Exploring environment-dependent shape evolution in Bi₂Se₃ nano-crystallites: A first-principles thermodynamics approach

Bismuth selenide (Bi₂Se₃) has attracted much interest and has found niche applications in various fields of thermoelectrics, topologically non-trivial systems, as well as in progressive radiotherapy medical treatments. Until recently, the solution-based solvothermal method has been shown to be a very promising way to achieve high scalability and crystallinity for cost-effective large-scale production. By carefully controlling the experimental conditions, the shape and size can be manipulated. However, there is still a lack of understanding regarding the underlying mechanism that governs the preferred shape growth where classical models (e.g. Lamer model) cannot provide a complete explanation. In this work, we perform first-principles calculations and model the environment-dependent shape evolution of Bi₂Se₃ nanocrystals with the Gibbs-Wulff theorem. Here, we examine how the various growth conditions (e.g. defects, precursor, solvent, etc.) can contribute to the thermodynamic shape evolution and predict/explain experimentally observed morphologies of Bi₂Se₃.