Theoretical prediction of a novel 2D TiOBr monolayer with negative Poisson's ratio using first-principles calculations

Two-dimensional (2D) materials with novel mechanical behaviors and electronic characteristics have attracted extensive attention in multiple cutting-edge fields in recent years. Based on first-principles calculations, we systematically investigate the mechanical properties and electronic characteristics of transition metal oxyhalide TiOBr in this work. Results demonstrate that the TiOBr monolayer exhibits metallic characteristics with Dirac points located above the Fermi level. The calculated Fermi velocity of 0.32 × 10⁶ m s^-1 indicates its superior electron mobility. Furthermore, the TiOBr monolayer displays a negative Poisson's ratio (NPR) effect, establishing it as a promising candidate for auxetic materials. These distinctive properties endow the TiOBr monolayer with significant research value and application prospects in future nanoelectronics and mechanical functional materials.