Molecular Dynamics Simulations of the Surface Reconstructions of Pt(557) and Au(557) under Exposure to CO

The mechanism and dynamics of surface reconstructions of Pt(557) and Au(557) exposed to various coverages of carbon monoxide (CO) were investigated using molecular dynamics simulations. Metal–CO interactions were parametrized from experimental data and plane-wave density functional theory (DFT) calculations. The large difference in binding strengths of the Pt–CO and Au–CO interactions was found to play a significant role in step-edge stability and adatom diffusion constants. Various mechanisms for CO-mediated step wandering and step doubling were investigated on the Pt(557) surface. We find that the energetics of CO adsorbed to the surface can explain the step-doubling reconstruction observed on Pt(557) and the lack of such a reconstruction on the Au(557) surface. However, more complicated reconstructions into triangular clusters that have been seen in recent experiments were not observed in these simulations.