Ab initio study of the mechanical and electronic properties of 2D B₂CX (X = O, S, Se) monolayers

Electronic structures and mechanical properties of two-dimensional B₂CX (X=O, S, Se) monolayers were calculated using ab initio calculations. The monolayers of B₂CO, B₂CS, and B₂CSe are indirect semiconductors with band gaps of 1.69 eV (2.88 eV), 1.17 eV (2.23 eV) and, 0.33 eV (1.23 eV) calculated by using the generalized gradient approximation in density functional theory (hybrid functional theory), respectively. Also, to study the mechanical elastic parameters of three nanostructures, we investigate the deformation in the harmonic elastic region. B₂CO is found to have comparative mechanical performance as compared to B₂CS and B₂CSe. In particular, B₂CO has the highest in-plane stiffness value, so the calculated in-plane stiffness for B₂CO is 335 N/m, and for B₂CS and B₂CSe is 297 N/m, and 253 N/m, respectively. The monolayers B₂CS and B₂CSe exhibit the negative Poisson's ratio values, giving them promising applications as auxetic materials in nanomechanics and nanoelectronics. It is also found that the electrical properties of B₂CX monolayers are modified by applying strain. (author)