型, 探讨了不同覆盖度（θ）下双金 属簇X （X=Pt-Au, Au-Au）在（3×2）TiO2（110）完整表面上的吸附行为. 另外, 在本文给出的所有覆盖度模式下（θ= 1/6-1 ML）, 我们仅研究其基态构型. 计算结果表明： 当θ〈1/2 ML时, 金属簇X在TiO2（110）表面上吸附能随覆盖 度的增加而增加; 当θ〉1/2 ML时, 除了饱和覆盖度下, 吸附能随覆盖度的增加而减小; 当θ=1/2 ML时, 吸附能最 大. 即使Pt-Au/TiO2体系的吸附能比Au-Au/TiO2体系的小, 但相对于Au-Au 簇, Pt-Au 簇更容易在TiO2（110）表 面上形成双金属单分子层. 在半覆盖和全覆盖下, X簇的峰与TiO2的峰在-3.0 eV到费米能级之间产生明显重 叠, 表明簇与底物之间存在化学作用. 且当覆盖度小时, X-TiO2相互作用是成簇的主要因素; 随着覆盖度的增 大, X-X原子间相互作用就逐渐变成了成簇的主要动力.

英文摘要：

Based on spin-polarized density functional theory and generalized gradient approximation （DFT-GGA） calculations, the coverage-dependent adsorption of X bimetallic clusters （X=Pt-Au, Au-Au） on the （3 × 2） TiO2（110） surface has been investigated utilizing periodic supercell models in the absence of oxygen vacancy sites. Only the ground-state structures corresponding to the given coverage patterns （θ= 1/6-1 ML） for X clusters are discussed in this work. The unambiguous results reveal that the adsorption energies increase with coverage up to 1/2 ML and then decrease except for when saturated coverage is reached. According to the interaction with X clusters, it is more feasible at all coverage levels to create a monolayer film of Pt-Au bimetallic clusters on the TiO2（110） surface than it is to create a monolayer of Au- Au clusters, even though the adsorption energy of the Pt-Au/TiO2 adsorption system is smaller in comparison with that of the Au-Au/TiO2 system. Importantly, especially for the half and saturated coverages, there is a broadening of X peaks overlapping with the TiO2 state ranging from -3.0 eV to the Fermi level, suggesting a strong interaction between the surface and bimetallic cluster. Also of particular interest is the adsorptive mechanism where the X-TiO2 interaction is the main driving force at the initial stage of the adsorption process, whereas the X-X interaction controls the process as the coverage increases.