Two-dimensional metal structures revealed by evolutionary computations: Pb/Al13Co4(100) as a case study

Abstract

We have combined extensive density functional theory calculations with an evolutionary algorithm to investigate possible structural models for two-dimensional (2D) Pb films supported on the Al13Co4(100) quasicrystal approximant surface. The minimization of the total energy while maximizing the atomic density in the layer leads to 2D atomic arrangement with pentagonal motifs, reflecting the symmetry of the substrate. Our findings show that the 2D structure can be interpreted as a stable structure with 16 Pb atoms per surface cell in the film, in line with the measured coverage. This conclusion is also supported by the reasonable agreement between the experimental scanning tunneling microscopy images and those simulated using this structural model. Alternatively, a metastable 2D film made of 15 Pb atoms fits with the experimental observations. This study opens a route toward the prediction of supported complex 2D films.