Evolutionary Pathways of T-Phase Transition Metal Dichalcogenides: A Comprehensive Study of Pt x Se y Clusters.

Understanding the transition from nonplanar to planar clusters is crucial for the controllable synthesis of transition metal dichalcogenide (TMDC) monolayers. Using PtSe 2 as a model, we investigate how the chemical environment influences the nucleation and growth stages of monolayer PtSe 2 through structure searching and first-principles calculations. We established a comprehensive database of platinum selenide clusters (Pt x Se y , x = 1-10), analyzing 2095 unique clusters and identifying 191 stable isomers and 63 structures with the lowest formation energy on the convex hull. Our findings reveal a chemical environment-dependent phase transition from 3D structures to the planar T-phase of Pt x Se y clusters, representing an evolutionary route for PtSe 2 growth. Clusters such as PtSe 6 , Pt 2 Se 9 , Pt 3 Se 10 , and Pt 7 Se 10 in Pt-rich environments, as well as Pt 2 Se 15 and Pt 10 Se 32 in Se-rich environments, have been found to exhibit high stability. Additionally, the impact of varying chemical potentials of Pt and Se on the stability of these clusters is explored. PtSe 4 and PtSe 6 are found to be highly stable under most experimentally achievable chemical potential conditions and may serve as dominant precursors during PtSe 2 growth. This work advances our understanding of the nucleation processes of PtSe 2 and other T-phase TMDC materials.