Energy density analysis of cluster size dependence of surface-molecule interactions (II): Formate adsorption onto a Cu(111) surface

Adsorption of formate (HCOO) onto a Cu(111) surface has been treated theoretically using 18 kinds of Cu_n (6 ≤ n ≤ 56) clusters. The energy density analysis (EDA) proposed by Nakai has been adopted to examine surface-molecule interactions for different cluster sizes. EDA results for the largest model cluster Cu₅₆ have shown that the adsorption-induced energy density variation in Cu atoms decays with distance from the adsorption site. Analysis of this decay, which can be carried out using the EDA technique, is important because it enables verification of the reliability of the model cluster used. In the case of formate adsorption onto the Cu(111) surface, it is found that at least a four-layer model cluster is necessary to treat the surface-molecule interaction with chemical accuracy.