) of the monolayer. The strain is applied from -2% to 2% for each direction with an increment of 1%. For each iteration of strain, the atomic positions of the system is fully relaxed. Further, the result is fitted to the strain energy, = 1 2 + 2 2 + 3 . Here, 1 , 2 and 3 are three constants that are obtained during the fitting process. Due to the isotropy in the honeycomb symmetry, 1 is equal to 2 . The 3D surface fit (Fig. ) shows the distribution of strain energy with respect to the different possible value of applied strain. The maximum strain energy value is lower in FBNF predicting the relatively smaller mechanical strength. The preceding expression is also obtained from elasticity matrix in terms of elastic stiffness constants 11 and 12 by employing 11 = 2 1 ∕ 0 and 12 = 3 ∕ 0 where A 0 is strain-free area of the monolayer. The 11 and 12 are only two significant independent elastic stiffness coefficients . Another calculated elastic constant, C 66 is (C 11 -C 12 )/2. The in-plane stiffness (C) and Poisson's ratio( ) are represented by 11 × [1 -( 12 ∕ C 11 ) 2 ] and 12 ∕ 11 , respectively. In 2D materials, the bulk modulus which gives a measure of the material's resilience to an external biaxial strain is calculated in terms of layer modulus ( ) with the expression, = (C 11 +C 22 +2C 12 )/4. In addition, using these second-order elastic constants C , the shear modulus, K=C/2(1-), is calculated. The shear modulus estimates the resistance of the material to the shear strain. Further, the in-plane stiffness and Poisson's ratio are used to test the mechanical anisotropy. They are functions of the direction angles , which can be represented as : ). The in-plane stiffness of the FBNF is 168.33 N/m, less than h-BN (266.29 N/m ) indicating the softening. Similarly, the Poisson's ratio of FBNF is 0.17, also not more than h-BN (0.21 ) but comparable to graphene indicating reduction in sensitivity toward uniaxial strain. Similarly, the shear (K) and layer moduli ( ) are 71.70 N/m and 110.88 N/m, respectively. These values are also smaller than h-BN indicating the less resilient material. The physics behind the decrease in the value of mechanical parameter after fluorination in the h-BN (FBNF) is attributed to the decrease in cohesive energy per atom and elongation in B-N covalent bond. Further, the directional dependency of in-plane stiffness and Poisson's ratio is checked by polar plot fit using Equ. 5. From the polar plot shown in Fig. , the Poisson ratio and in-plane stiffness for FBNF is a perfect circle, similar to h-BN, indicates elastic isotropy. The computed mechanical parameters are very close to both experimental and theoretical reports (Table ). It's worth in mentioning that similar results are computed by previous report in hydrogen passivated hexagonal GeC monolayer .