Phase transformation in two-dimensional crystalline silica under compressive loading

Using molecular dynamics simulations, we report a novel phase transformation from the hexagonal structure to the distorted structure in two-dimensional (2D) crystalline bilayer silica under uniaxial compression. In particular, the transformed distorted structures are found to be topographically different when the 2D silica is compressed in the zigzag and armchair directions, respectively. The compression-induced phase transformation has important implications for the physical responses of 2D silica. It is shown that the Young's modulus, Poisson's ratio and thermal conductivity of 2D silica are all greatly reduced after it transitions from the parent hexagonal phase to the transformed distorted phase. Moreover, we also find that the aforementioned material properties of 2D silica become strongly anisotropic after the phase transformation, in contrast to the isotropic material properties observed in the parent hexagonal phase of 2D silica.