Critical- and Wetting-Phenomena Near the Liquid-Vapour Critical Point of Metals

Our understanding of the liquid-vapour equilibrium in metallic systems has increased enormously in the past two decades. Much of this has been stimulated by a series of pioneering papers of Mott [1] on the metal-non-metal transition which shows up when a liquid metal is heated to the region of the liquid-vapour critical point. The existence of this transition implies that the liquid-vapour phase transition of fluid metals is distinct from that of normal insulating fluids such as inert gases. An inert-gas atom retains its identity in the condensed phase and the pair potential which determines the properties of the dilute vapour phase is supplemented to a limited degree by many-body interactions, in the total potential energy of the dense phase [2]. In contrast, the electronic structures of the two coexisting phases, liquid and vapour, of fluid metals may be vastly different. The essntial point is that the metallic state is a collective phenomenon existing only when the density of atoms is sufficiently large. Unlike inert gases the electronic stucture in the high-density liquid is very different from that of an atom in the dilute vapour.