Three-Dimensional Porous Borocarbonitride Bc2n With Negative Poisson'S Ratio

Motivated by the recent synthesis of three-dimensional (3D) porous borocarbonitride (Angew. Chem., Int. Ed., 2019, 58, 6033-6037), we propose a porous 3D-BC2N structure composed of BC2N nanoribbons. On the basis of detailed theoretical analysis and calculations, we find that the porous 3D-BC2N is dynamically stable with cohesive energy of 9.52 eV per atom and a Zener anisotropic factor of 2.72. This system exhibits a Pugh's ratio of 0.529 and hardness of 23.9 GPa, it also shows an indirect band gap of 2.056 eV with good absorption in ultraviolet regions. More importantly, the porous 3D-BC2N is found to be the first borocarbonitride with a negative Poisson's ratio of -0.08. Our study expands the borocarbonitride family with new features.