CF_2在Au团簇上吸附的密度泛函理论研究

Density Functional Theory Study about Difluorocarbene Adsorption on Au Clusters

应用密度泛函理论B3LYP方法研究单重态CF2在Aun-(n=1～5)和Au3、Au3+、Au3-团簇上的吸附行为.结果表明:Au与C在同一平面形成Au-C键,属于化学吸附;随着n的增加,吸附能减小,团簇尺寸增大吸附作用减弱,且n为奇数时团簇的吸附能大于n为偶数时团簇的吸附能,呈奇偶变化规律.C-F键长也有相同的变化趋势;LUMO和HOMO轨道能隙随n的增大呈减小趋势,团簇稳定性减弱;CF2在Au3-上的吸附最强,Au3+次之,Au3最弱;Au3-吸附后C-F键长增加明显,Au3+次之,Au3变化不明显.Au团簇的电性对吸附作用影响较大,Au3+、Au3-可以活化CF2.

The adsorption behaviors of difluorocarbene on Aun- （n= 1-5） clusters and anionic, neutral, cationic Au3 clusters are systematically investigated by Density Functional Theory （DFT）. The adsorption of CF2 on the Aun- （n=1-5） clusters manifests that the Au and C are in the same plane, has formed Au-C bond,and are chemical adsorption. The adsorption energy of the clusters are tend to decrease with the increasing of Au atom number. The adsorption effect becomes weaken due to the size of Au-clusters expanding. The adsorption energies in odd-numbered Au.CF2- clusters are relatively higher than that in adjacent even-numbered Au.CF2- clusters. This odd-even oscillation is observed in the variations of C-F bond-lengths,too. The gaps between LUMO and HOMO orbits of CF2Aun- clusters decrease with the Au atom n increasing. The adsorption is the first for the CF2 ：on Au3-, the second on the Au3＋ , for the last on Au3＋ The trend of the C- F bond lengths for CF2 ： adsorption on Au3- ,Au3＋ , and Au3 is similar to that of the adsorption. The charge of Au clusters plays an important role in adsorption of CF2 ： on Au3 clusters, CF2 ：is activated on Au3- and Au3＋.