Comprehensive study of the potential energy surface minima of a monolayer on (111) surface

摘要

The potential energy landscape of a monolayer adsorbed on well-ordered (111) surface is analyzed for periodic cells with a variable number of adsorbate (N_(ads)) and substrate (N_(sub)) particles. The atom-surface potential is described by the first Fourier series term with variable corrugation, while the lateral interaction in the monolayer is modeled by a repulsive exponential term. Special attention is devoted to the determination of the total number of minima for given N_(ads) and N_(sub) and the probability of relaxation to the global minimum in each of the unit cells, as well as the construction of the lowest energy versus coverage curve as a function of the atom-surface potential corrugation. We find that the global appearance of the energy landscape in the majority of the unit cells is particularly simple, characterized by the global minimum positioned in a very wide basin and the high-energy minima forming a tail structure. However, this rule is broken for several unit cells when the corrugation of the atom-surface potential becomes large, making the location of the global minimum a rather difficult task. Despite the simplicity of our model, phase transitions from commensurate to striped incommensurate to hexagonal incommensurate rotated structures are observed.