Thermal decomposition of a honeycomb-network sheet: a molecular dynamics simulation study

The thermal degradation of a graphene-like two-dimensional honeycomb membrane with bonds undergoing temperature-induced scission is studied by means of Molecular Dynamics simulation using Langevin thermostat. We demonstrate that at lower temperature the probability distribution of breaking bonds is highly peaked at the rim of the membrane sheet whereas at higher temperature bonds break at random everywhere in the hexagonal flake. The mean breakage time τ is found to decrease with the total number of network nodes N by a power law τ ∝ N(-0.5) and reveals an Arrhenian dependence on temperature T. Scission times are themselves exponentially distributed. The fragmentation kinetics of the average number of clusters can be described by first-order chemical reactions between network nodes n(i) of different coordination. The distribution of fragments sizes evolves with time elapsed from initially a δ-function through a bimodal one into a single-peaked again at late times. Our simulation results are complemented by a set of 1st-order kinetic differential equations for n(i) which can be solved exactly and compared to data derived from the computer experiment, providing deeper insight into the thermolysis mechanism.