The strain at which this occurs can be thus obtained by solving for ϵ pt y in a quadratic equation by setting r 1 = r fm To determine the strain at which the bond force is the maximum, we use a two-atom simulation between two bonded phosphorus atoms, as shown in Fig. , where ϵ xx = ϵ yy = ϵ zz = ϵ; the force is then calculated by differentiating the energy per atom with respect to the applied strain: F = ∂E ∂ϵ . As shown in Fig. , the maximum force occurs at ϵ f = 0.26. Beyond the maximum force point, the bond has undergone too much strain and fractures. Below it, bond formation is favorable. This provides us with a measure of critical bond lengths r fm = 1.26 × r 1 = 1.26 × 2.26 = 2.84 Å or r fm = 1.26 × r 2 = 1.26 × 2.29 = 2.89, which are much higher than the maximum first-neighbor bond length (of 2.58 Å) but closer to the minimum second-neighbor bond length (of 3.10 Å) at the transition state. Thus, as the second-neighbor bond length becomes comparable to r fm , it experiences a strong attractive force to form a firstneighbor bond. Given first-neighbor bond lengths (r 1n ) and second-neighbor bond lengths (r 2n ), it can therefore be asserted that the general criteria for a lattice to undergo the structural phase transition at strain ϵ c are: In the Density of States graph Fig. , we observe a drastic change in the electronic structure of the phosphorene layer before and after the phase transition, with the appearance of band gap after the transition. As a band gap within phosphorene is only characteristic of a system with little or no strain applied, the restoration of the band gap shows that the system is relaxing. From such, the material's electronic transitions from metal to semiconductor.