(Al_(16)Ti)^(n±)(n=0-3)离子团簇中Ti原子对电子结构及其与H_2O分子相互作用的显著影响

A Dramatic Influence of Ti Atom on the Electronic Structures of (Al_(16)Ti)^(n±)(n=0-3) Ionic Clusters and Their Interaction with H_2O Molecules

用密度泛函理论结合全电子自旋极化方法构建并优化出了最稳定的(Al16Ti)n±(n=0-3)离子团簇,研究了其几何结构、稳定性和电子结构.同时研究了水分子在(Al16Ti)n±(n=0-3)离子团簇表面的吸附结构和吸附能.研究结果与纯(Al17)n±(n=0-3)离子团簇的电子结构及其与H2O分子的相互作用规律做了对比.通过电子最高占据轨道和最低空轨道的空间分布,发现大部分的活性电子占据在Ti原子位置,少量电子根据曲率从大到小的顺序依次占据.通过分析最稳定的(Al16Ti H2O)n±(n=0-3)吸附化合物的几何结构可以看出,水分子都倾向于吸附在Ti原子上,并且为亲氧吸附.在所有的吸附化合物中,(Al16Ti H2O)+具有最短的平均O―H键长,比孤立H2O分子中的O―H键约长0.0003 nm,然后随着电子数的增加或减少,O―H键都会进一步被拉长.研究结果表明,Al团簇离子中Ti原子的掺杂可以有效提高H2O分子的解离效率.另外,在金属团簇的几何结构效应与杂质效应共同出现时,杂质的影响占据了主导地位.

The most stable （Al16Ti）n± （n=0-3） ions were modeled and optimized using density functional theory combined with al-electron spin-polarized calculations. The geometries, stabilities, and electronic structures of the （Al16Ti）n ± （n=0-3） ionic clusters, as wel as the adsorption structures and adsorption energies of H2O molecules on the （Al16Ti）n± （n=0-3） ionic clusters, were studied. The results were compared with those obtained for pure （Al17）n± （n=0-3） ionic clusters. The spatial distributions of the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals for the （Al16Ti）n± （n=0-3） ionic clusters showed that the free electrons tend to occupy Ti sites. And a few residual free electrons would occupy sites with large curvatures. An extensive structure search was performed to identify the low-energy conformations of （Al16TiH2O）n± （n=0-3） complexes. Based on the geometries of the studied adsorption complexes, it was found that the most stable structures were＆amp;nbsp;prone to oxygen-based adsorption onto Ti atom. （Al16TiH2O）＋ion featured the shortest average O―H bond length, that was^0.0003 nm longer than that observed in isolated H2O molecule. The O―H bond length increased with either increasing or decreasing number of the electrons. The studies implied that Ti dopant in Al ionic clusters improved the dissociation efficiency of H2O molecules. Furthermore, the doping effect played a more important role than the geometry effect in determining the electronic structures of the （Al16Ti）n ionic clusters and their interaction with H2O molecules.