Ab initio molecular dynamics simulation of the Ag(111)-water interface

Abstract

The results of a first-principles study of the structure of the Ag(111)–water interface are presented. The calculations were carried out using an ab initio Car–Parrinello molecular dynamics simulation within a pseudopotential formalism and the generalized gradient approximation to the exchange-correlation potential. Periodic five layer slabs covered with 48 water molecules were employed to simulate the structure of the interface. An analysis of the structural properties of the interface shows that the preferable places of residence of ${\mathrm{H}}_{\mathrm{2}}\mathrm{O}$ molecules in the contact overlayer are the metal top sites. The electronic structure of the interface has also been explored. It was found that there is a strong coupling of the water overlayer with the metal crystal electronic states. However, the surface-state charge density is only slightly disturbed by the presence of water. The empty surface states are seen to not be quenched by the presence of water, which is in qualitative agreement with existing experiments. The electrons donated to the metal by the water fill the metal crystal electronic states, which is responsible for the dominant coupling of the metal with the water system.