Max Planck Institute for Polymer Research, 10 Ackermannweg, 55128 Mainz, Germany.
J Chem Phys. 2012 Aug 7;137(5):054901. doi: 10.1063/1.4739536.
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.
采用基于朗之万方程的分子动力学模拟方法，研究了在热诱导键断裂条件下，具有类石墨烯二维蜂窝状膜的热降解过程。我们证明，在较低温度下，键断裂的概率分布在膜片的边缘处高度集中，而在较高温度下，六边形薄片中的任意位置的键都会随机断裂。平均断裂时间 τ 发现与网络节点总数 N 呈幂律关系 τ∝N(-0.5)，并且对温度 T 呈 Arrhenius 依赖性。断裂时间本身呈指数分布。平均簇数的碎片动力学可以通过不同配位数的网络节点 n(i)之间的一级化学反应来描述。碎片尺寸的分布随着初始的 δ 函数随时间的流逝而演变，经过双峰分布，最后再次演变为单峰分布。我们的模拟结果由一组一阶动力学微分方程补充，这些方程可以精确求解，并与从计算机实验中得出的数据进行比较，从而深入了解热解机制。
