Surface dynamics of Cu and Ag atoms on hydroxylated MgO(001) surfaces

Density-functional theory calculations were performed to investigate the surface dynamics of Cu and Ag (X_M) atoms on MgO(001) surfaces with surface-functional hydroxyl groups. The adsorption, diffusion, bonding, and electronic structure of X_M on these surfaces are presented. The results indicate a large energy gain in the adsorption of X_M on MgO_hdr(001) with respect to X_M on MgO(001). This suggests that the adsorption of X_M is stronger on MgO_hdr(001). Further analysis shows that in the presence of surface hydroxyl groups, X_M atoms preferentially form X_MOH complexes instead of X_M dimers. The surface diffusion barriers of X_MOH on MgO(001) [X_M on MgO_hdr(001)] are calculated. CuOH is found to have a higher surface diffusion energy barrier than AgOH, but a slightly lower energy barrier to diffusion than AuOH. Therefore, sintering of Ag on MgO_hdr(001) surfaces is expected to be different from that of Cu or Au. Finally, the electronic structures and charge rearrangements of X_M on MgO_hdr(001) are presented and compared with those of Au on MgO_hdr(001).