Density functional theory study of mercury adsorption on metal surfaces

Abstract

Density functional theory (DFT) calculations are used to characterize the interaction of mercury with copper, nickel, palladium, platinum, silver, and gold surfaces. Mercury binds relatively strongly to all the metal surfaces studied, with binding energies up to $\ensuremath{\sim}1\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ for Pt and Pd. DFT calculations underestimate the energy of adsorption with respect to available experimental data. Plane-wave DFT results using the local density approximation and the Perdew-Wang 1991 and Perdew-Burke-Ernzerhof parametrizations of the generalized gradient approximation indicate that binding of mercury at hollow sites is preferred over binding at top or bridge sites. The interaction with mercury in order of increasing reactivity over the six metals studied is $\mathrm{Ag}<\mathrm{Au}<\mathrm{Cu}<\mathrm{Ni}<\mathrm{Pt}<\mathrm{Pd}$. Binding is stronger on the (001) faces of the metal surfaces, where mercury is situated in fourfold hollow sites as opposed to the threefold hollow sites on (111) faces. In general, mercury adsorption leads to decreases in the work function; adsorbate-induced work function changes are particularly dramatic on Pt.