The properties of Irn (n = 2–10) clusters and their nucleation on γ-Al2O3 and MgO surfaces: from ab initio studies. Issue 3 (2nd December 2014) - Chen, Yongchang
Abstract : The adsorption and nucleation of Ir clusters on γ-Al2 O3 (001) and MgO(100) based on first-principles calculations. Abstract : The structural stability and magnetic properties of iridium clusters Ir n ( n = 2–10) and their interaction on γ-Al2 O3 (001) and MgO(100) surfaces have been investigated from first principles calculations. It is found that the adsorption energy of Ir n ( n = 2–10)/γ-Al2 O3 (001) is lower than that of Ir n /MgO(100); meanwhile, the strongest adsorption energy cluster for γ-Al2 O3 (001) is the tetrahedral Ir4 cluster, while for MgO(100) is a cubic Ir8 cluster. On the other hand, the nucleation of Ir n ( n = 2–10) clusters on both surfaces is thermodynamically favorable and exothermic. Moreover, the nucleation energy of Ir n ( n = 2–10) clusters on the γ-Al2 O3 (001) surface is close to the corresponding energy on the MgO(100) surface, except for Ir3, Ir4 and Ir6 clusters. Interestingly, the nucleation of Ir3 and Ir6 clusters on the MgO(100) surface is more favorable than that on the γ-Al2 O3 (001) surface, while the nucleation of the Ir4 cluster is reverse and very close to the gas phase Ir4 cluster. More importantly, deformation energy and charge density analysis show that the adsorbed Ir4 cluster on the γ-Al2 O3 (001) surface has obviously charge transfer between Ir atoms and surface Al, O atoms with negligible deformation. However, for the MgO(100) surface, the Ir4 cluster connects directly to three surface O atoms with severe distortion, which inhibits the activity of the tetrahedral Ir4 cluster as a catalyst.