where, E represents the total energy of a monolayer and represents the total energy of isolated atoms with as the number of a specific atom per monolayer. B , C , and N represent the chemical potential of respective atoms. The x, y and, z represent the number of B, C, and N atoms in unit cell, respectively. Further, we adopt the density-functional perturbation theory (DFPT) implemented in Quantum-Espresso package for the calculations of the phonon dispersions of the monolayer. We obtain an accurate force matrix with 5 × 5 × 1 supercell. For optical properties calculations, a denser k-point mesh, i.e. 60 × 60 × 1, within the Monkhorst-Pack scheme and optical broadening of 0.1 eV is used. Optical calculations in SIESTA are based on the first order time dependent perturbation theory (TDP) .