Computational Prediction of Novel Two-Dimensional Selenium Allotropes

Two-dimensional (2D) materials have attracted much attention due to their potential applications in the next-generation electronic and optoelectronic fields. By integrating the particle swarm optimization method and first-principles calculations based on density functional theory (DFT), we predicted 8 novel 2D Se allotropes. Their dynamic and thermal stabilities have been verified by phonon spectrum calculations and ab initio molecular dynamics simulations (AIMD), respectively. Our calculation results show that these new 2D Se allotropes exhibit rich electronic properties, including metallic, semiconducting, and topological insulator properties, and several of them have high carrier mobility. Besides, the effect of strain on electronic properties of some semiconducting selenene phases has also been systematically studied. The optical calculations show that these new 2D Se phases with semiconducting properties have strong optical absorption in the visible light region. These results enlarge the family of selenene and will stimulate more researchers to take efforts on the field of group-VI 2D materials.