Synthesizable Two-Dimensional Haeckelites with Auxetic Behavior and Multifunctional Properties: A Computational Study Integrating Machine Learning Interatomic Potentials

Our recent high-throughput investigation has uncovered bulk semiconducting haeckelite structures that hold considerable promise for optoelectronic applications ( Advanced Functional Materials, 10.1002/adfm.202402390). In this study, we perform a comprehensive search using evolutionary algorithms alongside first-principles simulations to identify stable two-dimensional haeckelite structures. This process reveals the presence of two-dimensional CdS, CdSe, ZnSe, and ZnTe haeckelites. We analyze the phonon dispersion relations and lattice thermal conductivity by utilizing machine learning interatomic potentials. The resulting nanosheets demonstrate a dynamic stability and exceptional mechanical properties. Additionally, they exhibit low lattice thermal conductivity ranging from 3 to 30 W/mK, with band gaps of 2.1 to 2.8 eV. Notably, the CdS and CdSe haeckelite structures show high electron and hole mobilities along with strong visible light absorption, making them highly suitable for optoelectronic applications. A particularly intriguing discovery is their negative Poisson's ratio in all directions, indicating auxetic characteristics.