Formation Mechanism of Phosphorus on the Ag(111) Surface: From Atomic Chains to Pentamers and Blue Phosphorene

The synthesis of blue phosphorene (BLP), a two-dimensional (2D) allotrope of phosphorus, has attracted great attention in the last ten years. During the efforts of synthesizing BLP, three distinctive phases of phosphorus on the Ag(111) surface, phosphorus chains (PCs), phosphorus pentamers (PPs), and small BLP islands, have been observed while their formation mechanisms gained a deeper understanding based on previous studies. Here, by using the highly accurate machine learning force field (MLFF), we have successfully reproduced the three phases of phosphorus on the Ag(111) surface by molecular dynamic (MD) simulations. Our simulation shows that, on a Ag(111) surface, (i) PCs are more stable than both PPs and BLP at low coverage; (ii) with the increase of the coverage of phosphorus, the formation of PCs becomes less stable than the PPs at medium concentration; and (iii) further increasing the phosphorus coverage leads to the fusion of the pentamers, the nucleation of 2D BLP islands, and a transition from PPs to a BLP layer on the Ag(111) surface. The formation mechanisms revealed by the MLFF agree precisely with numerous experimental observations and thus show that the mechanisms revealed by theoretical studies empowered by the MLFF can be used to guide the experimental design of materials synthesis.