Mercury Adsorption on Ni(111)

Abstract

Mercury is an ideal adsorbate with which to study the relationship between surface structure, surface electronic structure and surface thermodynamics. It is metallic, has an easily manageable mono-atomic vapour at room temperature, and forms a weak chemisorption bond with many metal surfaces such as Fe (100), [1], W (100), [2,3], Ni(l00), [4], Cu(100), [5] and a particularly weak bond with Ag(100), [6,7]. This enables equilibrium adsorption isotherms [1,3,4] to be measured at moderate temperatures (100-200°C), from which surface thermodynamic quantities may be determined. Mercury therefore bridges the gap between the detailed thermodynamic studies of noble gas physisorption on transition metals, and the structural and electronic studies of metal on metal systems, where the use of metal evaporation sources and the strong chemisorption bond involved, preclude the measurement of equilibrium adsorption isotherms. In this paper the relationship between the surface structure and the isosteric heat of adsorption (q_st) is discussed for mercury adsorbed on Ni(111).