Melting of a quasi-two-dimensional metallic system - art. no. 051502

We analyze the melting of a quasi-two-dimensional metallic system using the results of a series of Monte Carlo simulations of an array of Pb atoms. Th e system was chosen to model the melting behavior observed for the monolaye r of Pb that segregates in the liquid-vapor interface of a dilute Pb in Ga alloy [B. Yang Et al., Proc. Natl. Acad. Sci. USA 96, 13 009 (1999)]. Our c alculations employed a realistic pair interaction potential between lead ps eudoatoms, one that is known to describe accurately the properties of the t hree-dimensional metal near the melting point. Our results reveal that in t he quasi-two-dimensional Pb system melting is a two-stage process which pro ceeds through formation of a stable intermediate heretic phase, in agreemen t with the prediction of the Kosterlitz-Thouless-Halperin-Nelson-Young theo ry. Both the solid-to-heretic and the hexatic-to-liquid transitions are fou nd to be first order in our simulations.