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(3x2)riO2(110)完整表面上的吸附行为.另外,在本文给出的所有覆j盖度模式下(θ=1/6-1 ML),我们仪研究其基态构型.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.%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.
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