On the other hand, loading tensile strain up to 6%, the monolayer shows consistent mechanical stability. Remarkably, from 2% of strain, the negative Poisson's ratio (NPR) is noticed with a monotonic reduction in Young's and shear moduli. The monolayer softens (Y=172 N/m) and possesses the largest value of NPR (-0.047) at 6% of strain. The early signature of negative Poisson's ratio is indicated by rigidity in B-N and C1-N bonds (Fig. ) and consistency in cohesive energy (Fig. ) with applied strain. These basic requirements support the occurrence of NPR . However, more advanced testing can be done . The NPR behavior is very rare in 2D materials. Materials possessing such behavior are often called auxetic materials or mechanical metamaterials, which are very important in multiple applications such as tension activatable substrates, nanoauxetic materials, deformable variable stiffness materials . The NPR is also reported in strain-free penta graphene indicating the broad application of this behavior. Converse to compressive strain, the anisotropy indices, A , A Ranganathan , and A Kube , approach to smaller values indicating the reduction in anisotropy. At 6% of strain, the monolayer shows a highly elastically isotropic response. This fact is visualized by the polar plots (Fig. ), in which the curves of Young and Shear moduli, and Poisson's ratio gradually approach to be a perfect circle, indicating the anisotropy to isotropy transformation of the monolayer, with the increase in tensile strain. Therefore, diverse and unique mechanical behaviors are unraveled in p-BCN monolayer with the application of strain, which is in broad interest scientifically and technologically .