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 (XM) atoms on MgO(001) surfaces with surface-functional hydroxyl groups. The adsorption, diffusion, bonding, and electronic structure of XM on these surfaces are presented. The results indicate a large energy gain in the adsorption of XM on MgOhdr(001) with respect to XM on MgO(001). This suggests that the adsorption of XM is stronger on MgOhdr(001). Further analysis shows that in the presence of surface hydroxyl groups, XM atoms preferentially form XMOH complexes instead of XM dimers. The surface diffusion barriers of XMOH on MgO(001) [XM on MgOhdr(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 MgOhdr(001) surfaces is expected to be different from that of Cu or Au. Finally, the electronic structures and charge rearrangements of XM on MgOhdr(001) are presented and compared with those of Au on MgOhdr(001).