Structural and Stress Response of Nanotwinned B₁₃CN under Large Strains

Boron-rich carbides with icosahedral cages as pivotal structural units, which exhibit high hardness and low density, have promising industrial applications. However, the insufficient fracture toughness of these materials hinders their engineering applications. A recent first-principles study revealed that single-crystal B13CN (sc-B13CN) exhibits interesting structural deformation modes and superior mechanical properties to boron-rich carbides, prompting us to further explore this intriguing material. Herein, we adopted sc-B13CN as an archetypal system owing to its excellent structural and mechanical properties to construct nanotwinned B13CN (nt-B13CN) and explore its mechanical properties and structural deformation modes under large strains. We unraveled the specific stress-strain relationship of nt-B13CN and the considerable effect of twinning on its structural deformation modes under diverse loading conditions. Our results indicate that twinning leads to interesting structural deformation patterns and is extremely beneficial to improving the structural stability and mechanical properties of boron-rich materials. The current results provide an improved understanding of the theoretical design for various nanotwinned boron-rich materials with intricate bonding configurations.