分子氧在Co_(n)小团簇吸附的密度泛函研究

Density Functional Study of Molecular Oxygen Adsorbed on Co_(n) Small Clusters

采用基于密度泛函理论(DFT)的Dmol3程序广义梯度近似PBE泛函,系统研究了Co_(n)(n=1~5)团簇及其对分子氧(O_(2))(垂直和平行)吸附后的Co_(n)O_(2)团簇几何结构、稳定性和电子性质。结果表明:Co_(n)团簇的结合能随团簇数目的增加而增大,变化趋势趋于平缓,稳定性增强;分子氧在Co_(n)团簇顶位、桥位、空位的吸附稳定性、Co—O键长、O—O键长、分子氧的电荷转移都随团簇数目增大呈现规律性变化,说明分子氧被活化;Co_(n)团簇和分子氧之间的电荷转移越多,相互作用越强,吸附能和结合能也越大;分子氧垂直吸附型Co2O_(2)B团簇的吸附能和结合能最强,分别是-6.744 eV和4.611 eV,分子氧所得电荷最强为-1.130 e。

The geometry,stability,and electronic properties of Co_(n)(n=1~5)clusters and Co_(n)O_(2)clusters are calculated by density functional theory(DFT)with Dmol3 program by using the generalized gradient approximation PBE functionals.Co_(n)O_(2)clusters are constituted by adsorption of Co_(n)(n=1~5)clusters and molecular oxygen(O_(2))(vertical and parallel method).The results verify that the binding energy of Co_(n)clusters increases with the increase in the number of clusters,and the changing trend tends to be gentle with increasing stability.The adsorption stability,Co-O bond length,O-O bond length,and charge transfer of molecular oxygen at the top site,bridge site,and hole site of the Co_(n)clusters show regular changes,indicating that molecular oxygen is activated.The more charge transfer from Co_(n)cluster to molecular oxygen,the stronger interaction and the bigger adsorption and binding energy.The adsorption energy and binding energy of the Co_(2)O_(2)B clusters with molecular oxygen vertical adsorption type are the strongest,which are-6.744 eV and 4.611 eV,respectively,and the obtained charge of molecular oxygen is-1.130 e.